Journal articles
McDonagh STJ, Wylie LJ, Morgan P, Vanhatalo A, Jones A (In Press). A randomised controlled trial exploring the effects of different beverages consumed alongside a nitrate-rich meal on systemic blood pressure. Nutrition and Health
Jones AM (In Press). All-out vs. constant work rate exercise: effects on muscle efficiency. J Appl Physiol
Bailey SJ, Vanhatalo A, Black MI, DiMenna FJ, Jones AM (In Press). Effects of priming and pacing strategy on VO2 kinetics and cycling performance.
Burnley M, Vanhatalo A, Fulford J, Jones AM (In Press). High-energy phosphate responses to maximal and submaximal intermittent isometric quadriceps contractions assessed using 31P-MRS in humans. J Appl Physiol
Vanhatalo A, Fulford J, Jones AM (In Press). Influence of hyperoxia on the power-duration relationship and muscle metabolism during severe intensity exercise. Am J Physiol Regul Integr Comp Physiol
Jones AM, Wilkerson DP, Fulford J (In Press). Influence of muscle temperature on muscle metabolic response to exercise. J Appl Physiol
Jones AM, Krustrup P (In Press). Muscle O2 uptake and blood flow kinetics. J Appl Physiol
Kadach S, Park JW, Stoyanov Z, Black MI, Vanhatalo A, Burnley M, Walter PJ, Cai H, Schechter AN, Piknova B, et al (2023). 15 N-labeled dietary nitrate supplementation increases human skeletal muscle nitrate concentration and improves muscle torque production.
Acta Physiol (Oxf),
237(3).
Abstract:
15 N-labeled dietary nitrate supplementation increases human skeletal muscle nitrate concentration and improves muscle torque production.
AIM: Dietary nitrate (NO3 - ) supplementation increases nitric oxide bioavailability and can enhance exercise performance. We investigated the distribution and metabolic fate of ingested NO3 - at rest and during exercise with a focus on skeletal muscle. METHODS: in a randomized, crossover study, 10 healthy volunteers consumed 12.8 mmol 15 N-labeled potassium nitrate (K15 NO3 ; NIT) or potassium chloride placebo (PLA). Muscle biopsies were taken at baseline, at 1- and 3-h post-supplement ingestion, and immediately following the completion of 60 maximal intermittent contractions of the knee extensors. Muscle, plasma, saliva, and urine samples were analyzed using chemiluminescence to determine absolute [NO3 - ] and [NO2 - ], and by mass spectrometry to determine the proportion of NO3 - and NO2 - that was 15 N-labeled. RESULTS: Neither muscle [NO3 - ] nor [NO2 - ] were altered by PLA. Following NIT, muscle [NO3 - ] (but not [NO2 - ]) was elevated at 1-h (from ~35 to 147 nmol/g, p
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Hassan EK, Jones AM, Buckingham G (2023). A novel protocol to induce mental fatigue.
Behavior Research MethodsAbstract:
A novel protocol to induce mental fatigue
AbstractMental fatigue is a commonplace human experience which is the focus of a growing body of research. Whilst researchers in numerous disciplines have attempted to uncover the origins, nature, and effects of mental fatigue, the literature is marked by many contradictory findings. We identified two major methodological problems for mental fatigue research. First, researchers rarely use objective measures of mental fatigue. Instead, they rely heavily on subjective reports as evidence that mental fatigue has been induced in participants. We aimed to develop a task which led to not only a subjective increase in mental fatigue, but a corresponding performance decrement in the mentally fatiguing task as an objective measure. Secondly, current mental fatigue paradigms have low ecological validity – in most prior studies participants have been fatigued with a single repetitive task such as the n-back or Stroop. To move towards a more ecologically valid paradigm, our participants undertook a battery of diverse cognitive tasks designed to challenge different aspects of executive function. The AX-CPT, n-back, mental rotation, and visual search tasks were chosen to challenge response inhibition, working memory, spatial reasoning, and attention. We report results from 45 participants aged 19 to 63 years who completed a two-hour battery comprising four different cognitive tasks. Subjective fatigue ratings and task performance were measured at the beginning and end of the battery. Our novel method resulted in an increase in subjective ratings of fatigue (p < 0.001) and a reduction in task performance (p = 0.008). Future research into mental fatigue may benefit from using this task battery.
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Black MI, Skiba PF, Wylie LJ, Lewis J, Jones AM, Vanhatalo A (2023). Accounting for Dynamic Changes in the Power-Duration Relationship Improves the Accuracy of W' Balance Modeling.
Med Sci Sports Exerc,
55(2), 235-244.
Abstract:
Accounting for Dynamic Changes in the Power-Duration Relationship Improves the Accuracy of W' Balance Modeling.
PURPOSE: This study aimed 1) to examine the accuracy with which W' reconstitution (W' REC ) is estimated by the W' balance (W' BAL ) models after a 3-min all-out cycling test (3MT), 2) to determine the effects of a 3MT on the power-duration relationship, and 3) to assess whether accounting for changes in the power-duration relationship during exercise improved estimates of W' REC. METHODS: the power-duration relationship and the actual and estimated W' REC were determined for 12 data sets extracted from our laboratory database where participants had completed two 3MT separated by 1-min recovery (i.e. control [C-3MT] and fatigued [F-3MT]). RESULTS: Actual W' REC (6.3 ± 1.4 kJ) was significantly overestimated by the W' BAL·ODE (9.8 ± 1.3 kJ; P < 0.001) and the W' BAL·MORTON (16.9 ± 2.6 kJ; P < 0.001) models but was not significantly different to the estimate provided by the W' BAL·INT (7.5 ± 1.5 kJ; P > 0.05) model. End power (EP) was 7% lower in the F-3MT (263 ± 40 W) compared with the C-3MT (282 ± 44 W; P < 0.001), and work done above EP (WEP) was 61% lower in the F-3MT (6.3 ± 1.4 kJ) compared with the C-3MT (16.9 ± 3.2 kJ). The size of the error in the estimated W' REC was correlated with the reduction in WEP for the W' BAL·INT and W' BAL·ODE models (both r > -0.74, P < 0.01) but not the W' BAL·MORTON model ( r = -0.18, P > 0.05). Accounting for the changes in the power-duration relationship improved the accuracy of the W' BAL·ODE and W' BAL·MORTON , but they remained significantly different to actual W' REC. CONCLUSIONS: These findings demonstrate that the power-duration relationship is altered after a 3MT, and accounting for these changes improves the accuracy of the W' BAL·ODE and the W' BAL·MORTON , but not W' BAL·INT models. These results have important implications for the design and use of mathematical models describing the energetics of exercise performance.
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Foster C, de Koning JJ, Hettinga FJ, Barroso R, Boullosa D, Casado A, Cortis C, Fusco A, Gregorich H, Jaime S, et al (2023). Competition Between Desired Competitive Result, Tolerable Homeostatic Disturbance, and Psychophysiological Interpretation Determines Pacing Strategy.
Int J Sports Physiol Perform,
18(4), 335-346.
Abstract:
Competition Between Desired Competitive Result, Tolerable Homeostatic Disturbance, and Psychophysiological Interpretation Determines Pacing Strategy.
Scientific interest in pacing goes back >100 years. Contemporary interest, both as a feature of athletic competition and as a window into understanding fatigue, goes back >30 years. Pacing represents the pattern of energy use designed to produce a competitive result while managing fatigue of different origins. Pacing has been studied both against the clock and during head-to-head competition. Several models have been used to explain pacing, including the teleoanticipation model, the central governor model, the anticipatory-feedback-rating of perceived exertion model, the concept of a learned template, the affordance concept, the integrative governor theory, and as an explanation for "falling behind." Early studies, mostly using time-trial exercise, focused on the need to manage homeostatic disturbance. More recent studies, based on head-to-head competition, have focused on an improved understanding of how psychophysiology, beyond the gestalt concept of rating of perceived exertion, can be understood as a mediator of pacing and as an explanation for falling behind. More recent approaches to pacing have focused on the elements of decision making during sport and have expanded the role of psychophysiological responses including sensory-discriminatory, affective-motivational, and cognitive-evaluative dimensions. These approaches have expanded the understanding of variations in pacing, particularly during head-to-head competition.
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Poole DC, Jones AM (2023). Critical power: a paradigm-shift for benchmarking exercise testing and prescription.
Exp Physiol,
108(4), 539-540.
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Cocksedge SP, Causer AJ, Winyard PG, Jones AM, Bailey SJ (2023). Oral Temperature and pH Influence Dietary Nitrate Metabolism in Healthy Adults.
Nutrients,
15(3), 784-784.
Abstract:
Oral Temperature and pH Influence Dietary Nitrate Metabolism in Healthy Adults
This study tested the hypothesis that the increases in salivary and plasma [NO2−] after dietary NO3− supplementation would be greater when oral temperature and pH were independently elevated, and increased further when oral temperature and pH were elevated concurrently. Seven healthy males (mean ± SD, age 23 ± 4 years) ingested 70 mL of beetroot juice concentrate (BR, which provided ~6.2 mmol NO3−) during six separate laboratory visits. In a randomised crossover experimental design, salivary and plasma [NO3−] and [NO2−] were assessed at a neutral oral pH with a low (TLo-pHNorm), intermediate (TMid-pHNorm), and high (THi-pHNorm) oral temperature, and when the oral pH was increased at a low (TLo-pHHi), intermediate (TMid-pHHi), and high (THi-pHHi) oral temperature. Compared with the TMid-pHNorm condition (976 ± 388 µM), the mean salivary [NO2−] 1–3 h post BR ingestion was higher in the TMid-pHHi (1855 ± 423 µM), THi-pHNorm (1371 ± 653 µM), THi-pHHi (1792 ± 741 µM), TLo-pHNorm (1495 ± 502 µM), and TLo-pHHi (2013 ± 662 µM) conditions, with salivary [NO2−] also higher at a given oral temperature when the oral pH was increased (p < 0.05). Plasma [NO2−] was higher 3 h post BR ingestion in the TMid-pHHi, THi-pHHi, and TLo-pHHi conditions, but not the TLo-pHNorm and THi-pHNorm conditions, compared with TMid-pHNorm (p < 0.05). Therefore, despite ingesting the same NO3− dose, the increases in salivary [NO2−] varied depending on the temperature and pH of the oral cavity, while the plasma [NO2−] increased independently of oral temperature, but to a greater extent at a higher oral pH.
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Wei C, Vanhatalo A, Kadach S, Stoyanov Z, Abu-Alghayth M, Black MI, Smallwood MJ, Rajaram R, Winyard PG, Jones AM, et al (2023). Reduction in blood pressure following acute dietary nitrate ingestion is correlated with increased red blood cell S-nitrosothiol concentrations.
Nitric Oxide,
138-139, 1-9.
Abstract:
Reduction in blood pressure following acute dietary nitrate ingestion is correlated with increased red blood cell S-nitrosothiol concentrations.
Dietary nitrate (NO3-) supplementation can enhance nitric oxide (NO) bioavailability and lower blood pressure (BP) in humans. The nitrite concentration ([NO2-]) in the plasma is the most commonly used biomarker of increased NO availability. However, it is unknown to what extent changes in other NO congeners, such as S-nitrosothiols (RSNOs), and in other blood components, such as red blood cells (RBC), also contribute to the BP lowering effects of dietary NO3-. We investigated the correlations between changes in NO biomarkers in different blood compartments and changes in BP variables following acute NO3- ingestion. Resting BP was measured and blood samples were collected at baseline, and at 1, 2, 3, 4 and 24 h following acute beetroot juice (∼12.8 mmol NO3-, ∼11 mg NO3-/kg) ingestion in 20 healthy volunteers. Spearman rank correlation coefficients were determined between the peak individual increases in NO biomarkers (NO3-, NO2-, RSNOs) in plasma, RBC and whole blood, and corresponding decreases in resting BP variables. No significant correlation was observed between increased plasma [NO2-] and reduced BP, but increased RBC [NO2-] was correlated with decreased systolic BP (rs = -0.50, P = 0.03). Notably, increased RBC [RSNOs] was significantly correlated with decreases in systolic (rs = -0.68, P = 0.001), diastolic (rs = -0.59, P = 0.008) and mean arterial pressure (rs = -0.64, P = 0.003). Fisher's z transformation indicated no difference in the strength of the correlations between increases in RBC [NO2-] or [RSNOs] and decreased systolic blood pressure. In conclusion, increased RBC [RSNOs] may be an important mediator of the reduction in resting BP observed following dietary NO3- supplementation.
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Ashtari Esfahani A, Böser S, Buzinsky N, Carmona-Benitez M, Claessens C, de Viveiros L, Fertl M, Formaggio J, Gladstone L, Grando M, et al (2023). SYNCA: a Synthetic Cyclotron Antenna for the Project 8 Collaboration.
Journal of Instrumentation,
18(1).
Abstract:
SYNCA: a Synthetic Cyclotron Antenna for the Project 8 Collaboration
Cyclotron Radiation Emission Spectroscopy (CRES) is a technique for measuring the kinetic energy of charged particles through a precision measurement of the frequency of the cyclotron radiation generated by the particle's motion in a magnetic field. The Project 8 collaboration is developing a next-generation neutrino mass measurement experiment based on CRES. One approach is to use a phased antenna array, which surrounds a volume of tritium gas, to detect and measure the cyclotron radiation of the resulting β-decay electrons. To validate the feasibility of this method, Project 8 has designed a test stand to benchmark the performance of an antenna array at reconstructing signals that mimic those of genuine CRES events. To generate synthetic CRES events, a novel probe antenna has been developed, which emits radiation with characteristics similar to the cyclotron radiation produced by charged particles in magnetic fields. This paper outlines the design, construction, and characterization of this Synthetic Cyclotron Antenna (SYNCA). Furthermore, we perform a series of measurements that use the SYNCA to test the position reconstruction capabilities of the digital beamforming reconstruction technique. We find that the SYNCA produces radiation with characteristics closely matching those expected for cyclotron radiation and reproduces experimentally the phenomenology of digital beamforming simulations of true CRES signals.
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Jones AM (2023). The fourth dimension: physiological resilience as an independent determinant of endurance exercise performance.
J PhysiolAbstract:
The fourth dimension: physiological resilience as an independent determinant of endurance exercise performance.
Endurance exercise performance is known to be closely associated with the three physiological pillars of maximal O2 uptake (. V ̇ O 2 max. $\dot{V}_{{\rm O}_{2}{\rm max}}$. ), economy or efficiency during submaximal exercise, and the fractional utilisation of. V ̇ O 2 max. $\dot{V}_{{\rm O}_{2}{\rm max}}$. (linked to metabolic/lactate threshold phenomena). However, while 'start line' values of these variables are collectively useful in predicting performance in endurance events such as the marathon, it is not widely appreciated that these variables are not static but are prone to significant deterioration as fatiguing endurance exercise proceeds. For example, the 'critical power' (CP), which is a composite of the highest achievable steady-state oxidative metabolic rate and efficiency (O2 cost per watt), may fall by an average of 10% following 2 h of heavy intensity cycle exercise. Even more striking is that the extent of this deterioration displays appreciable inter-individual variability, with changes in CP ranging from
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Luttikholt H, Jones AM (2022). Correction to: Effect of protocol on peak power output in continuous incremental cycle exercise tests.
Eur J Appl Physiol,
122(4).
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Shannon OM, Allen JD, Bescos R, Burke L, Clifford T, Easton C, Gonzalez JT, Jones AM, Jonvik KL, Larsen FJ, et al (2022). Dietary Inorganic Nitrate as an Ergogenic Aid: an Expert Consensus Derived via the Modified Delphi Technique.
Sports Med,
52(10), 2537-2558.
Abstract:
Dietary Inorganic Nitrate as an Ergogenic Aid: an Expert Consensus Derived via the Modified Delphi Technique.
INTRODUCTION: Dietary inorganic nitrate is a popular nutritional supplement, which increases nitric oxide bioavailability and may improve exercise performance. Despite over a decade of research into the effects of dietary nitrate supplementation during exercise there is currently no expert consensus on how, when and for whom this compound could be recommended as an ergogenic aid. Moreover, there is no consensus on the safe administration of dietary nitrate as an ergogenic aid. This study aimed to address these research gaps. METHODS: the modified Delphi technique was used to establish the views of 12 expert panel members on the use of dietary nitrate as an ergogenic aid. Over three iterative rounds (two via questionnaire and one via videoconferencing), the expert panel members voted on 222 statements relating to dietary nitrate as an ergogenic aid. Consensus was reached when > 80% of the panel provided the same answer (i.e. yes or no). Statements for which > 80% of the panel cast a vote of insufficient evidence were categorised as such and removed from further voting. These statements were subsequently used to identify directions for future research. RESULTS: the 12 panel members contributed to voting in all three rounds. A total of 39 statements (17.6%) reached consensus across the three rounds (20 yes, 19 no). In round one, 21 statements reached consensus (11 yes, 10 no). In round two, seven further statements reached consensus (4 yes, 3 no). In round three, an additional 11 statements reached consensus (5 yes, 6 no). The panel agreed that there was insufficient evidence for 134 (60.4%) of the statements, and were unable to agree on the outcome of the remaining statements. CONCLUSIONS: This study provides information on the current expert consensus on dietary nitrate, which may be of value to athletes, coaches, practitioners and researchers. The effects of dietary nitrate appear to be diminished in individuals with a higher aerobic fitness (peak oxygen consumption [V̇O2peak] > 60 ml/kg/min), and therefore, aerobic fitness should be taken into account when considering use of dietary nitrate as an ergogenic aid. It is recommended that athletes looking to benefit from dietary nitrate supplementation should consume 8-16 mmol nitrate acutely or 4-16 mmol/day nitrate chronically (with the final dose ingested 2-4 h pre-exercise) to maximise ergogenic effects, taking into consideration that, from a safety perspective, athletes may be best advised to increase their intake of nitrate via vegetables and vegetable juices. Acute nitrate supplementation up to ~ 16 mmol is believed to be safe, although the safety of chronic nitrate supplementation requires further investigation. The expert panel agreed that there was insufficient evidence for most of the appraised statements, highlighting the need for future research in this area.
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Jones AM (2022). EIC Jones editorial.
Med Sci Sports Exerc,
54(1).
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Luttikholt H, Jones AM (2022). Effect of protocol on peak power output in continuous incremental cycle exercise tests.
EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY,
122(3), 757-768.
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Tan R, Wylie LJ, Wilkerson DP, Vanhatalo A, Jones AM (2022). Effects of dietary nitrate on the O-2 cost of submaximal exercise: Accounting for "noise" in pulmonary gas exchange measurements.
JOURNAL OF SPORTS SCIENCES,
40(10), 1149-1157.
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Black MI, Kranen SH, Kadach S, Vanhatalo A, Winn B, Farina EM, Kirby BS, Jones AM (2022). Highly Cushioned Shoes Improve Running Performance in Both the Absence and Presence of Muscle Damage.
Med Sci Sports Exerc,
54(4), 633-645.
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Highly Cushioned Shoes Improve Running Performance in Both the Absence and Presence of Muscle Damage.
PURPOSE: We tested the hypotheses that a highly cushioned running shoe (HCS) would 1) improve incremental exercise performance and reduce the oxygen cost (Oc) of submaximal running, and 2) attenuate the deterioration in Oc elicited by muscle damage consequent to a downhill run. METHODS: Thirty-two recreationally active participants completed an incremental treadmill test in an HCS and a control running shoe (CON) for the determination of Oc and maximal performance. Subsequently, participants were pair matched and randomly assigned to one of the two footwear conditions to perform a moderate-intensity running bout before and 48 h after a 30-min downhill run designed to elicit muscle damage. RESULTS: Incremental treadmill test performance was improved (+5.7%; +1:16 min:ss; P < 0.01) in the HCS when assessed in the nondamaged state, relative to CON. This coincided with a significantly lower Oc (-3.2%; -6 mL·kg-1·km-1; P < 0.001) at a range of running speeds and an increase in the speed corresponding to 3 mM blood lactate (+3.2%; +0.4 km·h-1; P < 0.05). As anticipated, the downhill run resulted in significant changes in biochemical, histological, and perceptual markers of muscle damage, and a significant increase in Oc (+5.2%; 10.1 mL·kg-1·km-1) was observed 48 h post. In the presence of muscle damage, Oc was significantly lower in HCS (-4.6%; -10 mL·kg-1·km-1) compared with CON. CONCLUSIONS: These results indicate that HCS improved incremental exercise performance and Oc in the absence of muscle damage and show, for the first time, that despite worsening of Oc consequent to muscle damage, improved Oc in HCS is maintained.
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Nyberg M, Jones AM (2022). Matching of O-2 Utilization and O-2 Delivery in Contracting Skeletal Muscle in Health, Aging, and Heart Failure.
FRONTIERS IN PHYSIOLOGY,
13 Author URL.
Tan R, Vanhatalo A, Jones AM (2022). Multiple Exercise Transitions Reveal Effects of Dietary Nitrate on Pulmonary Oxygen Uptake. Medicine & Science in Sports & Exercise, 54(9S), 651-651.
Reuveny R, Luboshitz J, Wilkerson D, Bar-Dayan A, DiMenna FJ, Jones AM, Segel MJ (2022). Oxygen uptake kinetics during exercise reveal central and peripheral limitation in patients with iliofemoral venous obstruction.
J Vasc Surg Venous Lymphat Disord,
10(3), 697-704.e4.
Abstract:
Oxygen uptake kinetics during exercise reveal central and peripheral limitation in patients with iliofemoral venous obstruction.
OBJECTIVE: Pulmonary oxygen uptake (V˙O2) kinetics measured during the initiation of exercise mirror energetic transition during daily activity. The aim of this study was to elucidate the pathophysiological mechanisms of exercise limitation of patients with chronic iliofemoral vein obstruction after deep vein thrombosis by measuring V˙O2 kinetics compared with patients with peripheral arterial disease (PAD) and healthy individuals. METHODS: Eleven patients with iliofemoral vein obstruction (7 men; age, 20-65 years), seven patients with PAD (all men; age 44-60 years) and eight healthy participants (5 men; age 28-58 years) were studied. Participants performed upper and lower limb symptom-limited cardiopulmonary exercise tests on cycle ergometers; and four repeat lower limb tests at a constant work rate corresponding with 90% of the gas exchange threshold for determining V˙O2 kinetics. RESULTS: Phase I V˙O2 amplitude in the constant work rate tests (percent increase over resting V˙O2), representing the initial surge in cardiac output caused by the emptying of leg veins, was 59 ± 19% in the iliofemoral vein obstruction group, 73 ± 22% in PAD, and 85 ± 26% in healthy participants (P =. 055 for iliofemoral vein obstruction vs healthy). Phase II V˙O2 kinetics, which largely reflect the kinetics of O2 consumption in the exercising muscles, were slower in iliofemoral vein obstruction (tau = 42 ± 6 seconds), and PAD (tau = 49 ± 19 seconds), compared with healthy participants (23 ± 4 seconds; P <. 01). CONCLUSIONS: Slow phase II V˙O2 kinetics reflect a slow onset of muscular aerobic metabolism in both iliofemoral vein obstruction and PAD. The low amplitude phase I of V˙O2 kinetics observed in iliofemoral vein obstruction suggests a damped cardiodynamic phase, consistent with decreased venous return from the obstructed veins. These abnormalities of V˙O2 kinetics may contribute to exercise intolerance in iliofemoral vein obstruction and PAD.
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Kadach S, Black MI, Piknova B, Park JW, Wylie LJ, Stoyanov Z, Vanhatalo A, Schechter AN, Jones AM (2022). Pharmacokinetics of Skeletal Muscle Nitrate Concentration Changes Following Dietary Nitrate Ingestion. Medicine & Science in Sports & Exercise, 54(9S), 651-651.
Tan R, Black M, Home J, Blackwell J, Clark I, Wylie L, Vanhatalo A, Jones AM (2022). Physiological and performance effects of dietary nitrate and N-acetylcysteine supplementation during prolonged heavy-intensity cycling.
J Sports Sci,
40(23), 2585-2594.
Abstract:
Physiological and performance effects of dietary nitrate and N-acetylcysteine supplementation during prolonged heavy-intensity cycling.
The purpose of this study was to investigate effects of concurrent and independent administration of dietary nitrate (NO3-), administered as NO3--rich beetroot juice (BR; ~12.4 mmol of NO3-), and N-acetylcysteine (NAC; 70 mg·kg-1) on physiological responses during prolonged exercise and subsequent high-intensity exercise tolerance. Sixteen recreationally active males supplemented with NO3--depleted beetroot juice (PL) or BR for 6 days and ingested an acute dose of NAC or maltodextrin (MAL) 1 h prior to performing 1 h of heavy-intensity cycling exercise immediately followed by a severe-intensity time-to-exhaustion (TTE) test in four conditions: 1) PL+MAL, 2) PL+NAC, 3) BR+MAL and 4) BR+NAC. Pre-exercise plasma [NO3-] and nitrite ([NO2-]) were elevated following BR+NAC and BR+MAL (both P
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Burnley M, Bearden SE, Jones AM (2022). Polarized Training is Not Optimal for Endurance Athletes.
Med Sci Sports Exerc,
54(6), 1032-1034.
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Burnley M, Bearden SE, Jones AM (2022). Polarized Training is Not Optimal for Endurance Athletes: Response to Foster and Colleagues.
MEDICINE & SCIENCE IN SPORTS & EXERCISE,
54(6), 1038-1040.
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Piknova B, Schechter AN, Park JW, Vanhatalo A, Jones AM (2022). Skeletal Muscle Nitrate as a Regulator of Systemic Nitric Oxide Homeostasis.
Exerc Sport Sci Rev,
50(1), 2-13.
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Skeletal Muscle Nitrate as a Regulator of Systemic Nitric Oxide Homeostasis.
Nonenzymatic nitric oxide (NO) generation via the reduction of nitrate and nitrite ions, along with remarkably high levels of nitrate ions in skeletal muscle, have been described recently. Skeletal muscle nitrate storage may be critical for maintenance of NO homeostasis in healthy aging, and nitrate supplementation may be useful for the treatment of specific pathophysiologies and for enhancing normal functions.
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Stoyanov Z, Piknova B, Schechter AN, Park JW, Wylie LJ, Kadach S, Black MI, Jones AM, Vanhatalo A (2022). The Influence of Prolonged Heavy-intensity Exercise on Human Skeletal Muscle Nitrate Concentration. Medicine & Science in Sports & Exercise, 54(9S), 650-651.
Sahin FB, Kafkas AS, Kafkas ME, Taskapan MC, Jones AM (2022). The effect of active vs passive recovery and use of compression garments following a single bout of muscle-damaging exercise.
ISOKINETICS AND EXERCISE SCIENCE,
30(2), 117-126.
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Kadach S, Piknova B, Black MI, Park JW, Wylie LJ, Stoyanov Z, Thomas SM, McMahon NF, Vanhatalo A, Schechter AN, et al (2022). Time course of human skeletal muscle nitrate and nitrite concentration changes following dietary nitrate ingestion.
Nitric Oxide,
121, 1-10.
Abstract:
Time course of human skeletal muscle nitrate and nitrite concentration changes following dietary nitrate ingestion.
Dietary nitrate (NO3-) ingestion can be beneficial for health and exercise performance. Recently, based on animal and limited human studies, a skeletal muscle NO3- reservoir has been suggested to be important in whole body nitric oxide (NO) homeostasis. The purpose of this study was to determine the time course of changes in human skeletal muscle NO3- concentration ([NO3-]) following the ingestion of dietary NO3-. Sixteen participants were allocated to either an experimental group (NIT: n = 11) which consumed a bolus of ∼1300 mg (12.8 mmol) potassium nitrate (KNO3), or a placebo group (PLA: n = 5) which consumed a bolus of potassium chloride (KCl). Biological samples (muscle (vastus lateralis), blood, saliva and urine) were collected shortly before NIT or PLA ingestion and at intervals over the course of the subsequent 24 h. At baseline, no differences were observed for muscle [NO3-] and [NO2-] between NIT and PLA (P > 0.05). In PLA, there were no changes in muscle [NO3-] or [NO2-] over time. In NIT, muscle [NO3-] was significantly elevated above baseline (54 ± 29 nmol/g) at 0.5 h, reached a peak at 3 h (181 ± 128 nmol/g), and was not different to baseline from 9 h onwards (P > 0.05). Muscle [NO2-] did not change significantly over time. Following ingestion of a bolus of dietary NO3-, skeletal muscle [NO3-] increases rapidly, reaches a peak at ∼3 h and subsequently declines towards baseline values. Following dietary NO3- ingestion, human m. vastus lateralis [NO3-] expressed a slightly delayed pharmacokinetic profile compared to plasma [NO3-].
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Jones AM, Vanhatalo A, Seals DR, Rossman MJ, Piknova B, Jonvik KL (2021). Dietary Nitrate and Nitric Oxide Metabolism: Mouth, Circulation, Skeletal Muscle, and Exercise Performance.
Med Sci Sports Exerc,
53(2), 280-294.
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Dietary Nitrate and Nitric Oxide Metabolism: Mouth, Circulation, Skeletal Muscle, and Exercise Performance.
Nitric oxide (NO) is a gaseous signaling molecule that plays an important role in myriad physiological processes, including the regulation of vascular tone, neurotransmission, mitochondrial respiration, and skeletal muscle contractile function. NO may be produced via the canonical NO synthase-catalyzed oxidation of l-arginine and also by the sequential reduction of nitrate to nitrite and then NO. The body's nitrate stores can be augmented by the ingestion of nitrate-rich foods (primarily green leafy vegetables). NO bioavailability is greatly enhanced by the activity of bacteria residing in the mouth, which reduce nitrate to nitrite, thereby increasing the concentration of circulating nitrite, which can be reduced further to NO in regions of low oxygen availability. Recent investigations have focused on promoting this nitrate-nitrite-NO pathway to positively affect indices of cardiovascular health and exercise tolerance. It has been reported that dietary nitrate supplementation with beetroot juice lowers blood pressure in hypertensive patients, and sodium nitrite supplementation improves vascular endothelial function and reduces the stiffening of large elastic arteries in older humans. Nitrate supplementation has also been shown to enhance skeletal muscle function and to improve exercise performance in some circumstances. Recently, it has been established that nitrate concentration in skeletal muscle is much higher than that in blood and that muscle nitrate stores are exquisitely sensitive to dietary nitrate supplementation and deprivation. In this review, we consider the possibility that nitrate represents an essential storage form of NO and discuss the integrated function of the oral microbiome, circulation, and skeletal muscle in nitrate-nitrite-NO metabolism, as well as the practical relevance for health and performance.
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Yilmaz K, Burnley M, Böcker J, Müller K, Jones AM, Rittweger J (2021). Influence of simulated hypogravity on oxygen uptake during treadmill running.
Physiol Rep,
9(9).
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Influence of simulated hypogravity on oxygen uptake during treadmill running.
Prolonged exposure to microgravity during spaceflights leads to severe deterioration in the physical performance of astronauts. To understand the effectiveness of existing in-flight daily countermeasures and to plan exercise onboard the International Space Station, we compared supine treadmill running to traditional upright treadmill running on earth. Specifically, we assessed the cardiorespiratory responses to conventional upright running to the responses to supine treadmill running under 0.3 g, 0.6 g, and 1 g of body weight in younger (20-30 years, n = 14, 8 females) and older healthy adults (50-60 years, n = 12, 6 females). Maximal cardiorespiratory capacity was additionally evaluated by performing an incremental running protocol on each treadmill. Maximum speed was greater for 0.3 g and 0.6 g in supine than for upright running (18.5 km/h (1.1) and 15.9 (3.1) vs 13.2 (2.4) p
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Kirby BS, Winn BJ, Wilkins BW, Jones AM (2021). Interaction of exercise bioenergetics with pacing behavior predicts track distance running performance.
J Appl Physiol (1985),
131(5), 1532-1542.
Abstract:
Interaction of exercise bioenergetics with pacing behavior predicts track distance running performance.
The best possible finishing time for a runner competing in distance track events can be estimated from their critical speed (CS) and the finite amount of energy that can be expended above CS (D´). During tactical races with variable pacing, the runner with the "best" combination of CS and D´ and, therefore, the fastest estimated finishing time prior to the race, does not always win. We hypothesized that final race finishing positions depend on the relationships between the pacing strategies used, the athletes' initial CS, and their instantaneous D´ (i.e. D´ balance) as the race unfolds. Using publicly available data from the 2017 International Association of Athletics Federations (IAAF) World Championships men's 5,000-m and 10,000-m races, race speed, CS, and D´ balance were calculated. The correlation between D´ balance and actual finishing positions was nonsignificant using start-line values but improved to R2 > 0.90 as both races progressed. The D´ balance with 400 m remaining was strongly associated with both final 400-m split time and proximity to the winner. Athletes who exhausted their D´ were unable to hold pace with the leaders, whereas a high D´ remaining enabled a fast final 400 m and a high finishing position. The D´ balance model was able to accurately predict finishing positions in both a "slow" 5,000-m and a "fast" 10,000-m race. These results indicate that although CS and D´ can characterize an athlete's performance capabilities prior to the start, the pacing strategy that optimizes D´ utilization significantly impacts the final race outcome.NEW & NOTEWORTHY We show that the interaction between exercise bioenergetics and real-time pacing strategy predicts track distance running performance. Critical speed (CS) and the finite energy expended above CS (D´) can characterize an athlete's capabilities prior to the race start, but the pacing strategy that optimizes D´ utilization ultimately impacts whether a runner is in contention to win and whether a runner will have a fast final 400 m. Accordingly, D´ balance predicts final race finishing order.
Abstract.
Author URL.
Burke LM, Hall R, Heikura IA, Ross ML, Tee N, Kent GL, Whitfield J, Forbes SF, Sharma AP, Jones AM, et al (2021). Neither beetroot juice supplementation nor increased carbohydrate oxidation enhance economy of prolonged exercise in elite race walkers.
Nutrients,
13(8).
Abstract:
Neither beetroot juice supplementation nor increased carbohydrate oxidation enhance economy of prolonged exercise in elite race walkers
Given the importance of exercise economy to endurance performance, we implemented two strategies purported to reduce the oxygen cost of exercise within a 4 week training camp in 21 elite male race walkers. Fourteen athletes undertook a crossover investigation with beetroot juice (BRJ) or placebo (PLA) [2 d preload, 2 h pre-exercise + 35 min during exercise] during a 26 km race walking at speeds simulating competitive events. Separately, 19 athletes undertook a parallel group investigation of a multi-pronged strategy (MAX; n = 9) involving chronic (2 w high carbohydrate [CHO] diet + gut training) and acute (CHO loading + 90 g/h CHO during exercise) strategies to promote endogenous and exogenous CHO availability, compared with strategies reflecting lower ranges of current guidelines (CON; n = 10). There were no differences between BRJ and PLA trials for rates of CHO (p = 0.203) or fat (p = 0.818) oxidation or oxygen consumption (p = 0.090). Compared with CON, MAX was associated with higher rates of CHO oxidation during exercise, with increased exogenous CHO use (CON; peak = ~0.45 g/min; MAX: peak = ~1.45 g/min, p < 0.001). High rates of exogenous CHO use were achieved prior to gut training, without further improvement, suggesting that elite athletes already optimise intestinal CHO absorption via habitual practices. No differences in exercise economy were detected despite small differences in substrate use. Future studies should investigate the impact of these strategies on sub-elite athletes’ economy as well as the performance effects in elite groups.
Abstract.
Vanhatalo A, L'Heureux JE, Kelly J, Blackwell JR, Wylie LJ, Fulford J, Winyard PG, Williams DW, van der Giezen M, Jones AM, et al (2021). Network analysis of nitrate-sensitive oral microbiome reveals interactions with cognitive function and cardiovascular health across dietary interventions. Redox Biology, 41, 101933-101933.
Nyberg M, Christensen PM, Blackwell JR, Hostrup M, Jones AM, Bangsbo J (2021). Nitrate-rich beetroot juice ingestion reduces skeletal muscle O2 uptake and blood flow during exercise in sedentary men.
J Physiol,
599(23), 5203-5214.
Abstract:
Nitrate-rich beetroot juice ingestion reduces skeletal muscle O2 uptake and blood flow during exercise in sedentary men.
Dietary nitrate supplementation has been shown to reduce pulmonary O2 uptake during submaximal exercise and enhance exercise performance. However, the effects of nitrate supplementation on local metabolic and haemodynamic regulation in contracting human skeletal muscle remain unclear. To address this, eight healthy young male sedentary subjects were assigned in a randomized, double-blind, crossover design to receive nitrate-rich beetroot juice (NO3, 9 mmol) and placebo (PLA) 2.5 h prior to the completion of a double-step knee-extensor exercise protocol that included a transition from unloaded to moderate-intensity exercise (MOD) followed immediately by a transition to intense exercise (HIGH). Compared with PLA, NO3 increased plasma levels of nitrate and nitrite. During MOD, leg V̇O2 and leg blood flow (LBF) were reduced to a similar extent (∼9%-15%) in NO3. During HIGH, leg V̇O2 was reduced by ∼6%-10% and LBF by ∼5%-9% (did not reach significance) in NO3. Leg V̇O2 kinetics was markedly faster in the transition from passive to MOD compared with the transition from MOD to HIGH both in NO3 and PLA with no difference between PLA and NO3. In NO3, a reduction in nitrate and nitrite concentration was detected between arterial and venous samples. No difference in the time to exhaustion was observed between conditions. In conclusion, elevation of plasma nitrate and nitrate reduces leg skeletal muscle V̇O2 and blood flow during exercise. However, nitrate supplementation does not enhance muscle V̇O2 kinetics during exercise, nor does it improve time to exhaustion when exercising with a small muscle mass. KEY POINTS: Dietary nitrate supplementation has been shown to reduce systemic O2 uptake during exercise and improve exercise performance. The effects of nitrate supplementation on local metabolism and blood flow regulation in contracting human skeletal muscle remain unclear. By using leg exercise engaging a small muscle mass, we show that O2 uptake and blood flow are similarly reduced in contracting skeletal muscle of humans during exercise. Despite slower V̇O2 kinetics in the transition from moderate to intense exercise, no effects of nitrate supplementation were observed for V̇O2 kinetics and time to exhaustion. Nitrate and nitrite concentrations are reduced across the exercising leg, suggesting that these ions are extracted from the arterial blood by contracting skeletal muscle.
Abstract.
Author URL.
Jones AM, Kirby BS, Clark IE, Rice HM, Fulkerson E, Wylie LJ, Wilkerson DP, Vanhatalo A, Wilkins BW (2021). Physiological demands of running at 2-hour marathon race pace.
J Appl Physiol (1985),
130(2), 369-379.
Abstract:
Physiological demands of running at 2-hour marathon race pace.
The requirements of running a 2-h marathon have been extensively debated but the actual physiological demands of running at ∼21.1 km/h have never been reported. We therefore conducted laboratory-based physiological evaluations and measured running economy (O2 cost) while running outdoors at ∼21.1 km/h, in world-class distance runners as part of Nike's "Breaking 2" marathon project. On separate days, 16 world-class male distance runners (age, 29 ± 4 yr; height, 1.72 ± 0.04 m; mass, 58.9 ± 3.3 kg) completed an incremental treadmill test for the assessment of V̇O2peak, O2 cost of submaximal running, lactate threshold and lactate turn-point, and a track test during which they ran continuously at 21.1 km/h. The laboratory-determined V̇O2peak was 71.0 ± 5.7 mL/kg/min with lactate threshold and lactate turn-point occurring at 18.9 ± 0.4 and 20.2 ± 0.6 km/h, corresponding to 83 ± 5% and 92 ± 3% V̇O2peak, respectively. Seven athletes were able to attain a steady-state V̇O2 when running outdoors at 21.1 km/h. The mean O2 cost for these athletes was 191 ± 19 mL/kg/km such that running at 21.1 km/h required an absolute V̇O2 of ∼4.0 L/min and represented 94 ± 3% V̇O2peak. We report novel data on the O2 cost of running outdoors at 21.1 km/h, which enables better modeling of possible marathon performances by elite athletes. Using the value for O2 cost measured in this study, a sub 2-h marathon would require a 59 kg runner to sustain a V̇O2 of approximately 4.0 L/min or 67 mL/kg/min.NEW & NOTEWORTHY We report the physiological characteristics and O2 cost of running overground at ∼21.1 km/h in a cohort of the world's best male distance runners. We provide new information on the absolute and relative O2 uptake required to run at 2-h marathon pace.
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Author URL.
Park JW, Thomas SM, Wylie LJ, Jones AM, Vanhatalo A, Schechter AN, Piknova B (2021). Preparation of Rat Skeletal Muscle Homogenates for Nitrate and Nitrite Measurements.
JOVE-JOURNAL OF VISUALIZED EXPERIMENTS(173).
Author URL.
Abu-Alghayth M, Vanhatalo A, Wylie LJ, McDonagh STJ, Thompson C, Kadach S, Kerr P, Smallwood MJ, Jones AM, Winyard PG, et al (2021). S-nitrosothiols, and other products of nitrate metabolism, are increased in multiple human blood compartments following ingestion of beetroot juice. Redox Biology, 43, 101974-101974.
Nixon RJ, Kranen SH, Vanhatalo A, Jones AM (2021). Steady-state [Formula: see text] above MLSS: evidence that critical speed better represents maximal metabolic steady state in well-trained runners.
Eur J Appl Physiol,
121(11), 3133-3144.
Abstract:
Steady-state [Formula: see text] above MLSS: evidence that critical speed better represents maximal metabolic steady state in well-trained runners.
The metabolic boundary separating the heavy-intensity and severe-intensity exercise domains is of scientific and practical interest but there is controversy concerning whether the maximal lactate steady state (MLSS) or critical power (synonymous with critical speed, CS) better represents this boundary. We measured the running speeds at MLSS and CS and investigated their ability to discriminate speeds at which [Formula: see text] was stable over time from speeds at which a steady-state [Formula: see text] could not be established. Ten well-trained male distance runners completed 9-12 constant-speed treadmill tests, including 3-5 runs of up to 30-min duration for the assessment of MLSS and at least 4 runs performed to the limit of tolerance for assessment of CS. The running speeds at CS and MLSS were significantly different (16.4 ± 1.3 vs. 15.2 ± 0.9 km/h, respectively; P
Abstract.
Author URL.
Senefeld JW, Haischer MH, Jones AM, Wiggins CC, Beilfuss R, Joyner MJ, Hunter SK (2021). Technological advances in elite marathon performance.
J Appl Physiol (1985),
130(6), 2002-2008.
Abstract:
Technological advances in elite marathon performance.
There is scientific and legal controversy about recent technological advances in performance running shoes that reduce the energetic cost of running and may provide a distinct competitive advantage. To better understand the potential performance-enhancing effects of technological advancements in marathon racing shoes, we examined the finishing times and racing shoes of the top 50 male and 50 female runners from the World Marathon Major series in the 2010s before and after the introduction of new Nike shoe models (4%, NEXT%, Alphafly, and other prototypes; herein referred to as "neoteric Nikes"). Data for racing shoes were available for 3,886 of the 3,900 performances recorded at the four annual marathons in Boston, London, Chicago, and New York. In full cohort analyses, marathon finishing times were 2.0% or 2.8 min (138.5 ± 8.1 min vs. 141.3 ± 7.4 min, P < 0.001) faster for male runners wearing neoteric Nikes compared with other shoes. For females, marathon finishing times were 2.6% or 4.3 min (159.1 ± 10.0 min vs. 163.4 ± 10.7 min, P < 0.001) faster for runners wearing neoteric Nikes. In a subset of within-runner changes in marathon performances (males, n = 138; females, n = 101), marathon finishing times improved by 0.8% or 1.2 min for males wearing neoteric Nikes relative to the most recent marathon in which other shoes were worn, and this performance-enhancing effect was greater among females who demonstrated 1.6% or 3.7 min improvement (P = 0.002). Our results demonstrate that marathon performances are substantially faster when world-class athletes, and particularly females, wear marathon racing shoes with technological advancements.NEW & NOTEWORTHY World-class athletes are substantively faster, wearing marathon racing shoes with technological advancements than other shoes when competing in the marathon. Our findings suggest that technological advances in footwear contributed to the recent improvements in marathon finishing times among elite runners and in record-setting marathon performances. This investigation highlights the importance of sports analytics and may have broad implications for the regulation of running footwear during competition.
Abstract.
Author URL.
Kaiser BW, Kruse KK, Gibson BM, Santisteban KJ, Larson EA, Wilkins BW, Jones AM, Halliwill JR, Minson CT (2021). The impact of elevated body core temperature on critical power as determined by a 3-min all-out test.
J Appl Physiol (1985),
131(5), 1543-1551.
Abstract:
The impact of elevated body core temperature on critical power as determined by a 3-min all-out test.
Critical power (CP) delineates the heavy and severe exercise intensity domains, and sustained work rates above CP result in an inexorable progression of oxygen uptake to a maximal value and, subsequently, the limit of exercise tolerance. The finite work capacity above CP, W', is defined by the curvature constant of the power-duration relationship. Heavy or severe exercise in a hot environment generates additional challenges related to the rise in body core temperature (Tc) that may impact CP and W'. The purpose of this study was to determine the effect of elevated Tc on CP and W'. CP and W' were estimated by end-test power (EP; mean of final 30 s) and work above end-test power (WEP), respectively, from 3-min "all-out" tests performed on a cycle ergometer. Volunteers (n = 8, 4 female) performed the 3-min tests during a familiarization visit and two experimental visits (thermoneutral vs. hot, randomized crossover design). Before experimental 3-min tests, the subjects were immersed in water (thermoneutral: 36°C for 30 min; hot: 40.5°C until Tc was ≥38.5°C). Mean Tc was significantly greater in the hot condition than in the thermoneutral condition (38.5 ± 0.0°C vs. 37.4 ± 0.2°C; means ± SD, P < 0.01). All 3-min tests were performed in an environmental chamber [thermoneutral: 18°C, 45% relative humidity (RH); hot: 38 °C, 40% RH]. EP was similar between thermoneutral (239 ± 57 W) and hot (234 ± 66 W; P = 0.55) conditions. WEP was similar between thermoneutral (10.9 ± 3.0 kJ) and hot conditions (9.3 ± 3.6; P = 0.19). These results suggest that elevated Tc has no significant impact on EP or WEP.NEW & NOTEWORTHY the parameters of the power-duration relationship (critical power and W') estimated by a 3-min all-out test were not altered by elevated body core temperature as compared with a thermoneutral condition.
Abstract.
Author URL.
Vanhatalo A, Blackwell J, Bailey SJ, Wylie LJ, Bond B, Nyberg M, Jones AM (2020). Dietary Nitrate Counteracts the Elevated Blood Pressure Response to Nitric Oxide Synthase Inhibition in Humans. Medicine & Science in Sports & Exercise, 52(7S), 232-233.
Connolly LJ, Scott S, Morencos CM, Fulford J, Jones AM, Knapp K, Krustrup P, Bailey SJ, Bowtell JL (2020). Impact of a novel home-based exercise intervention on health indicators in inactive premenopausal women: a 12-week randomised controlled trial.
Eur J Appl Physiol,
120(4), 771-782.
Abstract:
Impact of a novel home-based exercise intervention on health indicators in inactive premenopausal women: a 12-week randomised controlled trial.
PURPOSE: This study tested the hypothesis that a novel, audio-visual-directed, home-based exercise training intervention would be effective at improving cardiometabolic health and mental well-being in inactive premenopausal women. METHODS: Twenty-four inactive premenopausal women (39 ± 10 years) were randomly assigned to an audio-visual-directed exercise training group (DVD; n = 12) or control group (CON; n = 12). During the 12-week intervention period, the DVD group performed thrice-weekly training sessions of 15 min. Training sessions comprised varying-intensity movements involving multiplanar whole-body accelerations and decelerations (average heart rate (HR) = 76 ± 3% HRmax). CON continued their habitual lifestyle with no physical exercise. A series of health markers were assessed prior to and following the intervention. RESULTS: Following the DVD intervention, HDL cholesterol (pre: 1.83 ± 0.45, post: 1.94 ± 0.46 mmol/L) and mental well-being, assessed via the Warwick Edinburgh Mental Well-Being Scale, improved (P 0.05). There were no pre-post intervention changes in any of the outcome variables in the CON group (P > 0.05). CONCLUSION: the present study suggests that a novel, audio-visual-directed exercise training intervention, consisting of varied-intensity movements interspersed with spinal and lower limb mobility and balance tasks, can improve [HDL cholesterol] and mental well-being in premenopausal women. Therefore, home-based, audio-visual-directed exercise training (45 min/week) appears to be a useful tool to initiate physical activity and improve aspects of health in previously inactive premenopausal women.
Abstract.
Author URL.
Cocksedge SP, Breese BC, Morgan PT, Nogueira L, Thompson C, Wylie LJ, Jones AM, Bailey SJ (2020). Influence of muscle oxygenation and nitrate-rich beetroot juice supplementation on O2 uptake kinetics and exercise tolerance. Nitric Oxide, 99, 25-33.
Joyner MJ, Hunter SK, Lucia A, Jones AM (2020). Last Word on Viewpoint: Physiology and fast marathons.
J Appl Physiol (1985),
128(4), 1086-1087.
Author URL.
Joyner MJ, Hunter SK, Lucia A, Jones AM (2020). Physiology and fast marathons.
J Appl Physiol (1985),
128(4), 1065-1068.
Author URL.
Bailey SJ, Gandra PG, Jones AM, Hogan MC, Nogueira L (2020). Reply from Stephen J. Bailey, Paulo G. Gandra, Andrew M. Jones, Michael C. Hogan and Leonardo Nogueira.
J Physiol,
598(8), 1643-1644.
Author URL.
Ferguson SK, Redinius KM, Harral JW, Pak DI, Swindle DC, Hirai DM, Blackwell JR, Jones AM, Stenmark KR, Buehler PW, et al (2020). The effect of dietary nitrate supplementation on the speed-duration relationship in mice with sickle cell disease.
J Appl Physiol (1985),
129(3), 474-482.
Abstract:
The effect of dietary nitrate supplementation on the speed-duration relationship in mice with sickle cell disease.
Sickle cell disease (SCD) causes exercise intolerance likely due to impaired skeletal muscle function and low nitric oxide (NO) bioavailability. Dietary nitrate improves hemodynamic and metabolic control during exercise in humans and animals. The purpose of this investigation was to assess the impact of nitrate supplementation on exercise capacity as measured by the running speed to exercise duration relationship [critical speed (CS)]in mice with SCD. We tested the hypothesis that nitrate supplementation via beetroot juice (BR) would attenuate the exercise intolerance observed in mice with SCD. Ten wild-type (WT) and 18 Berkley sickle-cell mice (BERK) received water (WT: n = 10, BERK: n = 10) or nitrate-rich BR (BERK+BR: n = 8, nitrate dose 1 mmol/kg/day) for 5 days. Following the supplementation period, all mice performed 3-5 constant-speed treadmill tests that resulted in exhaustion within 1.5 to 20 min. Time to exhaustion vs. treadmill speed was fit to a hyperbolic model to determine CS. CS was significantly lower in BERK vs. WT and BERK+BR with no significant difference between WT and BERK+BR (WT: 36.6 ± 1.6, BERK: 23.8 ± 1.5, BERK+BR: 31.1 ± 2.1 m/min, P < 0.05). Exercise tolerance, measured via CS, was significantly lower in BERK mice relative to WT. However, BERK mice receiving 5 days of nitrate supplementation exhibited no difference in exercise tolerance when compared with WT. These results support the potential utility of a dietary nitrate intervention to improve functionality in SCD patients.NEW & NOTEWORTHY Sickle cell disease compromises muscle O2 delivery resulting in exercise intolerance. Dietary nitrate supplementation increases skeletal muscle blood flow during exercise and may improve exercise capacity in a mouse model of sickle cell disease. We investigated the effects of dietary nitrate supplementation on exercise tolerance in a mouse model of sickle cell disease using the treadmill speed-duration relationship (critical speed). Mice with sickle cell disease provided with a dietary nitrate supplement had a critical speed not significantly different from healthy wild-type mice.
Abstract.
Author URL.
Ashworth A, Vanhatalo A, Blackwell JR, Hayward GM, Jones AM (2020). Vegetables with High-Nitrate Content Significantly Increase Plasma Nitrate and Nitrite Concentrations but Do Not Significantly Reduce Systolic Blood Pressure in Young Healthy Men. European Journal of Nutrition & Food Safety, 67-82.
Morgan PT, Vanhatalo A, Bowtell JL, Jones AM, Bailey SJ (2019). Acetaminophen ingestion improves muscle activation and performance during a 3-min all-out cycling test.
Appl Physiol Nutr Metab,
44(4), 434-442.
Abstract:
Acetaminophen ingestion improves muscle activation and performance during a 3-min all-out cycling test.
Acute acetaminophen (ACT) ingestion has been shown to enhance cycling time-trial performance. The purpose of this study was to assess whether ACT ingestion enhances muscle activation and critical power (CP) during maximal cycling exercise. Sixteen active male participants completed two 3-min all-out tests against a fixed resistance on an electronically braked cycle ergometer 60 min after ingestion of 1 g of ACT or placebo (maltodextrin, PL). CP was estimated as the mean power output over the final 30 s of the test and W' (the curvature constant of the power-duration relationship) was estimated as the work done above CP. The femoral nerve was stimulated every 30 s to measure membrane excitability (M-wave) and surface electromyography (EMGRMS) was recorded continuously to infer muscle activation. Compared with PL, ACT ingestion increased CP (ACT: 297 ± 32 W vs. PL: 288 ± 31 W, P < 0.001) and total work done (ACT: 66.4 ± 6.5 kJ vs. PL: 65.4 ± 6.4 kJ, P = 0.03) without impacting W' (ACT: 13.1 ± 2.9 kJ vs. PL: 13.6 ± 2.4 kJ, P = 0.19) or the M-wave amplitude (P = 0.66) during the 3-min all-out cycling test. Normalised EMGRMS amplitude declined throughout the 3-min protocol in both PL and ACT conditions; however, the decline in EMGRMS amplitude was attenuated in the ACT condition, such that the EMGRMS amplitude was greater in ACT compared with PL over the last 60 s of the test (P = 0.04). These findings indicate that acute ACT ingestion might increase performance and CP during maximal cycling exercise by enhancing muscle activation.
Abstract.
Author URL.
Morgan PT, Vanhatalo A, Bowtell JL, Jones AM, Bailey SJ (2019). Acute ibuprofen ingestion does not attenuate fatigue during maximal intermittent knee extensor or all-out cycling exercise.
Appl Physiol Nutr Metab,
44(2), 208-215.
Abstract:
Acute ibuprofen ingestion does not attenuate fatigue during maximal intermittent knee extensor or all-out cycling exercise.
Recent research suggests that acute consumption of pharmacological analgesics can improve exercise performance, but the ergogenic potential of ibuprofen (IBP) administration is poorly understood. This study tested the hypothesis that IBP administration would enhance maximal exercise performance. In one study, 13 physically active males completed 60 × 3-s maximal voluntary contractions (MVCs) of the knee extensors interspersed with 2-s passive recovery periods, on 2 occasions, with the critical torque (CT) estimated as the mean torque over the last 12 contractions (part A). In another study, 16 active males completed two 3-min all-out tests against a fixed resistance on an electronically braked cycle ergometer, with the critical power estimated from the mean power output over the final 30 s of the test (part B). All tests were completed 60 min after ingestion of maltodextrin (placebo, PL) or 400 mg of IBP. Peripheral nerve stimulation was administered at regular intervals and electromyography was measured throughout. For part A, mean torque (IBP: 60% ± 13% of pre-exercise MVC; PL: 58% ± 14% of pre-exercise MVC) and CT (IBP: 41% ± 16% of pre-exercise MVC; PL: 40% ± 15% of pre-exercise MVC) were not different between conditions (P > 0.05). For part B, end-test power output (IBP: 292 ± 28 W; PL: 288 ± 31 W) and work done (IBP: 65.9 ± 5.9 kJ; PL: 65.4 ± 6.4 kJ) during the 3-min all-out cycling tests were not different between conditions (all P > 0.05). For both studies, neuromuscular fatigue declined at a similar rate in both conditions (P > 0.05). In conclusion, acute ingestion of 400 mg of IBP does not improve single-leg or maximal cycling performance in healthy humans.
Abstract.
Author URL.
Clark IE, Vanhatalo A, Thompson C, Wylie LJ, Bailey SJ, Kirby BS, Wilkins BW, Jones AM (2019). Changes in the power-duration relationship following prolonged exercise: estimation using conventional and all-out protocols and relationship with muscle glycogen.
Am J Physiol Regul Integr Comp Physiol,
317(1), R59-R67.
Abstract:
Changes in the power-duration relationship following prolonged exercise: estimation using conventional and all-out protocols and relationship with muscle glycogen.
It is not clear how the parameters of the power-duration relationship [critical power (CP) and W'] are influenced by the performance of prolonged endurance exercise. We used severe-intensity prediction trials (conventional protocol) and the 3-min all-out test (3MT) to measure CP and W' following 2 h of heavy-intensity cycling exercise and took muscle biopsies to investigate possible relationships to changes in muscle glycogen concentration ([glycogen]). Fourteen participants completed a rested 3MT to establish end-test power (Control-EP) and work done above EP (Control-WEP). Subsequently, on separate days, immediately following 2 h of heavy-intensity exercise, participants completed a 3MT to establish Fatigued-EP and Fatigued-WEP and three severe-intensity prediction trials to the limit of tolerance (Tlim) to establish Fatigued-CP and Fatigued-W'. A muscle biopsy was collected immediately before and after one of the 2-h exercise bouts. Fatigued-CP (256 ± 41 W) and Fatigued-EP (256 ± 52 W), and Fatigued-W' (15.3 ± 5.0 kJ) and Fatigued-WEP (14.6 ± 5.3 kJ), were not different (P > 0.05) but were ~11% and ~20% lower than Control-EP (287 ± 46 W) and Control-WEP (18.7 ± 4.7 kJ), respectively (P < 0.05). The change in muscle [glycogen] was not significantly correlated with the changes in either EP (r = 0.19) or WEP (r = 0.07). The power-duration relationship is adversely impacted by prolonged endurance exercise. The 3MT provides valid estimates of CP and W' following 2 h of heavy-intensity exercise, but the changes in these parameters are not primarily determined by changes in muscle [glycogen].
Abstract.
Author URL.
Burke LM, Jeukendrup AE, Jones AM, Mooses M (2019). Contemporary Nutrition Strategies to Optimize Performance in Distance Runners and Race Walkers.
Int J Sport Nutr Exerc Metab,
29(2), 117-129.
Abstract:
Contemporary Nutrition Strategies to Optimize Performance in Distance Runners and Race Walkers.
Distance events in Athletics include cross country, 10,000-m track race, half-marathon and marathon road races, and 20- and 50-km race walking events over different terrain and environmental conditions. Race times for elite performers span ∼26 min to >4 hr, with key factors for success being a high aerobic power, the ability to exercise at a large fraction of this power, and high running/walking economy. Nutrition-related contributors include body mass and anthropometry, capacity to use fuels, particularly carbohydrate (CHO) to produce adenosine triphosphate economically over the duration of the event, and maintenance of reasonable hydration status in the face of sweat losses induced by exercise intensity and the environment. Race nutrition strategies include CHO-rich eating in the hours per days prior to the event to store glycogen in amounts sufficient for event fuel needs, and in some cases, in-race consumption of CHO and fluid to offset event losses. Beneficial CHO intakes range from small amounts, including mouth rinsing, in the case of shorter events to high rates of intake (75-90 g/hr) in the longest races. A personalized and practiced race nutrition plan should balance the benefits of fluid and CHO consumed within practical opportunities, against the time, cost, and risk of gut discomfort. In hot environments, prerace hyperhydration or cooling strategies may provide a small but useful offset to the accrued thermal challenge and fluid deficit. Sports foods (drinks, gels, etc.) may assist in meeting training/race nutrition plans, with caffeine, and, perhaps nitrate being used as evidence-based performance supplements.
Abstract.
Author URL.
Morgan PT, Bailey SJ, Banks RA, Fulford J, Vanhatalo A, Jones AM (2019). Contralateral fatigue during severe-intensity single-leg exercise: influence of acute acetaminophen ingestion.
Am J Physiol Regul Integr Comp Physiol,
317(2), R346-R354.
Abstract:
Contralateral fatigue during severe-intensity single-leg exercise: influence of acute acetaminophen ingestion.
Exhaustive single-leg exercise has been suggested to reduce time to task failure (Tlim) during subsequent exercise in the contralateral leg by exacerbating central fatigue development. We investigated the influence of acetaminophen (ACT), an analgesic that may blunt central fatigue development, on Tlim during single-leg exercise completed with and without prior fatiguing exercise of the contralateral leg. Fourteen recreationally active men performed single-leg severe-intensity knee-extensor exercise to Tlim on the left (Leg1) and right (Leg2) legs without prior contralateral fatigue and on Leg2 immediately following Leg1 (Leg2-CONTRA). The tests were completed following ingestion of 1-g ACT or maltodextrin [placebo (PL)] capsules. Intramuscular phosphorus-containing metabolites and substrates and muscle activation were assessed using 31P-MRS and electromyography, respectively. Tlim was not different between Leg1ACT and Leg1PL conditions (402 ± 101 vs. 390 ± 106 s, P = 0.11). There was also no difference in Tlim between Leg2ACT-CONTRA and Leg2PL-CONTRA (324 ± 85 vs. 311 ± 92 s, P = 0.10), but Tlim was shorter in Leg2ACT-CONTRA and Leg2PL-CONTRA than in Leg2CON (385 ± 104 s, both P < 0.05). There were no differences in intramuscular phosphorus-containing metabolites and substrates or muscle activation between Leg1ACT and Leg1PL and between Leg2ACT-CONTRA and Leg2PL-CONTRA (all P > 0.05). These findings suggest that levels of metabolic perturbation and muscle activation at Tlim are not different during single-leg severe-intensity knee-extensor exercise completed with or without prior fatiguing exercise of the contralateral leg. Despite contralateral fatigue, ACT ingestion did not alter neuromuscular responses, muscle metabolites, or exercise performance.
Abstract.
Author URL.
Clark IE, Vanhatalo A, Thompson C, Joseph C, Black MI, Blackwell JR, Wylie LJ, Tan R, Bailey SJ, Wilkins BW, et al (2019). Dynamics of the power-duration relationship during prolonged endurance exercise and influence of carbohydrate ingestion.
J Appl Physiol (1985),
127(3), 726-736.
Abstract:
Dynamics of the power-duration relationship during prolonged endurance exercise and influence of carbohydrate ingestion.
We tested the hypotheses that the parameters of the power-duration relationship, estimated as the end-test power (EP) and work done above EP (WEP) during a 3-min all-out exercise test (3MT), would be reduced progressively after 40 min, 80 min, and 2 h of heavy-intensity cycling and that carbohydrate (CHO) ingestion would attenuate the reduction in EP and WEP. Sixteen participants completed a 3MT without prior exercise (control), immediately after 40 min, 80 min, and 2 h of heavy-intensity exercise while consuming a placebo beverage, and also after 2 h of heavy-intensity exercise while consuming a CHO supplement (60 g/h CHO). There was no difference in EP measured without prior exercise (260 ± 37 W) compared with EP after 40 min (268 ± 39 W) or 80 min (260 ± 40 W) of heavy-intensity exercise; however, after 2 h EP was 9% lower compared with control (236 ± 47 W; P < 0.05). There was no difference in WEP measured without prior exercise (17.9 ± 3.3 kJ) compared with after 40 min of heavy-intensity exercise (16.1 ± 3.3 kJ), but WEP was lower (P < 0.05) than control after 80 min (14.7 ± 2.9 kJ) and 2 h (13.8 ± 2.7 kJ). Compared with placebo, CHO ingestion negated the reduction of EP following 2 h of heavy-intensity exercise (254 ± 49 W) but had no effect on WEP (13.5 ± 3.4 kJ). These results reveal a different time course for the deterioration of EP and WEP during prolonged endurance exercise and indicate that EP is sensitive to CHO availability.NEW & NOTEWORTHY the parameters of the power-duration relationship [critical power (CP) and the curvature constant (W')] have typically been considered to be static. Here we report the time course for reductions in CP and W', as estimated with the 3-min all-out cycle test, during 2 h of heavy-intensity exercise. We also show that carbohydrate ingestion during exercise preserves CP, but not W', without altering muscle glycogen depletion. These results provide new mechanistic and practical insight into the power-duration curve and its relationship to exercise-related fatigue development.
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Author URL.
Wylie LJ, Park JW, Vanhatalo A, Kadach S, Black MI, Stoyanov Z, Schechter AN, Jones AM, Piknova B (2019). Human skeletal muscle nitrate store: influence of dietary nitrate supplementation and exercise.
J Physiol,
597(23), 5565-5576.
Abstract:
Human skeletal muscle nitrate store: influence of dietary nitrate supplementation and exercise.
KEY POINTS: Nitric oxide (NO), a potent vasodilator and a regulator of many physiological processes, is produced in mammals both enzymatically and by reduction of nitrite and nitrate ions. We have previously reported that, in rodents, skeletal muscle serves as a nitrate reservoir, with nitrate levels greatly exceeding those in blood or other internal organs, and with nitrate being reduced to NO during exercise. In the current study, we show that nitrate concentration is substantially greater in skeletal muscle than in blood and is elevated further by dietary nitrate ingestion in human volunteers. We also show that high-intensity exercise results in a reduction in the skeletal muscle nitrate store following supplementation, likely as a consequence of its reduction to nitrite and NO. We also report the presence of sialin, a nitrate transporter, and xanthine oxidoreductase in human skeletal muscle, indicating that muscle has the necessary apparatus for nitrate transport, storage and metabolism. ABSTRACT: Rodent skeletal muscle contains a large store of nitrate that can be augmented by the consumption of dietary nitrate. This muscle nitrate reservoir has been found to be an important source of nitrite and nitric oxide (NO) via its reduction by tissue xanthine oxidoreductase. To explore if this pathway is also active in human skeletal muscle during exercise, and if it is sensitive to local nitrate availability, we assessed exercise-induced changes in muscle nitrate and nitrite concentrations in young healthy humans, under baseline conditions and following dietary nitrate consumption. We found that baseline nitrate and nitrite concentrations were far higher in muscle than in plasma (∼4-fold and ∼29-fold, respectively), and that the consumption of a single bolus of dietary nitrate (12.8 mmol) significantly elevated nitrate concentration in both plasma (∼19-fold) and muscle (∼5-fold). Consistent with these observations, and with previous suggestions of active muscle nitrate transport, we present western blot data to show significant expression of the active nitrate/nitrite transporter sialin in human skeletal muscle. Furthermore, we report an exercise-induced reduction in human muscle nitrate concentration (by ∼39%), but only in the presence of an increased muscle nitrate store. Our results indicate that human skeletal muscle nitrate stores are sensitive to dietary nitrate intake and may contribute to NO generation during exercise. Together, these findings suggest that skeletal muscle plays an important role in the transport, storage and metabolism of nitrate in humans.
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Author URL.
Bailey SJ, Gandra PG, Jones AM, Hogan MC, Nogueira L (2019). Incubation with sodium nitrite attenuates fatigue development in intact single mouse fibres at physiological PO2.
J Physiol,
597(22), 5429-5443.
Abstract:
Incubation with sodium nitrite attenuates fatigue development in intact single mouse fibres at physiological PO2.
KEY POINTS: Dietary nitrate supplementation increases plasma nitrite concentration, which provides an oxygen-independent source of nitric oxide and can delay skeletal muscle fatigue. Nitrate supplementation has been shown to increase myofibre calcium release and force production in mouse skeletal muscle during contractions at a supra-physiological oxygen tension, but it is unclear whether nitrite exposure can delay fatigue development and improve myofibre calcium handling at a near-physiological oxygen tension. Single mouse muscle fibres acutely treated with nitrite had a lower force and cytosolic calcium concentration during single non-fatiguing contractions at a near-physiological oxygen tension. Nitrite treatment delayed fatigue development during repeated fatiguing isometric contractions at near-physiological, but not at supra-physiological, oxygen tension in combination with better maintenance of myofilament calcium sensitivity and sarcoplasmic reticulum calcium pumping. These findings improve understanding of the mechanisms by which increased skeletal muscle nitrite exposure might be ergogenic and imply that this is related to improved calcium handling. ABSTRACT: Dietary nitrate (NO3- ) supplementation, which increases plasma nitrite (NO2- ) concentration, has been reported to attenuate skeletal muscle fatigue development. Sarcoplasmic reticulum (SR) calcium (Ca2+ ) release is enhanced in isolated single skeletal muscle fibres following NO3- supplementation or NO2- incubation at a supra-physiological PO2 but it is unclear whether NO2- incubation can alter Ca2+ handling and fatigue development at a near-physiological PO2. We hypothesised that NO2- treatment would improve Ca2+ handling and delay fatigue at a physiological PO2 in intact single mouse skeletal muscle fibres. Each muscle fibre was perfused with Tyrode solution pre-equilibrated with either 20% ( PO2 ∼150 Torr) or 2% O2 ( PO2 = 15.6 Torr) in the absence and presence of 100 µM NaNO2. At supra-physiological PO2 (i.e. 20% O2 ), time to fatigue was lowered by 34% with NaNO2 (control: 257 ± 94 vs. NaNO2 : 159 ± 46 s, Cohen's d = 1.63, P
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Author URL.
Aboo Bakkar Z, Fulford J, Gates PE, Jackman SR, Jones AM, Bond B, Bowtell JL (2019). Montmorency cherry supplementation attenuates vascular dysfunction induced by prolonged forearm occlusion in overweight, middle-aged men.
J Appl Physiol (1985),
126(1), 246-254.
Abstract:
Montmorency cherry supplementation attenuates vascular dysfunction induced by prolonged forearm occlusion in overweight, middle-aged men.
Flavonoid supplementation improves brachial artery flow-mediated dilation (FMD), but it is not known whether flavonoids protect against vascular dysfunction induced by ischemia-reperfusion (IR) injury and associated respiratory burst. In a randomized, double-blind, placebo-controlled, crossover study, we investigated whether 4 wk supplementation with freeze-dried Montmorency cherry (MC) attenuated suppression of FMD after IR induced by prolonged forearm occlusion. Twelve physically inactive overweight, middle-aged men (52.8 ± 5.8 yr, BMI: 28.1 ± 5.3 kg/m2) consumed MC (235 mg/day anthocyanins) or placebo capsules for 4 wk, with supplementation blocks separated by 4 wk washout. Before and after each supplementation block, FMD responses and plasma nitrate and nitrite ([ NO2- ]) concentrations were measured at baseline and 15, 30, and 45 min after prolonged (20 min) forearm occlusion. FMD response was significantly depressed by the prolonged occlusion ( P < 0.001). After a 45-min reperfusion, FMD was restored to baseline levels after MC (ΔFMD presupplementation: -30.5 ± 8.4%, postsupplementation: -0.6 ± 9.5%) but not placebo supplementation (ΔFMD presupplementation: -11.6 ± 10.6, postsupplementation: -25.4 ± 4.0%; condition × supplement interaction: P = 0.038). Plasma [ NO2- ] decreased after prolonged occlusion but recovered faster after MC compared with placebo (Δ45 min to baseline; MC: presupplementation: -15.3 ± 9.6, postsupplementation: -6.2 ± 8.1; Placebo: presupplementation: -16.3 ± 5.9, postsupplementation: -27.7 ± 11.1 nmol/l; condition × supplement × time interaction: P = 0.033). Plasma peroxiredoxin concentration ([Prx2]) was significantly higher after MC (presupplementation: 22.8 ± 1.4, postsupplementation: 28.0 ± 2.4 ng/ml, P = 0.029) but not after placebo supplementation (presupplementation: 22.1 ± 2.2, postsupplementation: 23.7 ± 1.5 ng/ml). In conclusion, 4 wk MC supplementation enhanced recovery of endothelium-dependent vasodilatation after IR, in parallel with faster recovery of plasma [ NO2- ], suggesting NO dependency. These protective effects seem to be related to increased plasma [Prx2], presumably conferring protection against the respiratory burst during reperfusion. NEW & NOTEWORTHY This is the first study to demonstrate that 4 wk of Montmorency cherry powder supplementation exerted protective effects on endothelium-dependent vasodilation after transient ischemia-reperfusion injury in overweight, physically inactive, nonmedicated, hypertensive middle-aged men. These effects seem to be due to increased nitric oxide availability, as evidenced by higher plasma nitrite concentration and peak arterial diameter during the flow-mediated dilation measurement. This may be a consequence of increased concentration of peroxiredoxin and other antioxidant systems and, hence, reduced reactive oxygen species exposure.
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Author URL.
McDonagh STJ, Wylie LJ, Thompson C, Vanhatalo A, Jones AM (2019). Potential benefits of dietary nitrate ingestion in healthy and clinical populations: a brief review.
Eur J Sport Sci,
19(1), 15-29.
Abstract:
Potential benefits of dietary nitrate ingestion in healthy and clinical populations: a brief review.
This article provides an overview of the current literature relating to the efficacy of dietary nitrate (NO3-) ingestion in altering aspects of cardiovascular and metabolic health and exercise capacity in healthy and diseased individuals. The consumption of NO3--rich vegetables, such as spinach and beetroot, have been variously shown to promote nitric oxide bioavailability, reduce systemic blood pressure, enhance tissue blood flow, modulate muscle O2 utilisation and improve exercise tolerance both in normoxia and in hypoxia, as is commonly observed in a number of disease states. NO3- ingestion may, therefore, act as a natural means for augmenting performance and attenuating complications associated with limited O2 availability or transport, hypertension and the metabolic syndrome. Recent studies indicate that dietary NO3- might also augment intrinsic skeletal muscle contractility and improve the speed and power of muscle contraction. Moreover, several investigations suggest that NO3- supplementation may improve aspects of cognitive performance both at rest and during exercise. Collectively, these observations position NO3- as more than a putative ergogenic aid and suggest that increasing natural dietary NO3- intake may act as a prophylactic in countering the predations of senescence and certain cardiovascular-metabolic diseases.
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Author URL.
Jones AM, Burnley M, Black MI, Poole DC, Vanhatalo A (2019). Response to considerations regarding Maximal Lactate Steady State determination before redefining the gold-standard.
Physiol Rep,
7(22).
Abstract:
Response to considerations regarding Maximal Lactate Steady State determination before redefining the gold-standard.
We reinforce the key messages in our earlier review paper that critical power, rather than maximal lactate steady state, provides the better index for defining steady-state vs non-steady state physiological behaviour during exercise.
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Author URL.
Morgan PT, Black MI, Bailey SJ, Jones AM, Vanhatalo A (2019). Road cycle TT performance: Relationship to the power-duration model and association with FTP.
Journal of Sports Sciences,
37(8), 902-910.
Abstract:
Road cycle TT performance: Relationship to the power-duration model and association with FTP
Purpose: to determine the accuracy of critical power (CP) and Wʹ (the curvature constant of the power-duration relationship) derived from self-paced time-trial (TT) prediction trials using mobile power meters to predict 16.1-km road cycling TT performance. This study also aimed to assess the agreement between functional threshold power (FTP) and CP. Methods: Twelve competitive male cyclists completed an incremental test to exhaustion, a FTP test and 4–5 self-paced TT bouts on a stationary bike within the lab, and a 16.1 km road TT, using mobile power meters. Results: CP and Wʹ derived from the power-duration relationship closely predicted TT performance. The 16.1-km road TT completion time (26.7 ± 2.2 min) was not significantly different from and was significantly correlated with the predicted time-to-completion (27.5 ± 3.3 min, r = 0.89, P 0.05); however, the limits of agreement between CP and FTP were 30 to -36 W. Discussion: the findings of this study indicate that CP and Wʹ determined using mobile power meters during maximal, self-paced TT prediction trials can be used to accurately predict 16.1-km cycling performance, supporting the application of the CP and Wʹ for performance prediction. However, the limits of agreement were too large to consider FTP and CP interchangeable.
Abstract.
Jones AM, Burnley M, Black MI, Poole DC, Vanhatalo A (2019). The maximal metabolic steady state: redefining the 'gold standard'.
Physiol Rep,
7(10).
Abstract:
The maximal metabolic steady state: redefining the 'gold standard'.
The maximal lactate steady state (MLSS) and the critical power (CP) are two widely used indices of the highest oxidative metabolic rate that can be sustained during continuous exercise and are often considered to be synonymous. However, while perhaps having similarities in principle, methodological differences in the assessment of these parameters typically result in MLSS occurring at a somewhat lower power output or running speed and exercise at CP being sustainable for no more than approximately 20-30 min. This has led to the view that CP overestimates the 'actual' maximal metabolic steady state and that MLSS should be considered the 'gold standard' metric for the evaluation of endurance exercise capacity. In this article we will present evidence consistent with the contrary conclusion: i.e. that (1) as presently defined, MLSS naturally underestimates the actual maximal metabolic steady state; and (2) CP alone represents the boundary between discrete exercise intensity domains within which the dynamic cardiorespiratory and muscle metabolic responses to exercise differ profoundly. While both MLSS and CP may have relevance for athletic training and performance, we urge that the distinction between the two concepts/metrics be better appreciated and that comparisons between MLSS and CP, undertaken in the mistaken belief that they are theoretically synonymous, is discontinued. CP represents the genuine boundary separating exercise in which physiological homeostasis can be maintained from exercise in which it cannot, and should be considered the gold standard when the goal is to determine the maximal metabolic steady state.
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Clark IE, Goulding RP, DiMenna FJ, Bailey SJ, Jones MI, Fulford J, McDonagh STJ, Jones AM, Vanhatalo A (2019). Time-trial performance is not impaired in either competitive athletes or untrained individuals following a prolonged cognitive task.
Eur J Appl Physiol,
119(1), 149-161.
Abstract:
Time-trial performance is not impaired in either competitive athletes or untrained individuals following a prolonged cognitive task.
It has been reported that mental fatigue decreases exercise performance during high-intensity constant-work-rate exercise (CWR) and self-paced time trials (TT) in recreationally-trained individuals. The purpose of this study was to determine whether performance is impaired following a prolonged cognitive task in individuals trained for competitive sport. Ten trained competitive athletes (ATH) and ten untrained healthy men (UNT) completed a 6-min severe-intensity CWR followed by a 6-min cycling TT immediately following cognitive tasks designed to either perturb (Stroop colour-word task and N-back task; PCT) or maintain a neutral (documentary watching; CON) mental state. UNT had a higher heart rate (75 ± 9 v. 69 ± 7 bpm; P = 0.002) and a lower positive affect PANAS score (19.9 ± 7.5 v. 24.3 ± 4.6; P = 0.036) for PCT compared to CON. ATH showed no difference in heart rate, but had a higher negative affect score for PCT compared to CON (15.1 ± 3.7 v. 12.2 ± 2.7; P = 0.029). Pulmonary O2 uptake during CWR was not different between PCT and CON for ATH or UNT. Work completed during TT was not different between PCT and CON for ATH (PCT 103 ± 12 kJ; CON 102 ± 12 kJ; P > 0.05) or UNT (PCT 75 ± 11 kJ; CON 74 ± 12 kJ; P > 0.05). Compared to CON, during PCT, UNT showed unchanged psychological stress responses, whereas ATH demonstrated increased psychological stress responses. However, regardless of this distinction, exercise performance was not affected by PCT in either competitive athletes or untrained individuals.
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Author URL.
Morgan PT, Bowtell JL, Vanhatalo A, Jones AM, Bailey SJ (2018). Acute acetaminophen ingestion improves performance and muscle activation during maximal intermittent knee extensor exercise.
Eur J Appl Physiol,
118(3), 595-605.
Abstract:
Acute acetaminophen ingestion improves performance and muscle activation during maximal intermittent knee extensor exercise.
AIM: Acetaminophen is a commonly used medicine for pain relief and emerging evidence suggests that it may improve endurance exercise performance. This study investigated some of the physiological mechanisms by which acute acetaminophen ingestion might blunt muscle fatigue development. METHODS: Thirteen active males completed 60 × 3 s maximum voluntary contractions (MVC) of the knee extensors with each contraction separated by a 2 s passive recovery period. This protocol was completed 60 min after ingesting 1 g of maltodextrin (placebo) or 1 g of acetaminophen on two separate visits. Peripheral nerve stimulation was administered every 6th contraction for assessment of neuromuscular fatigue development, with the critical torque (CT), which reflects the maximal sustainable rate of oxidative metabolism, taken as the mean torque over the last 12 contractions. Surface electromyography was recorded continuously as a measure of muscle activation. RESULTS: Mean torque (61 ± 11 vs. 58 ± 14% pre-exercise MVC) and CT (44 ± 13 vs. 40 ± 15% pre-exercise MVC) were greater in the acetaminophen trial compared to placebo (both P 0.05). However, the decline in electromyography amplitude was attenuated in the acetaminophen trial, with electromyography amplitude being greater compared to placebo from 210 s onwards (P
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Tan R, Wylie LJ, Thompson C, Blackwell JR, Bailey SJ, Vanhatalo A, Jones AM (2018). Beetroot juice ingestion during prolonged moderate-intensity exercise attenuates progressive rise in O2 uptake.
Journal of Applied Physiology,
124(5), 1254-1263.
Abstract:
Beetroot juice ingestion during prolonged moderate-intensity exercise attenuates progressive rise in O2 uptake
Copyright © 2018 the American Physiological Society. Nitrate-rich beetroot juice (BR) supplementation has been shown to increase biomarkers of nitric oxide availability with implications for the physiological responses to exercise. We hypothesized that BR supplementation before and during prolonged moderate-intensity exercise would maintain an elevated plasma nitrite concentration ([NO2-]), attenuate the expected progressive increase in VO2over time, and improve performance in a subsequent time trial (TT). In a double-blind, randomized, crossover design, 12 men completed 2 h of moderate-intensity cycle exercise followed by a 100-kJ TT in three conditions: 1) BR before and 1 h into exercise (BR + BR); 2) BR before and placebo (PL) 1 h into exercise (BR + PL); and 3) PL before and 1 h into exercise (PL + PL). During the 2-h moderate-intensity exercise bout, plasma [NO2+] declined by ∼17% in BR + PL but increased by ∼8% in BR + BR such that, at 2 h, plasma [NO2-] was greater in BR + BR than both BR + PL and PL + PL (P < 0.05).VO2was not different among conditions over the first 90 min of exercise but was lower at 120 min in BR + BR (1.73 ± 0.24 l/min) compared with BR + PL (1.80 ± 0.21 l/min; P = 0.08) and PL + PL (1.83 ± 0.27 l/min; P < 0.01). The decline in muscle glycogen concentration over the 2-h exercise bout was attenuated in BR + BR (∼28% decline) compared with BR + PL (∼44% decline) and PL + PL (∼44% decline; n = 9, P < 0.05). TT performance was not different among conditions (P > 0.05). BR supplementation before and during prolonged moderate-intensity exercise attenuated the progressive rise in VO2over time and appeared to reduce muscle glycogen depletion but did not enhance subsequent TT performance. NEW & NOTEWORTHY We show for the first time that ingestion of nitrate during exercise preserves elevated plasma [nitrite] and negates the progressive rise in O2uptake during prolonged moderateintensity exercise.
Abstract.
Poole DC, Jones AM (2018). COMMENTARY ON VIEWPOINT: (V) over doto(2peak) IS AN ACCEPTABLE ESTIMATE OF CARDIORESPIRATORY FITNESS BUT NOT (V) over doto(2max).
JOURNAL OF APPLIED PHYSIOLOGY,
125(1), 238-238.
Author URL.
Azevedo P, Bhammar DM, Babb TG, Bowen S, Witte KK, Rossiter HB, Brugniaux JV, Perry BD, de Lucas DR, Turnes T, et al (2018). Commentaries on Viewpoint: <(V)over dot>(O2peak) is an acceptable estimate of cardiorespiratory fitness but not <(V)over dot>(O2max) (vol 125, pg 233, 2018).
JOURNAL OF APPLIED PHYSIOLOGY,
125(3), 970-970.
Author URL.
Azevedo P, Bhammar DM, Babb TG, Bowen TS, Witte KK, Rossiter HB, Brugniaux JV, Perry BD, Dantas de Lucas R, Turnes T, et al (2018). Commentaries on Viewpoint: V̇o2peak is an acceptable estimate of cardiorespiratory fitness but not V̇o2max.
J Appl Physiol (1985),
125(1), 233-240.
Author URL.
Jones AM, Thompson C, Wylie LJ, Vanhatalo A (2018). Dietary Nitrate and Physical Performance.
Annu Rev Nutr,
38, 303-328.
Abstract:
Dietary Nitrate and Physical Performance.
Nitric oxide (NO) plays a plethora of important roles in the human body. Insufficient production of NO (for example, during older age and in various disease conditions) can adversely impact health and physical performance. In addition to its endogenous production through the oxidation of l-arginine, NO can be formed nonenzymatically via the reduction of nitrate and nitrite, and the storage of these anions can be augmented by the consumption of nitrate-rich foodstuffs such as green leafy vegetables. Recent studies indicate that dietary nitrate supplementation, administered most commonly in the form of beetroot juice, can ( a) improve muscle efficiency by reducing the O2 cost of submaximal exercise and thereby improve endurance exercise performance and ( b) enhance skeletal muscle contractile function and thereby improve muscle power and sprint exercise performance. This review describes the physiological mechanisms potentially responsible for these effects, outlines the circumstances in which ergogenic effects are most likely to be evident, and discusses the effects of dietary nitrate supplementation on physical performance in a range of human populations.
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Thompson C, Vanhatalo A, Kadach S, Wylie LJ, Fulford J, Ferguson SK, Blackwell JR, Bailey SJ, Jones AM (2018). Discrete physiological effects of beetroot juice and potassium nitrate supplementation following 4-wk sprint interval training.
Journal of Applied Physiology,
124(6), 1519-1528.
Abstract:
Discrete physiological effects of beetroot juice and potassium nitrate supplementation following 4-wk sprint interval training
Copyright © 2018 American Physiological Society. All rights reserved. The physiological and exercise performance adaptations to sprint interval training (SIT) may be modified by dietary nitrate (NO3) supplementation. However, it is possible that different types of NO3supplementation evoke divergent physiological and performance adaptations to SIT. The purpose of this study was to compare the effects of 4-wk SIT with and without concurrent dietary NO3supplementation administered as either NO3-rich beetroot juice (BR) or potassium NO3(KNO3). Thirty recreationally active subjects completed a battery of exercise tests before and after a 4-wk intervention in which they were allocated to one of three groups: 1) SIT undertaken without dietary NO3supplementation (SIT); 2) SIT accompanied by concurrent BR supplementation (SIT BR); or 3) SIT accompanied by concurrent KNO3 supplementation (SIT KNO3). During severe-intensity exercise, V O2peak and time to task failure were improved to a greater extent with SIT +BR than SIT and SIT KNO3 (P 0.05). There was also a greater reduction in the accumulation of muscle lactate at 3 min of severe-intensity exercise in SIT BR compared with SIT KNO3 (P
Abstract.
Breese B, Poole D, Okushima D, Bailey S, Jones A, Kondo N, Amano T, Koga S (2018). Effect of Inorganic Nitrate Supplementation on O2 Uptake and Quadriceps Deoxygenation During the Onset and Offset of Exercise. Medicine & Science in Sports & Exercise, 50(5S).
Keane KM, Bailey SJ, Vanhatalo A, Jones AM, Howatson G (2018). Effects of Montmorency Tart Cherry (L. Prunus Cerasus) Consumption on Nitric Oxide Biomarkers and Exercise Performance. Medicine & Science in Sports & Exercise, 50(5S).
Clark IE, Vanhatalo A, Bailey SJ, Wylie LJ, Kirby BS, Wilkins BW, Jones AM (2018). Effects of Two Hours of Heavy-Intensity Exercise on the Power-Duration Relationship.
Med Sci Sports Exerc,
50(8), 1658-1668.
Abstract:
Effects of Two Hours of Heavy-Intensity Exercise on the Power-Duration Relationship.
INTRODUCTION: Changes in the parameters of the power-time relationship (critical power (CP) and W') during endurance exercise would have important implications for performance. We tested the hypotheses that CP and W', estimated using the end-test power (EP) and the work done above EP (WEP), respectively, during a the 3-min all-out test (3MT), can be reliably determined, and would be lower, after completing 2 h of heavy-intensity exercise. METHODS: in study 1, six cyclists completed a 3MT immediately after 2 h of heavy-intensity exercise on two occasions to establish the reliability of EP and WEP. In study 2, nine cyclists completed a control 3MT, and a fatigued 3MT and constant power output tests to 30 min or the limit of tolerance (Tlim) below and above F-EP after 2 h of heavy-intensity exercise. RESULTS: in study 1, EP (273 ± 52 vs 276 ± 58 W) and WEP (12.4 ± 4.3 vs 12.8 ± 4.3 kJ) after 2 h of heavy-intensity exercise were not different (P > 0.05) and were highly correlated (r = 0.99; P < 0.001). In study 2, both EP (F-EP: 282 ± 52 vs C-EP: 306 ± 56 W; P < 0.01) and WEP (F-WEP: 14.7 ± 4.9 vs C-WEP: 18.3 ± 4.1 kJ; P < 0.05) were lower after 2-h heavy-intensity exercise. However, maximum O2 uptake was not achieved during exercise >F-EP and Tlim was shorter than 30 min during exercise
Abstract.
Author URL.
Keane KM, Bailey SJ, Vanhatalo A, Jones AM, Howatson G (2018). Effects of montmorency tart cherry (L. Prunus Cerasus) consumption on nitric oxide biomarkers and exercise performance.
Scand J Med Sci Sports,
28(7), 1746-1756.
Abstract:
Effects of montmorency tart cherry (L. Prunus Cerasus) consumption on nitric oxide biomarkers and exercise performance.
The purpose of this study was to investigate the effects of Montmorency tart cherry juice (MC) on nitric oxide (NO) biomarkers, vascular function, and exercise performance. In a randomized, double-blind, placebo (PLA)-controlled, crossover study, 10 trained cyclists (mean ± SD; V˙O2peak 59.0 ± 7.0 mL/kg/min) acutely ingested 30 mL of either MC or PLA following dietary restrictions of polyphenol-rich compounds and completed 6-minutes moderate- and severe-intensity cycling bouts 1.5 hour post-ingestion on 2 occasions for each experimental condition. The severe-intensity cycling test was continued to exhaustion on 1 occasion and immediately followed by a 60-seconds all-out sprint on the other occasion. Blood pressure, pulse wave measures, tissue oxygenation index, and plasma nitrite concentration were assessed pre- and 1.5 hour post-ingestion. Time to exhaustion was not different between conditions (P > .05), but peak power over the first 20 seconds (363 ± 42 vs 330 ± 26 W) and total work completed during the 60-seconds all-out sprint (21 ± 3 vs 19 ± 3 kJ) were 10% higher in the MC trial compared to the PLA trial (P
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Author URL.
Rasica L, Porcelli S, Marzorati M, Salvadego D, Vezzoli A, Agosti F, De Col A, Tringali G, Jones AM, Sartorio A, et al (2018). Ergogenic effects of beetroot juice supplementation during severe-intensity exercise in obese adolescents.
Am J Physiol Regul Integr Comp Physiol,
315(3), R453-R460.
Abstract:
Ergogenic effects of beetroot juice supplementation during severe-intensity exercise in obese adolescents.
Previous studies showed a higher O2 cost of exercise, and therefore, a reduced exercise tolerance in patients with obesity during constant work rate (CWR) exercise compared with healthy subjects. Among the ergogenic effects of dietary nitrate ([Formula: see text]) supplementation in sedentary healthy subjects, a reduced O2 cost and enhanced exercise tolerance have often been demonstrated. The aim of this study was to evaluate the effects of beetroot juice (BR) supplementation, rich in [Formula: see text], on physiological variables associated with exercise tolerance in adolescents with obesity. In a double-blind, randomized crossover study, 10 adolescents with obesity (8 girls, 2 boys; age = 16 ± 1 yr; body mass index = 35.2 ± 5.0 kg/m2) were tested after 6 days of supplementation with BR (5 mmol [Formula: see text] per day) or placebo (PLA). Following each supplementation period, patients carried out two repetitions of 6-min moderate-intensity CWR exercise and one severe-intensity CWR exercise until exhaustion. Plasma [Formula: see text] concentration was significantly higher in BR versus PLA (108 ± 37 vs. 15 ± 5 μM, P < 0.0001). The O2 cost of moderate-intensity exercise was not different in BR versus PLA (13.3 ± 1.7 vs. 12.9 ± 1.1 ml·min-1·W-1, P = 0.517). During severe-intensity exercise, signs of a reduced amplitude of the O2 uptake slow component were observed in BR, in association with a significantly longer time to exhaustion (561 ± 198 s in BR vs. 457 ± 101 s in PLA, P = 0.0143). In obese adolescents, short-term dietary [Formula: see text] supplementation is effective in improving exercise tolerance during severe-intensity exercise. This may prove to be useful in counteracting early fatigue and reduced physical activity in this at-risk population.
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Author URL.
Brock K, Antonellis P, Black MI, DiMenna FJ, Vanhatalo A, Jones AM, Bailey SJ (2018). Improvement of Oxygen-Uptake Kinetics and Cycling Performance with Combined Prior Exercise and Fast Start.
Int J Sports Physiol Perform,
13(3), 305-312.
Abstract:
Improvement of Oxygen-Uptake Kinetics and Cycling Performance with Combined Prior Exercise and Fast Start.
PURPOSE: to investigate whether oxygen-uptake ([Formula: see text]) kinetics and simulated 4-km cycling performance are synergistically improved by prior "priming" exercise and an all-out starting strategy. METHODS: Nine men completed 4 target work trials (114 ± 17 kJ) to assess [Formula: see text] kinetics and cycling performance in a repeated-measures, crossover experimental design. Trials were initiated with either a 12-s all-out start or a self-selected start and preceded by prior severe-intensity (70%Δ) priming exercise or no priming exercise. RESULTS: the [Formula: see text] mean response time (MRT) was lower (indicative of faster [Formula: see text] kinetics) in the all-out primed condition (20 ± 6 s) than in the all-out unprimed (23 ± 6 s), self-paced-unprimed (42 ± 13 s), and self-paced-primed (42 ± 11 s) trials (P
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Author URL.
McDonagh STJ, Wylie LJ, Webster JMA, Vanhatalo A, Jones AM (2018). Influence of dietary nitrate food forms on nitrate metabolism and blood pressure in healthy normotensive adults.
Nitric Oxide,
72, 66-74.
Abstract:
Influence of dietary nitrate food forms on nitrate metabolism and blood pressure in healthy normotensive adults.
Inorganic nitrate (NO3-) supplementation has been shown to improve cardiovascular health indices in healthy adults. The purpose of this study was to investigate how the vehicle of NO3- administration can influence NO3- metabolism and the subsequent blood pressure response. Ten healthy males consumed an acute equimolar dose of NO3- (∼5.76 mmol) in the form of a concentrated beetroot juice drink (BR; 55 mL), a non-concentrated beetroot juice drink (BL; 456 mL) and a solid beetroot flapjack (BF; 60 g). A drink containing soluble beetroot crystals (BC; ∼1.40 mmol NO3-) and a control drink (CON; 70 mL deionised water) were also ingested. BP and plasma, salivary and urinary [NO3-] and [NO2-] were determined before and up to 24 h after ingestion. All NO3--rich vehicles elevated plasma, salivary and urinary nitric oxide metabolites compared with baseline and CON (P
Abstract.
Author URL.
Dewhurst-Trigg R, Yeates T, Blackwell JR, Thompson C, Linoby A, Morgan PT, Clarke I, Connolly LJ, Wylie LJ, Winyard PG, et al (2018). Lowering of blood pressure after nitrate-rich vegetable consumption is abolished with the co-ingestion of thiocyanate-rich vegetables in healthy normotensive males.
Nitric Oxide,
74, 39-46.
Abstract:
Lowering of blood pressure after nitrate-rich vegetable consumption is abolished with the co-ingestion of thiocyanate-rich vegetables in healthy normotensive males.
A diet rich in vegetables is known to provide cardioprotection. However, it is unclear how the consumption of different vegetables might interact to influence vascular health. This study tested the hypothesis that nitrate-rich vegetable consumption would lower systolic blood pressure but that this effect would be abolished when nitrate-rich and thiocyanate-rich vegetables are co-ingested. On four separate occasions, and in a randomized cross-over design, eleven healthy males reported to the laboratory and consumed a 750 mL vegetable smoothie that was either: low in nitrate (∼0.3 mmol) and thiocyanate (∼5 μmol), low in nitrate and high in thiocyanate (∼72 μmol), high in nitrate (∼4 mmol) and low in thiocyanate and high in nitrate and thiocyanate. Blood pressure as well as plasma and salivary [thiocyanate], [nitrate] and [nitrite] were assessed before and 3 h after smoothie consumption. Plasma [nitrate] and [nitrite] and salivary [nitrate] were not different after consuming the two high-nitrate smoothies, but salivary [nitrite] was higher after consuming the high-nitrate low-thiocyanate smoothie (1183 ± 625 μM) compared to the high-nitrate high-thiocyanate smoothie (941 ± 532 μM; P
Abstract.
Author URL.
Vanhatalo A, Blackwell JR, L'Heureux JE, Williams DW, Smith A, van der Giezen M, Winyard PG, Kelly J, Jones AM (2018). Nitrate-responsive oral microbiome modulates nitric oxide homeostasis and blood pressure in humans.
Free Radic Biol Med,
124, 21-30.
Abstract:
Nitrate-responsive oral microbiome modulates nitric oxide homeostasis and blood pressure in humans.
Imbalances in the oral microbial community have been associated with reduced cardiovascular and metabolic health. A possible mechanism linking the oral microbiota to health is the nitrate (NO3-)-nitrite (NO2-)-nitric oxide (NO) pathway, which relies on oral bacteria to reduce NO3- to NO2-. NO (generated from both NO2- and L-arginine) regulates vascular endothelial function and therefore blood pressure (BP). By sequencing bacterial 16S rRNA genes we examined the relationships between the oral microbiome and physiological indices of NO bioavailability and possible changes in these variables following 10 days of NO3- (12 mmol/d) and placebo supplementation in young (18-22 yrs) and old (70-79 yrs) normotensive humans (n = 18). NO3- supplementation altered the salivary microbiome compared to placebo by increasing the relative abundance of Proteobacteria (+225%) and decreasing the relative abundance of Bacteroidetes (-46%; P
Abstract.
Author URL.
Decroix L, Tonoli C, Lespagnol E, Balestra C, Descat A, Drittij-Reijnders MJ, Blackwell JR, Stahl W, Jones AM, Weseler AR, et al (2018). One-week cocoa flavanol intake increases prefrontal cortex oxygenation at rest and during moderate-intensity exercise in normoxia and hypoxia (vol 125, pg 8, 2018).
JOURNAL OF APPLIED PHYSIOLOGY,
125(2), 685-685.
Author URL.
Decroix L, Tonoli C, Lespagnol E, Balestra C, Descat A, Drittij-Reijnders MJ, Blackwell JR, Stahl W, Jones AM, Weseler AR, et al (2018). One-week cocoa flavanol intake increases prefrontal cortex oxygenation at rest and during moderate-intensity exercise in normoxia and hypoxia.
J Appl Physiol (1985),
125(1), 8-18.
Abstract:
One-week cocoa flavanol intake increases prefrontal cortex oxygenation at rest and during moderate-intensity exercise in normoxia and hypoxia.
During exercise in hypoxia, O2 delivery to brain and muscle is compromised, and oxidative stress is elicited. Cocoa flavanols (CF) have antioxidant capacities and can increase blood flow by stimulating endothelial function. We aimed to examine the effects of 7-day CF intake on oxidative stress, nitric oxide production, and tissue oxygenation in response to exercise in normobaric hypoxia (14.3% O2). In a randomized, double-blind, cross-over study, 14 well-trained male cyclists completed four trials: exercise in normoxia or hypoxia, after 7-day CF or placebo intake. Flow-mediated dilation (FMD) was measured before intake of the last dose CF or placebo. One hundred minutes later, 20-min steady-state (SS; 45% V̇o2max) and 20-min time trial (TT) (cycling) were performed. Blood samples were taken. Prefrontal and muscular oxygenation was assessed by near-infrared spectroscopy. At baseline, FMD was increased by CF. Hypoxia increased exercise-induced elevations in lipid peroxidation and antioxidant capacity. CF suppressed exercise-induced lipid peroxidation but did not influence antioxidant capacity. At rest and during SS, prefrontal and muscular oxygenation was decreased by hypoxia. CF elevated prefrontal oxygenation but did not impact muscular oxygenation. During TT, hypoxia accelerated the exercise-induced decrease in prefrontal oxygenation, but not in muscular oxygenation. During TT, CF did not alter prefrontal and muscular oxygenation. CF did not change plasma nitrite, nitrate, and arginine:citrulline. During high-intensity exercise, CF improved neither tissue oxygenation nor performance in well-trained athletes. At rest and during moderate-intensity exercise, CF reduced exercise-induced lipid peroxidation and partially restored the hypoxia-induced decline in prefrontal oxygenation. NEW & NOTEWORTHY for the first time, we showed that CF had beneficial effects on endothelial function at rest, as well as on prefrontal oxygenation at rest and during moderate-intensity exercise, both in normoxia and hypoxia. Moreover, we showed that CF intake inhibited oxidative stress during exhaustive exercise in hypoxia.
Abstract.
Author URL.
Burnley M, Jones AM (2018). Power-duration relationship: Physiology, fatigue, and the limits of human performance.
Eur J Sport Sci,
18(1), 1-12.
Abstract:
Power-duration relationship: Physiology, fatigue, and the limits of human performance.
The duration that exercise can be maintained decreases as the power requirements increase. In this review, we describe the power-duration (PD) relationship across the full range of attainable power outputs in humans. We show that a remarkably small range of power outputs is sustainable (power outputs below the critical power, CP). We also show that the origin of neuromuscular fatigue differs considerably depending on the exercise intensity domain in which exercise is performed. In the moderate domain (below the lactate threshold, LT), fatigue develops slowly and is predominantly of central origin (residing in the central nervous system). In the heavy domain (above LT but below CP), both central and peripheral (muscle) fatigue are observed. In this domain, fatigue is frequently correlated with the depletion of muscle glycogen. Severe-intensity exercise (above the CP) is associated with progressive derangements of muscle metabolic homeostasis and consequent peripheral fatigue. To counter these effects, muscle activity increases progressively, as does pulmonary oxygen uptake ([Formula: see text]), with task failure being associated with the attainment of [Formula: see text] max. Although the loss of homeostasis and thus fatigue develop more rapidly the higher the power output is above CP, the metabolic disturbance and the degree of peripheral fatigue reach similar values at task failure. We provide evidence that the failure to continue severe-intensity exercise is a physiological phenomenon involving multiple interacting mechanisms which indicate a mismatch between neuromuscular power demand and instantaneous power supply. Valid integrative models of fatigue must account for the PD relationship and its physiological basis.
Abstract.
Author URL.
Aboo Bakkar Z, Fulford J, Gates PE, Jackman SR, Jones AM, Bond B, Bowtell JL (2018). Prolonged forearm ischemia attenuates endothelium-dependent vasodilatation and plasma nitric oxide metabolites in overweight middle-aged men.
European Journal of Applied Physiology,
118(8), 1565-1572.
Abstract:
Prolonged forearm ischemia attenuates endothelium-dependent vasodilatation and plasma nitric oxide metabolites in overweight middle-aged men
Purpose: Repeated cycles of endothelial ischemia–reperfusion injury and the resulting respiratory burst contribute to the irreversible pathophysiology of vascular diseases, and yet, the effects of ischemia reperfusion on vascular function, oxidative stress, and nitric oxide (NO) bioavailability have not been assessed simultaneously. Therefore, this study sought to examine the effects of prolonged forearm occlusion and subsequent reperfusion on NO-dependent brachial artery endothelial function. Methods: Flow-mediated dilatation was measured at baseline and 15, 30, and 45 min after 20-min forearm occlusion in 14 healthy, but physically inactive middle-aged men (53.7 ± 1.2 years, BMI: 28.1 ± 0.1 kg m−2). Venous blood samples collected from the occluded arm were analyzed for NO metabolites and markers of oxidative stress. Results: FMD was significantly depressed after the prolonged occlusion compared to baseline, with a significant reduction 15-min post-occlusion (6.6 ± 0.7 to 2.9 ± 0.4%, p < 0.001); FMD remained depressed after 30 min (4.1 ± 0.6%, p = 0.001), but was not significantly different to baseline after 45-min recovery (5.4 ± 0.7%, p = 0.079). Plasma nitrate (main time effect: p = 0.015) and nitrite (main time effect: p = 0.034) concentrations were significantly reduced after prolonged occlusion. Plasma catalase activity was significantly elevated at 4- (p = 0.016) and 45-min (p = 0.001) post-occlusion, but plasma peroxiredoxin 2 and protein carbonyl content did not change. Conclusions: Prolonged forearm occlusion resulted in acute impairment of endothelium-dependent vasodilatation of the brachial artery for at least 30 min after reperfusion. We demonstrate that this vascular dysfunction is associated with oxidative stress and reduced NO bioavailability following reperfusion.
Abstract.
Edwards AM, Jones AM, Pyne DB (2018). Proposal to disregard athletics world records prior to 2005: a radical and misjudged initiative.
Br J Sports Med,
52(16), 1071-1072.
Author URL.
Black MI, Jones AM, Morgan PT, Bailey SJ, Fulford J, Vanhatalo A (2018). The effects of β-alanine supplementation on muscle pH and the power-duration relationship during high-intensity exercise.
Frontiers in Physiology,
9(FEB).
Abstract:
The effects of β-alanine supplementation on muscle pH and the power-duration relationship during high-intensity exercise
Purpose: to investigate the influence of β-alanine (BA) supplementation on muscle carnosine content, muscle pH and the power-duration relationship (i.e. critical power and W'). Methods: in a double-blind, randomized, placebo-controlled study, 20 recreationally-active males (22 ± 3 y, V°O2peak 3.73 ± 0.44 L·min-1) ingested either BA (6.4 g/d for 28 d) or placebo (PL) (6.4 g/d) for 28 d. Subjects completed an incremental test and two 3-min all-out tests separated by 1-min on a cycle ergometer pre- and post-supplementation. Muscle pH was assessed using 31P-magnetic resonance spectroscopy (MRS) during incremental (INC KEE) and intermittent knee-extension exercise (INT KEE). Muscle carnosine content was determined using 1H-MRS. Results: There were no differences in the change in muscle carnosine content from pre- to post-intervention (PL: 1 ± 16% vs. BA: -4 ± 25%) or in muscle pH during INC KEE or INT KEE (P > 0.05) between PL and BA, but blood pH (PL: -0.06 ± 0.10 vs. BA: 0.09 ± 0.13) during the incremental test was elevated post-supplementation in the BA group only (P < 0.05). The changes from pre- to post-supplementation in critical power (PL: -8 ± 18 W vs. BA: -6 ± 17 W) and W' (PL: 1.8 ± 3.3 kJ vs. BA: 1.5 ± 1.7 kJ) were not different between groups. No relationships were detected between muscle carnosine content and indices of exercise performance. Conclusions: BA supplementation had no significant effect on muscle carnosine content and no influence on intramuscular pH during incremental or high-intensity intermittent knee-extension exercise. The small increase in blood pH following BA supplementation was not sufficient to significantly alter the power-duration relationship or exercise performance.
Abstract.
Poole DC, Jones AM (2017). Clinical VO2peak is "part of the deal" Reply.
JOURNAL OF APPLIED PHYSIOLOGY,
122(5), 1371-1372.
Author URL.
Connolly LJ, Bailey SJ, Krustrup P, Fulford J, Smietanka C, Jones AM (2017). Effects of self-paced interval and continuous training on health markers in women.
Eur J Appl Physiol,
117(11), 2281-2293.
Abstract:
Effects of self-paced interval and continuous training on health markers in women.
PURPOSE: to compare the effects of self-paced high-intensity interval and continuous cycle training on health markers in premenopausal women. METHODS: Forty-five inactive females were randomised to a high-intensity interval training (HIIT; n = 15), continuous training (CT; n = 15) or an inactive control (CON; n = 15) group. HIIT performed 5 × 5 min sets comprising repetitions of 30-s low-, 20-s moderate- and 10-s high-intensity cycling with 2 min rest between sets. CT completed 50 min of continuous cycling. Training was completed self-paced, 3 times weekly for 12 weeks. RESULTS: Peak oxygen uptake (16 ± 8 and 21 ± 12%), resting heart rate (HR) (-5 ± 9 and -4 ± 7 bpm) and visual and verbal learning improved following HIIT and CT compared to CON (P
Abstract.
Author URL.
Stone MR, Thomas K, Wilkinson M, Stevenson E, St Clair Gibson A, Jones AM, Thompson KG (2017). Exploring the performance reserve: Effect of different magnitudes of power output deception on 4,000 m cycling time-trial performance.
PLoS One,
12(3).
Abstract:
Exploring the performance reserve: Effect of different magnitudes of power output deception on 4,000 m cycling time-trial performance.
PURPOSE: the aim of the present study was to investigate whether a magnitude of deception of 5% in power output would lead to a greater reduction in the amount of time taken for participants to complete a 4000 m cycling TT than a magnitude of deception of 2% in power output, which we have previously shown can lead to a small change in 4000 m cycling TT performance. METHODS: Ten trained male cyclists completed four, 4000 m cycling TTs. The first served as a habituation and the second as a baseline for future trials. During trials three and four participants raced against a pacer which was set, in a randomized order, at a mean power output equal to 2% (+2% TT) or 5% (+5% TT) higher than their baseline performance. However participants were misled into believing that the power output of the pacer was an accurate representation of their baseline performance on both occasions. Cardiorespiratory responses were recorded throughout each TT, and used to estimate energy contribution from aerobic and anaerobic metabolism. RESULTS: Participants were able to finish the +2% TT in a significantly shorter duration than at baseline (p = 0.01), with the difference in performance likely attributable to a greater anaerobic contribution to total power output (p = 0.06). There was no difference in performance between the +5% TT and +2% TT or baseline trials. CONCLUSIONS: Results suggest that a performance reserve is conserved, involving anaerobic energy contribution, which can be utilised given a belief that the exercise will be sustainable however there is an upper limit to how much deception can be tolerated. These findings have implications for performance enhancement in athletes and for our understanding of the nature of fatigue during high-intensity exercise.
Abstract.
Author URL.
Woodley C, Claridge R, Johnson N, Jones A (2017). Ignition and combustion of pyrotechnics at low pressures and at temperature extremes.
Defence Technology,
13(2), 119-126.
Abstract:
Ignition and combustion of pyrotechnics at low pressures and at temperature extremes
Rapid and effective ignition of pyrotechnic countermeasure decoy flares is vitally important to the safety of expensive military platforms such as aircraft. QinetiQ is conducting experimental and theoretical research into pyrotechnic countermeasure decoy flares. A key part of this work is the development and application of improved models to increase the understanding of the ignition processes occurring for these flares. These models have been implemented in a two-dimensional computational model and details are described in this paper. Previous work has conducted experiments and validated the computational model at ambient temperature and pressure. More recently the computational model has been validated at pressures down to that equivalent to 40,000 feet but at ambient temperature (∼290 K). This paper describes further experimental work in which the ignition delays of the priming material in inert countermeasure decoy flares were determined for pressures down to 40,000 feet and at temperature extremes of −40 °C and 100 °C. Also included in this paper is a comparison of the measured and predicted ignition delays at low pressures and temperature extremes. The agreement between the predicted and measured ignition delays is acceptable.
Abstract.
Thompson C, Wylie LJ, Blackwell JR, Fulford J, Black MI, Kelly J, McDonagh STJ, Carter J, Bailey SJ, Vanhatalo A, et al (2017). Influence of dietary nitrate supplementation on physiological and muscle metabolic adaptations to sprint interval training.
J Appl Physiol (1985),
122(3), 642-652.
Abstract:
Influence of dietary nitrate supplementation on physiological and muscle metabolic adaptations to sprint interval training.
We hypothesized that 4 wk of dietary nitrate supplementation would enhance exercise performance and muscle metabolic adaptations to sprint interval training (SIT). Thirty-six recreationally active subjects, matched on key variables at baseline, completed a series of exercise tests before and following a 4-wk period in which they were allocated to one of the following groups: 1) SIT and [Formula: see text]-depleted beetroot juice as a placebo (SIT+PL); 2) SIT and [Formula: see text]-rich beetroot juice (~13 mmol [Formula: see text]/day; SIT+BR); or 3) no training and [Formula: see text]-rich beetroot juice (NT+BR). During moderate-intensity exercise, pulmonary oxygen uptake was reduced by 4% following 4 wk of SIT+BR and NT+BR (P < 0.05) but not SIT+PL. The peak work rate attained during incremental exercise increased more in SIT+BR than in SIT+PL (P < 0.05) or NT+BR (P < 0.001). The reduction in muscle and blood [lactate] and the increase in muscle pH from preintervention to postintervention were greater at 3 min of severe-intensity exercise in SIT+BR compared with SIT+PL and NT+BR (P < 0.05). However, the change in severe-intensity exercise performance was not different between SIT+BR and SIT+PL (P > 0.05). The relative proportion of type IIx muscle fibers in the vastus lateralis muscle was reduced in SIT+BR only (P < 0.05). These findings suggest that BR supplementation may enhance some aspects of the physiological adaptations to SIT.NEW & NOTEWORTHY We investigated the influence of nitrate-rich and nitrate-depleted beetroot juice on the muscle metabolic and physiological adaptations to 4 wk of sprint interval training. Compared with placebo, dietary nitrate supplementation reduced the O2 cost of submaximal exercise, resulted in greater improvement in incremental (but not severe-intensity) exercise performance, and augmented some muscle metabolic adaptations to training. Nitrate supplementation may facilitate some of the physiological responses to sprint interval training.
Abstract.
Author URL.
Bailey SJ, Blackwell JR, Wylie LJ, Emery A, Taylor E, Winyard PG, Jones AM (2017). Influence of iodide ingestion on nitrate metabolism and blood pressure following short-term dietary nitrate supplementation in healthy normotensive adults.
Nitric Oxide,
63, 13-20.
Abstract:
Influence of iodide ingestion on nitrate metabolism and blood pressure following short-term dietary nitrate supplementation in healthy normotensive adults.
Uptake of inorganic nitrate (NO3-) into the salivary circulation is a rate-limiting step for dietary NO3- metabolism in mammals. It has been suggested that salivary NO3- uptake occurs in competition with inorganic iodide (I-). Therefore, this study tested the hypothesis that I- supplementation would interfere with NO3- metabolism and blunt blood pressure reductions after dietary NO3- supplementation. Nine healthy adults (4 male, mean ± SD, age 20 ± 1 yr) reported to the laboratory for initial baseline assessment (control) and following six day supplementation periods with 140 mL·day-1 NO3--rich beetroot juice (8.4 mmol NO3-·day-1) and 198 mg potassium gluconate·day-1 (nitrate), and 140 mL·day-1 NO3--rich beetroot juice and 450 μg potassium iodide·day-1 (nitrate + iodide) in a randomized, cross-over experiment. Salivary [I-] was higher in the nitrate + iodide compared to the control and NIT trials (P
Abstract.
Author URL.
Carden P, Bru B, Jones A, Dixon S (2017). Influence of rugby surface type and boot stud length on lower limb biomechanical variables associated with Achilles tendinopathy during Rugby Union specific movements. Footwear Science, 9, S132-S134.
Poole DC, Jones AM (2017). Measurement of the maximum oxygen uptake V̇o2max: V̇o2peak is no longer acceptable.
J Appl Physiol (1985),
122(4), 997-1002.
Abstract:
Measurement of the maximum oxygen uptake V̇o2max: V̇o2peak is no longer acceptable.
The maximum rate of O2 uptake (i.e. V̇o2max), as measured during large muscle mass exercise such as cycling or running, is widely considered to be the gold standard measurement of integrated cardiopulmonary-muscle oxidative function. The development of rapid-response gas analyzers, enabling measurement of breath-by-breath pulmonary gas exchange, has facilitated replacement of the discontinuous progressive maximal exercise test (that produced an unambiguous V̇o2-work rate plateau definitive for V̇o2max) with the rapidly incremented or ramp testing protocol. Although this is more suitable for clinical and experimental investigations and enables measurement of the gas exchange threshold, exercise efficiency, and V̇o2 kinetics, a V̇o2-work rate plateau is not an obligatory outcome. This shortcoming has led to investigators resorting to so-called secondary criteria such as respiratory exchange ratio, maximal heart rate, and/or maximal blood lactate concentration, the acceptable values of which may be selected arbitrarily and result in grossly inaccurate V̇o2max estimation. Whereas this may not be an overriding concern in young, healthy subjects with experience of performing exercise to volitional exhaustion, exercise test naïve subjects, patient populations, and less motivated subjects may stop exercising before their V̇o2max is reached. When V̇o2max is a or the criterion outcome of the investigation, this represents a major experimental design issue. This CORP presents the rationale for incorporation of a second, constant work rate test performed at ~110% of the work rate achieved on the initial ramp test to resolve the classic V̇o2-work rate plateau that is the unambiguous validation of V̇o2max the broad utility of this procedure has been established for children, adults of varying fitness, obese individuals, and patient populations.
Abstract.
Author URL.
Black MI, Jones AM, Blackwell JR, Bailey SJ, Wylie LJ, McDonagh STJ, Thompson C, Kelly J, Sumners P, Mileva KN, et al (2017). Muscle metabolic and neuromuscular determinants of fatigue during cycling in different exercise intensity domains.
J Appl Physiol (1985),
122(3), 446-459.
Abstract:
Muscle metabolic and neuromuscular determinants of fatigue during cycling in different exercise intensity domains.
Lactate or gas exchange threshold (GET) and critical power (CP) are closely associated with human exercise performance. We tested the hypothesis that the limit of tolerance (Tlim) during cycle exercise performed within the exercise intensity domains demarcated by GET and CP is linked to discrete muscle metabolic and neuromuscular responses. Eleven men performed a ramp incremental exercise test, 4-5 severe-intensity (SEV; >CP) constant-work-rate (CWR) tests until Tlim, a heavy-intensity (HVY; GET) CWR test until Tlim, and a moderate-intensity (MOD;. 0.05) muscle metabolic milieu (i.e. low pH and [PCr] and high [lactate]) was attained at Tlim (approximately 2-14 min) for all SEV exercise bouts. The muscle metabolic perturbation was greater at Tlim following SEV compared with HVY, and also following SEV and HVY compared with MOD (all P < 0.05). The normalized M-wave amplitude for the vastus lateralis (VL) muscle decreased to a similar extent following SEV (-38 ± 15%), HVY (-68 ± 24%), and MOD (-53 ± 29%), (P > 0.05). Neural drive to the VL increased during SEV (4 ± 4%; P < 0.05) but did not change during HVY or MOD (P > 0.05). During SEV and HVY, but not MOD, the rates of change in M-wave amplitude and neural drive were correlated with changes in muscle metabolic ([PCr], [lactate]) and blood ionic/acid-base status ([lactate], [K+]) (P < 0.05). The results of this study indicate that the metabolic and neuromuscular determinants of fatigue development differ according to the intensity domain in which the exercise is performed.NEW & NOTEWORTHY the gas exchange threshold and the critical power demarcate discrete exercise intensity domains. For the first time, we show that the limit of tolerance during whole-body exercise within these domains is characterized by distinct metabolic and neuromuscular responses. Fatigue development during exercise greater than critical power is associated with the attainment of consistent "limiting" values of muscle metabolites, whereas substrate availability and limitations to muscle activation may constrain performance at lower intensities.
Abstract.
Author URL.
Poole DC, Jones AM (2017). Reply to Cooper's letter in reference to: Measurement of the maximum oxygen uptake V̇o2max: V̇o2peak is no longer acceptable.
J Appl Physiol (1985),
123(2).
Author URL.
Poole DC, Jones AM (2017). Reply to Drs. Van Breda et al.
J Appl Physiol (1985),
122(5), 1371-1372.
Author URL.
Poole DC, Jones AM (2017). Reply to Pettitt and Jamnick's letter in reference to: Measurement of the maximum oxygen uptake V̇o2max: V̇o2peak is no longer acceptable.
J Appl Physiol (1985),
123(3).
Author URL.
Jones AM, Vanhatalo A (2017). The 'Critical Power' Concept: Applications to Sports Performance with a Focus on Intermittent High-Intensity Exercise.
Sports Med,
47(Suppl 1), 65-78.
Abstract:
The 'Critical Power' Concept: Applications to Sports Performance with a Focus on Intermittent High-Intensity Exercise.
The curvilinear relationship between power output and the time for which it can be sustained is a fundamental and well-known feature of high-intensity exercise performance. This relationship 'levels off' at a 'critical power' (CP) that separates power outputs that can be sustained with stable values of, for example, muscle phosphocreatine, blood lactate, and pulmonary oxygen uptake ([Formula: see text]), from power outputs where these variables change continuously with time until their respective minimum and maximum values are reached and exercise intolerance occurs. The amount of work that can be done during exercise above CP (the so-called W') is constant but may be utilized at different rates depending on the proximity of the exercise power output to CP. Traditionally, this two-parameter CP model has been employed to provide insights into physiological responses, fatigue mechanisms, and performance capacity during continuous constant power output exercise in discrete exercise intensity domains. However, many team sports (e.g. basketball, football, hockey, rugby) involve frequent changes in exercise intensity and, even in endurance sports (e.g. cycling, running), intensity may vary considerably with environmental/course conditions and pacing strategy. In recent years, the appeal of the CP concept has been broadened through its application to intermittent high-intensity exercise. With the assumptions that W' is utilized during work intervals above CP and reconstituted during recovery intervals below CP, it can be shown that performance during intermittent exercise is related to four factors: the intensity and duration of the work intervals and the intensity and duration of the recovery intervals. However, while the utilization of W' may be assumed to be linear, studies indicate that the reconstitution of W' may be curvilinear with kinetics that are highly variable between individuals. This has led to the development of a new CP model for intermittent exercise in which the balance of W' remaining ([Formula: see text]) may be calculated with greater accuracy. Field trials of athletes performing stochastic exercise indicate that this [Formula: see text] model can accurately predict the time at which W' tends to zero and exhaustion is imminent. The [Formula: see text] model potentially has important applications in the real-time monitoring of athlete fatigue progression in endurance and team sports, which may inform tactics and influence pacing strategy.
Abstract.
Author URL.
Breese BC, Poole DC, Okushima D, Bailey SJ, Jones AM, Kondo N, Amano T, Koga S (2017). The effect of dietary nitrate supplementation on the spatial heterogeneity of quadriceps deoxygenation during heavy-intensity cycling.
Physiol Rep,
5(14).
Abstract:
The effect of dietary nitrate supplementation on the spatial heterogeneity of quadriceps deoxygenation during heavy-intensity cycling.
This study investigated the influence of dietary inorganic nitrate (NO3-) supplementation on pulmonary O2 uptake (V˙O2) and muscle deoxyhemoglobin/myoglobin (i.e. deoxy [Hb + Mb]) kinetics during submaximal cycling exercise. In a randomized, placebo-controlled, cross-over study, eight healthy and physically active male subjects completed two step cycle tests at a work rate equivalent to 50% of the difference between the gas exchange threshold and peak V˙O2 over separate 4-day supplementation periods with NO3--rich (BR; providing 8.4 mmol NO3-∙day-1) and NO3--depleted (placebo; PLA) beetroot juice. Pulmonary V˙O2 was measured breath-by-breath and time-resolved near-infrared spectroscopy was utilized to quantify absolute deoxy [Hb + Mb] and total [Hb + Mb] within the rectus femoris, vastus lateralis, and vastus medialis There were no significant differences (P > 0.05) in the primary deoxy [Hb + Mb] mean response time or amplitude between the PLA and BR trials at each muscle site. BR significantly increased the mean (three-site) end-exercise deoxy [Hb + Mb] (PLA: 91 ± 9 vs. BR: 95 ± 12 μmol/L, P
Abstract.
Author URL.
Poole DC, Burnley M, Vanhatalo A, Rossiter HB, Jones AM (2016). Critical Power: an Important Fatigue Threshold in Exercise Physiology.
Med Sci Sports Exerc,
48(11), 2320-2334.
Abstract:
Critical Power: an Important Fatigue Threshold in Exercise Physiology.
: the hyperbolic form of the power-duration relationship is rigorous and highly conserved across species, forms of exercise, and individual muscles/muscle groups. For modalities such as cycling, the relationship resolves to two parameters, the asymptote for power (critical power [CP]) and the so-called W' (work doable above CP), which together predict the tolerable duration of exercise above CP. Crucially, the CP concept integrates sentinel physiological profiles-respiratory, metabolic, and contractile-within a coherent framework that has great scientific and practical utility. Rather than calibrating equivalent exercise intensities relative to metabolically distant parameters such as the lactate threshold or V˙O2max, setting the exercise intensity relative to CP unifies the profile of systemic and intramuscular responses and, if greater than CP, predicts the tolerable duration of exercise until W' is expended, V˙O2max is attained, and intolerance is manifested. CP may be regarded as a "fatigue threshold" in the sense that it separates exercise intensity domains within which the physiological responses to exercise can (CP) be stabilized. The CP concept therefore enables important insights into 1) the principal loci of fatigue development (central vs. peripheral) at different intensities of exercise and 2) mechanisms of cardiovascular and metabolic control and their modulation by factors such as O2 delivery. Practically, the CP concept has great potential application in optimizing athletic training programs and performance as well as improving the life quality for individuals enduring chronic disease.
Abstract.
Author URL.
McDonagh STJ, Vanhatalo A, Fulford J, Wylie LJ, Bailey SJ, Jones AM (2016). Dietary nitrate supplementation attenuates the reduction in exercise tolerance following blood donation.
Am J Physiol Heart Circ Physiol,
311(6), H1520-H1529.
Abstract:
Dietary nitrate supplementation attenuates the reduction in exercise tolerance following blood donation.
We tested the hypothesis that dietary nitrate (NO3-)-rich beetroot juice (BR) supplementation could partially offset deteriorations in O2 transport and utilization and exercise tolerance after blood donation. Twenty-two healthy volunteers performed moderate-intensity and ramp incremental cycle exercise tests prior to and following withdrawal of ∼450 ml of whole blood. Before donation, all subjects consumed seven 70-ml shots of NO3--depleted BR [placebo (PL)] in the 48 h preceding the exercise tests. During the 48 h after blood donation, subjects consumed seven shots of BR (each containing 6.2 mmol of NO3-, n = 11) or PL (n = 11) before repeating the exercise tests. Hemoglobin concentration and hematocrit were reduced by ∼8-9% following blood donation (P < 0.05), with no difference between the BR and PL groups. Steady-state O2 uptake during moderate-intensity exercise was ∼4% lower after than before donation in the BR group (P < 0.05) but was unchanged in the PL group. The ramp test peak power decreased from predonation (341 ± 70 and 331 ± 68 W in PL and BR, respectively) to postdonation (324 ± 69 and 322 ± 66 W in PL and BR, respectively) in both groups (P < 0.05). However, the decrement in performance was significantly less in the BR than PL group (2.7% vs. 5.0%, P < 0.05). NO3- supplementation reduced the O2 cost of moderate-intensity exercise and attenuated the decline in ramp incremental exercise performance following blood donation. These results have implications for improving functional capacity following blood loss.
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Author URL.
Thompson C, Vanhatalo A, Jell H, Fulford J, Carter J, Nyman L, Bailey SJ, Jones AM (2016). Dietary nitrate supplementation improves sprint and high-intensity intermittent running performance. Nitric Oxide: Biology and Chemistry, 61, 55-61.
Ferguson SK, Holdsworth CT, Colburn TD, Wright JL, Craig JC, Fees A, Jones AM, Allen JD, Musch TI, Poole DC, et al (2016). Dietary nitrate supplementation: impact on skeletal muscle vascular control in exercising rats with chronic heart failure.
J Appl Physiol (1985),
121(3), 661-669.
Abstract:
Dietary nitrate supplementation: impact on skeletal muscle vascular control in exercising rats with chronic heart failure.
Chronic heart failure (CHF) results in central and peripheral derangements that ultimately reduce skeletal muscle O2 delivery and impair exercise tolerance. Dietary nitrate (NO3 (-)) supplementation improves skeletal muscle vascular function and tolerance to exercise. We tested the hypothesis that NO3 (-) supplementation would elevate exercising skeletal muscle blood flow (BF) and vascular conductance (VC) in CHF rats. Myocardial infarction (MI) was induced (coronary artery ligation) in young adult male rats. After 21 days of recovery, rats randomly received 5 days of NO3 (-)-rich beetroot juice (CHF + BR, n = 10) or a placebo (CHF, n = 10). Mean arterial pressure (carotid artery catheter) and skeletal muscle BF (radiolabeled microspheres) were measured during treadmill exercise (20 m/min, 5% grade). CHF-induced dysfunction, as determined by myocardial infarction size (29 ± 3% and 33 ± 4% in CHF and CHF + BR, respectively) and left ventricular end-diastolic pressure (18 ± 2 and 18 ± 2 mmHg in CHF and CHF + BR, respectively), and exercising mean arterial pressure (131 ± 3 and 128 ± 4 mmHg in CHF and CHF + BR, respectively) were not different (P > 0.05) between groups. Total exercising hindlimb skeletal muscle BF (95 ± 5 and 116 ± 9 ml·min(-1)·100 g(-1) in CHF and CHF + BR, respectively) and VC (0.75 ± 0.05 and 0.90 ± 0.05 ml·min(-1)·100 g(-1)·mmHg(-1) in CHF and CHF + BR, respectively) were 22% and 20% greater in BR-supplemented rats, respectively (P < 0.05). During exercise, BF in 9 and VC in 10 hindlimb muscles and muscle portions were significantly greater in the CHF + BR group. These results provide strong evidence that dietary NO3 (-) supplementation improves skeletal muscle vascular function during exercise in rats with CHF and, thus, support the use of BR as a novel therapeutic modality for the treatment of CHF.
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Author URL.
Wylie LJ, Ortiz de Zevallos J, Isidore T, Nyman L, Vanhatalo A, Bailey SJ, Jones AM (2016). Dose-dependent effects of dietary nitrate on the oxygen cost of moderate-intensity exercise: Acute vs. chronic supplementation.
Nitric Oxide,
57, 30-39.
Abstract:
Dose-dependent effects of dietary nitrate on the oxygen cost of moderate-intensity exercise: Acute vs. chronic supplementation.
PURPOSE: to investigate whether chronic supplementation with a low or moderate dose of dietary nitrate (NO3(-)) reduces submaximal exercise oxygen uptake (V˙O2) and to assess whether or not this is dependent on acute NO3(-) administration prior to exercise. METHODS: Following baseline tests, 34 healthy subjects were allocated to receive 3 mmol NO3(-), 6 mmol NO3(-) or placebo. Two hours following the first ingestion, and after 7, 28 and 30 days of supplementation, subjects completed two moderate-intensity step exercise tests. On days 28 and 30, subjects in the NO3(-) groups completed the test 2 h post consumption of a NO3(-) dose (CHR + ACU) and a placebo dose (CHR). RESULTS: Plasma nitrite concentration ([NO2(-)]) was elevated in a dose-dependent manner at 2 h, 7 days and 28-30 days on the CHR + ACU visit. Compared to pre-treatment baseline, 6 mmol NO3(-) reduced the steady-state V˙O2 during moderate-intensity exercise by 3% at 2 h (P = 0.06), 7 days and at 28-30 days (both P
Abstract.
Author URL.
Jones AM, Ferguson SK, Bailey SJ, Vanhatalo A, Poole DC (2016). Fiber Type-Specific Effects of Dietary Nitrate.
Exerc Sport Sci Rev,
44(2), 53-60.
Abstract:
Fiber Type-Specific Effects of Dietary Nitrate.
Dietary nitrate supplementation increases circulating nitrite concentration, and the subsequent reduction of nitrite to nitric oxide is promoted in hypoxic environments. Given that PO2 is lower in Type II compared with Type I muscle, this article examines the hypothesis that the ergogenicity of nitrate supplementation is linked to specific effects on vascular, metabolic, and contractile function in Type II muscle.
Abstract.
Author URL.
Bailey SJ, Blackwell JR, Wylie LJ, Holland T, Winyard PG, Jones AM (2016). Improvement in blood pressure after short-term inorganic nitrate supplementation is attenuated in cigarette smokers compared to non-smoking controls.
Nitric Oxide,
61, 29-37.
Abstract:
Improvement in blood pressure after short-term inorganic nitrate supplementation is attenuated in cigarette smokers compared to non-smoking controls.
Dietary supplementation with inorganic nitrate (NO3-) has been reported to improve cardiovascular health indices in healthy adults. Cigarette smoking increases circulating thiocyanate (SCN-), which has been suggested to competitively inhibit salivary nitrate (NO3-) uptake, a rate-limiting step in dietary NO3- metabolism. Therefore, this study tested the hypothesis that dietary NO3- supplementation would be less effective at increasing the circulating plasma nitrite concentration ([NO2-]) and lowering blood pressure in smokers (S) compared to non-smokers (NS). Nine healthy smokers and eight healthy non-smoking controls reported to the laboratory at baseline (CON) and following six day supplementation periods with 140 mL day-1 NO3--rich (8.4 mmol NO3- day-1; NIT) and NO3--depleted (0.08 mmol NO3- day-1; PLA) beetroot juice in a cross-over experiment. Plasma and salivary [SCN-] were elevated in smokers compared to non-smokers in all experimental conditions (P
Abstract.
Author URL.
Wylie LJ, Bailey SJ, Kelly J, Blackwell JR, Vanhatalo A, Jones AM (2016). Influence of beetroot juice supplementation on intermittent exercise performance.
Eur J Appl Physiol,
116(2), 415-425.
Abstract:
Influence of beetroot juice supplementation on intermittent exercise performance.
PURPOSE: This study tested the hypothesis that nitrate (NO3-) supplementation would improve performance during high-intensity intermittent exercise featuring different work and recovery intervals. METHOD: Ten male team-sport players completed high-intensity intermittent cycling tests during separate 5-day supplementation periods with NO3 (-)-rich beetroot juice (BR; 8.2 mmol NO3- day(-1)) and NO3 (-)-depleted beetroot juice (PL; 0.08 mmol NO3- day(-1)). Subjects completed: twenty-four 6-s all-out sprints interspersed with 24 s of recovery (24 × 6-s); seven 30-s all-out sprints interspersed with 240 s of recovery (7 × 30-s); and six 60-s self-paced maximal efforts interspersed with 60 s of recovery (6 × 60-s); on days 3, 4, and 5 of supplementation, respectively. RESULT: Plasma [NO2-] was 237% greater in the BR trials. Mean power output was significantly greater with BR relative to PL in the 24 × 6-s protocol (568 ± 136 vs. 539 ± 136 W; P < 0.05), but not during the 7 × 30-s (558 ± 95 vs. 562 ± 94 W) or 6 × 60-s (374 ± 57 vs. 375 ± 59 W) protocols (P > 0.05). The increase in blood [lactate] across the 24 × 6-s and 7 × 30-s protocols was greater with BR (P < 0.05), but was not different in the 6 × 60-s protocol (P > 0.05). CONCLUSION: BR might be ergogenic during repeated bouts of short-duration maximal-intensity exercise interspersed with short recovery periods, but not necessarily during longer duration intervals or when a longer recovery duration is applied. These findings suggest that BR might have implications for performance enhancement during some types of intermittent exercise.
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Author URL.
Moore IS, Jones AM, Dixon SJ (2016). Reduced oxygen cost of running is related to alignment of the resultant GRF and leg axis vector: a pilot study.
Scand J Med Sci Sports,
26(7), 809-815.
Abstract:
Reduced oxygen cost of running is related to alignment of the resultant GRF and leg axis vector: a pilot study.
This pilot study investigated whether a 10-week running program (10wkRP), which reduced the oxygen cost of running, affected resultant ground reaction force (GRF), leg axis alignment, joint moment characteristics, and gear ratios. Ten novice, female runners completed a 10wkRP. Running kinematics and kinetics, in addition to oxygen consumption ( V ˙ O 2 ) during steady-state running, were recorded pre- and post-10wkRP. V ˙ O 2 decreased (8%) from pre-10wkRP to post-10wkRP. There was a better alignment of the resultant GRF and leg axis at peak propulsion post-10wkRP compared with pre-10wkRP (10.8 ± 4.9 vs 1.6 ± 1.2°), as the resultant GRF vector was applied 7 ± 0.6° (P = 0.008) more horizontally. There were shorter external ankle moment arms (24%) and smaller knee extensor moments (23%) at peak braking post-10wkRP. The change in V ˙ O 2 was associated with the change in alignment of the resultant GRF and leg axis (rs = 0.88, P = 0.003). As runners became more economical, they exhibited a more aligned resultant GRF vector and leg axis at peak propulsion. This appears to be a self-optimization strategy that may improve performance. Additionally, changes to external ankle moment arms indicated beneficial low gear ratios were achieved at the time of peak braking force.
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Author URL.
Ferguson SK, Glean AA, Holdsworth CT, Wright JL, Fees AJ, Colburn TD, Stabler T, Allen JD, Jones AM, Musch TI, et al (2016). Skeletal Muscle Vascular Control During Exercise: Impact of Nitrite Infusion During Nitric Oxide Synthase Inhibition in Healthy Rats.
J Cardiovasc Pharmacol Ther,
21(2), 201-208.
Abstract:
Skeletal Muscle Vascular Control During Exercise: Impact of Nitrite Infusion During Nitric Oxide Synthase Inhibition in Healthy Rats.
The nitric oxide synthase (NOS)-independent pathway of nitric oxide (NO) production in which nitrite (NO2 (-)) is reduced to NO may have therapeutic applications for those with cardiovascular diseases in which the NOS pathway is downregulated. We tested the hypothesis that NO2 (-) infusion would reduce mean arterial pressure (MAP) and increase skeletal muscle blood flow (BF) and vascular conductance (VC) during exercise in the face of NOS blockade via L-NAME. Following infusion of L-NAME (10 mg kg(-1), L-NAME), male Sprague-Dawley rats (3-6 months, n = 8) exercised without N(G)-nitro-L arginine methyl ester (L-NAME) and after infusion of sodium NO2 (-) (7 mg kg(-1); L-NAME + NO2 (-)). MAP and hindlimb skeletal muscle BF (radiolabeled microsphere infusions) were measured during submaximal treadmill running (20 m min(-1), 5% grade). Across group comparisons were made with a published control data set (n = 11). Relative to L-NAME, NO2 (-) infusion significantly reduced MAP (P < 0.03). The lower MAP in L-NAME+NO2 (-) was not different from healthy control animals (control: 137 ± 3 L-NAME: 157 ± 7, L-NAME + NO2 (-): 136 ± 5 mm Hg). Also, NO2 (-) infusion significantly increased VC when compared to L-NAME (P < 0.03), ultimately negating any significant differences from control animals (control: 0.78 ± 0.05, L-NAME: 0.57 ± 0.03, L-NAME + NO2 (-); 0.69 ± 0.04 mL min(-1) 100 g(-1) mm Hg(-1)) with no apparent fiber-type preferential effect. Overall, hindlimb BF was decreased significantly by L-NAME; however, in L-NAME + NO2 (-), BF improved to a level not significantly different from healthy controls (control: 108 ± 8, L-NAME: 88 ± 3, L-NAME + NO2 (-): 94 ± 6 mL min(-1) 100 g(-1), P = 0.38 L-NAME vs L-NAME + NO2 (-)). Individuals with diseases that impair NOS activity, and thus vascular function, may benefit from a NO2 (-)-based therapy in which NO bioavailability is elevated in an NOS-independent manner.
Abstract.
Author URL.
Black MI, Jones AM, Kelly JA, Bailey SJ, Vanhatalo A (2016). The constant work rate critical power protocol overestimates ramp incremental exercise performance.
Eur J Appl Physiol,
116(11-12), 2415-2422.
Abstract:
The constant work rate critical power protocol overestimates ramp incremental exercise performance.
PURPOSE: the parameters of the power-duration relationship (i.e. the critical power, CP, and the curvature constant, W') may theoretically predict maximal performance capability for exercise above the CP. The CP and W' are associated with the parameters of oxygen uptake ([Formula: see text]O2) kinetics, which can be altered by manipulation of the work-rate forcing function. We tested the hypothesis that the CP and W' derived from constant work-rate (CWR) prediction trials would overestimate ramp incremental exercise performance. METHODS: Thirty subjects (males, n = 28; females, n = 2) performed a ramp incremental test, and 3-5 CWR prediction trials for the determination of the CP and W'. Multiple ramp incremental tests and corresponding CP and W' estimates were available for some subjects such that in total 51 ramp test performances were predicted. RESULTS: the ramp incremental test performance (729 ± 113 s) was overestimated by the CP and W' estimates derived from the best (751 ± 114 s, P
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Author URL.
Vanhatalo A, Black MI, DiMenna FJ, Blackwell JR, Schmidt JF, Thompson C, Wylie LJ, Mohr M, Bangsbo J, Krustrup P, et al (2016). The mechanistic bases of the power-time relationship: muscle metabolic responses and relationships to muscle fibre type.
Journal of PhysiologyAbstract:
The mechanistic bases of the power-time relationship: muscle metabolic responses and relationships to muscle fibre type
We hypothesised that: 1) the critical power (CP) will represent a boundary separating steady state from non-steady state muscle metabolic responses during whole-body exercise and 2) that the CP and the W′ (curvature constant of the power-time relationship for high-intensity exercise) will be correlated with type I and type IIx muscle fibre distributions, respectively. Four men and four women performed a 3-min all-out cycling test for the estimation of CP and constant work rate (CWR) tests slightly >CP until exhaustion (Tlim), slightly CP Tlim isotime to test hypothesis 1. Eleven men performed 3-min all-out tests and donated muscle biopsies to test hypothesis 2. Below CP, muscle [PCr] (42.6±7.1 vs 49.4±6.9 mmol/kgDW), [La-] (34.8±12.6 vs 35.5±13.2 mmol/kgDW) and pH (7.11±0.08 vs 7.10±0.11) remained stable between ~12 and 24 min (P>0.05 for all), whereas these variables changed with time >CP such that they were greater ([La-] 95.6±14.1 mmol/kgDW) and lower ([PCr] 24.2±3.9 mmol/kgDW; pH 6.84±0.06) (P
Abstract.
Bailey SJ, Blackwell JR, Williams E, Vanhatalo A, Wylie LJ, Winyard PG, Jones AM (2016). Two weeks of watermelon juice supplementation improves nitric oxide bioavailability but not endurance exercise performance in humans. Nitric Oxide, 59, 10-20.
Cermak NM, Hansen D, Kouw IWK, van Dijk JW, Blackwell JR, Jones AM, Gibala MJ, van Loon LJC (2015). A single dose of sodium nitrate does not improve oral glucose tolerance in patients with type 2 diabetes mellitus.
Nutrition Research,
35(8), 674-680.
Abstract:
A single dose of sodium nitrate does not improve oral glucose tolerance in patients with type 2 diabetes mellitus
Dietary nitrate (NO3-) supplementation has been proposed as an emerging treatment strategy for type 2 diabetes. We hypothesized that ingestion of a single bolus of dietary NO3- ingestion improves oral glucose tolerance in patients with type 2 diabetes. Seventeen men with type 2 diabetes (glycated hemoglobin, 7.3% ± 0.2%) participated in a randomized crossover experiment. The subjects ingested a glucose beverage 2.5 hours after consumption of either sodium NO3- (0.15 mmol NaNO3- · kg-1) or a placebo solution. Venous blood samples were collected before ingestion of the glucose beverage and every 30 minutes thereafter during a 2-hour period to assess postprandial plasma glucose and insulin concentrations. The results show that plasma NO3- and nitrite levels were increased after NaNO3- as opposed to placebo ingestion (treatment-effect, P =. 001). Despite the elevated plasma NO3- and nitrite levels, ingestion of NaNO3- did not attenuate the postprandial rise in plasma glucose and insulin concentrations (time × treatment interaction, P =. 41 for glucose, P =. 93 for insulin). Despite the lack of effect on oral glucose tolerance, basal plasma glucose concentrations measured 2.5 hours after NaNO3- ingestion were lower when compared with the placebo treatment (7.5 ± 0.4 vs 8.3 ± 0.4 mmol/L, respectively; P =. 04). We conclude that ingestion of a single dose of dietary NO3- does not improve subsequent oral glucose tolerance in patients with type 2 diabetes.
Abstract.
Cermak NM, Hansen D, Kouw IWK, van Dijk J-W, Blackwell JR, Jones AM, Gibala MJ, van Loon LJC (2015). A single dose of sodium nitrate does not improve oral glucose tolerance in patients with type 2 diabetes mellitus.
Nutr Res,
35(8), 674-680.
Abstract:
A single dose of sodium nitrate does not improve oral glucose tolerance in patients with type 2 diabetes mellitus.
Dietary nitrate (NO3(-)) supplementation has been proposed as an emerging treatment strategy for type 2 diabetes. We hypothesized that ingestion of a single bolus of dietary NO3(-) ingestion improves oral glucose tolerance in patients with type 2 diabetes. Seventeen men with type 2 diabetes (glycated hemoglobin, 7.3% ± 0.2%) participated in a randomized crossover experiment. The subjects ingested a glucose beverage 2.5 hours after consumption of either sodium NO3(-) (0.15 mmol NaNO3(-) · kg(-1)) or a placebo solution. Venous blood samples were collected before ingestion of the glucose beverage and every 30 minutes thereafter during a 2-hour period to assess postprandial plasma glucose and insulin concentrations. The results show that plasma NO3(-) and nitrite levels were increased after NaNO3(-) as opposed to placebo ingestion (treatment-effect, P =. 001). Despite the elevated plasma NO3(-) and nitrite levels, ingestion of NaNO3(-) did not attenuate the postprandial rise in plasma glucose and insulin concentrations (time × treatment interaction, P =. 41 for glucose, P =. 93 for insulin). Despite the lack of effect on oral glucose tolerance, basal plasma glucose concentrations measured 2.5 hours after NaNO3(-) ingestion were lower when compared with the placebo treatment (7.5 ± 0.4 vs 8.3 ± 0.4 mmol/L, respectively; P =. 04). We conclude that ingestion of a single dose of dietary NO3(-) does not improve subsequent oral glucose tolerance in patients with type 2 diabetes.
Abstract.
Author URL.
Blackwell J, Harries LW, Pilling LC, Ferrucci L, Jones A, Melzer D (2015). Changes in CEBPB expression in circulating leukocytes following eccentric elbow-flexion exercise.
Journal of Physiological Sciences,
65(1), 145-150.
Abstract:
Changes in CEBPB expression in circulating leukocytes following eccentric elbow-flexion exercise
In mouse models, CCAAT enhancer-binding protein beta (CEBPB) is necessary for M2 macrophage-mediated regeneration after muscle injury. In humans, CEBPB expression in blood was strongly associated with muscle strength. In this study we aimed to test whether CEBPB expression in blood in people is increased 2 days after exercise designed to induce muscle damage and subsequent repair. Sixteen healthy male volunteers undertook elbow flexor exercises designed to induce acute muscle micro-damage. Peripheral blood samples were collected at baseline and days 1, 2, 4 and 7 following exercise. Expression of CEBPB and related genes were analysed by qRT-PCR. Extent of muscle damage was determined by decline in maximal voluntary isometric torque and by plasma creatine kinase activity. Nine subjects had peak (day 4) creatine kinase activity exceeding 10,000 U/l. In this subgroup, CEBPB expression was elevated from baseline to 2 days post exercise (paired-samples t(1,8) = 3.72, p = 0.006). Related expression and selected cytokine changes after exercise did not reach significance. Muscle-damaging exercise in humans can be followed by induction of CEBPB transcript expression in peripheral blood. Associations between CEBPB expression in blood and muscle strength may be consistent with the CEBPB-dependent muscle repair process.
Abstract.
Blackwell J, Harries LW, Pilling LC, Ferrucci L, Jones A, Melzer D (2015). Changes in CEBPB expression in circulating leukocytes following eccentric elbow-flexion exercise.
J Physiol Sci,
65(1), 145-150.
Abstract:
Changes in CEBPB expression in circulating leukocytes following eccentric elbow-flexion exercise.
In mouse models, CCAAT enhancer-binding protein beta (CEBPB) is necessary for M2 macrophage-mediated regeneration after muscle injury. In humans, CEBPB expression in blood was strongly associated with muscle strength. In this study we aimed to test whether CEBPB expression in blood in people is increased 2 days after exercise designed to induce muscle damage and subsequent repair. Sixteen healthy male volunteers undertook elbow flexor exercises designed to induce acute muscle micro-damage. Peripheral blood samples were collected at baseline and days 1, 2, 4 and 7 following exercise. Expression of CEBPB and related genes were analysed by qRT-PCR. Extent of muscle damage was determined by decline in maximal voluntary isometric torque and by plasma creatine kinase activity. Nine subjects had peak (day 4) creatine kinase activity exceeding 10,000 U/l. In this subgroup, CEBPB expression was elevated from baseline to 2 days post exercise (paired-samples t (1,8) = 3.72, p = 0.006). Related expression and selected cytokine changes after exercise did not reach significance. Muscle-damaging exercise in humans can be followed by induction of CEBPB transcript expression in peripheral blood. Associations between CEBPB expression in blood and muscle strength may be consistent with the CEBPB-dependent muscle repair process.
Abstract.
Author URL.
Ashworth A, Bailey SJ, Hayward GM, DiMenna F, Vanhatalo A, Jones AM (2015). Dietary nitrate - an unrecognized nutrient?.
Clin Nutr ESPEN,
10(5).
Author URL.
Thompson C, Wylie LJ, Fulford J, Kelly J, Black MI, McDonagh STJ, Jeukendrup AE, Vanhatalo A, Jones AM (2015). Dietary nitrate improves sprint performance and cognitive function during prolonged intermittent exercise.
Eur J Appl Physiol,
115(9), 1825-1834.
Abstract:
Dietary nitrate improves sprint performance and cognitive function during prolonged intermittent exercise.
UNLABELLED: it is possible that dietary nitrate (NO3 (-)) supplementation may improve both physical and cognitive performance via its influence on blood flow and cellular energetics. PURPOSE: to investigate the effects of dietary NO3 (-) supplementation on exercise performance and cognitive function during a prolonged intermittent sprint test (IST) protocol, which was designed to reflect typical work patterns during team sports. METHODS: in a double-blind randomised crossover study, 16 male team-sport players received NO3 (-)-rich (BR; 140 mL day(-1); 12.8 mmol of NO3 (-)), and NO3 (-)-depleted (PL; 140 mL day(-1); 0.08 mmol NO3 (-)) beetroot juice for 7 days. On day 7 of supplementation, subjects completed the IST (two 40-min "halves" of repeated 2-min blocks consisting of a 6-s "all-out" sprint, 100-s active recovery and 20 s of rest), on a cycle ergometer during which cognitive tasks were simultaneously performed. RESULTS: Total work done during the sprints of the IST was greater in BR (123 ± 19 kJ) compared to PL (119 ± 17 kJ; P < 0.05). Reaction time of response to the cognitive tasks in the second half of the IST was improved in BR compared to PL (BR first half: 820 ± 96 vs. second half: 817 ± 86 ms; PL first half: 824 ± 114 vs. second half: 847 ± 118 ms; P < 0.05). There was no difference in response accuracy. CONCLUSIONS: These findings suggest that dietary NO3 (-) enhances repeated sprint performance and may attenuate the decline in cognitive function (and specifically reaction time) that may occur during prolonged intermittent exercise.
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Author URL.
Wightman EL, Haskell-Ramsay CF, Thompson KG, Blackwell JR, Winyard PG, Forster J, Jones AM, Kennedy DO (2015). Dietary nitrate modulates cerebral blood flow parameters and cognitive performance in humans: a double-blind, placebo-controlled, crossover investigation.
Physiol Behav,
149, 149-158.
Abstract:
Dietary nitrate modulates cerebral blood flow parameters and cognitive performance in humans: a double-blind, placebo-controlled, crossover investigation.
Nitrate derived from vegetables is consumed as part of a normal diet and is reduced endogenously via nitrite to nitric oxide. It has been shown to improve endothelial function, reduce blood pressure and the oxygen cost of sub-maximal exercise, and increase regional perfusion in the brain. The current study assessed the effects of dietary nitrate on cognitive performance and prefrontal cortex cerebral blood-flow (CBF) parameters in healthy adults. In this randomised, double-blind, placebo-controlled, parallel-groups study, 40 healthy adults received either placebo or 450 ml beetroot juice (~5.5 mmol nitrate). Following a 90 minute drink/absorption period, participants performed a selection of cognitive tasks that activate the frontal cortex for 54 min. Near-Infrared Spectroscopy (NIRS) was used to monitor CBF and hemodynamics, as indexed by concentration changes in oxygenated and deoxygenated-haemoglobin, in the frontal cortex throughout. The bioconversion of nitrate to nitrite was confirmed in plasma by ozone-based chemi-luminescence. Dietary nitrate modulated the hemodynamic response to task performance, with an initial increase in CBF at the start of the task period, followed by consistent reductions during the least demanding of the three tasks utilised. Cognitive performance was improved on the serial 3s subtraction task. These results show that single doses of dietary nitrate can modulate the CBF response to task performance and potentially improve cognitive performance, and suggest one possible mechanism by which vegetable consumption may have beneficial effects on brain function.
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Author URL.
Shepherd AI, Gilchrist M, Winyard PG, Jones AM, Hallmann E, Kazimierczak R, Rembialkowska E, Benjamin N, Shore AC, Wilkerson DP, et al (2015). Effects of dietary nitrate supplementation on the oxygen cost of exercise and walking performance in individuals with type 2 diabetes: a randomized, double-blind, placebo-controlled crossover trial.
Free Radic Biol Med,
86, 200-208.
Abstract:
Effects of dietary nitrate supplementation on the oxygen cost of exercise and walking performance in individuals with type 2 diabetes: a randomized, double-blind, placebo-controlled crossover trial.
Dietary nitrate supplementation has been shown to reduce the oxygen (O2) cost of exercise and enhance exercise tolerance in healthy individuals. This study assessed whether similar effects could be observed in individuals with type 2 diabetes (T2DM). In a randomized, double-blind, placebo-controlled crossover study, 48 participants with T2DM supplemented their diet for 4 days with either nitrate-rich beetroot juice (70ml/day, 6.43mmol nitrate/day) or nitrate-depleted beetroot juice as placebo (70ml/day, 0.07mmol nitrate/day). After each intervention period, resting plasma nitrate and nitrite concentrations were measured subsequent to participants completing moderate-paced walking. Pulmonary gas exchange was measured to assess the O2 cost of walking. After a rest period, participants performed the 6-min walk test (6MWT). Relative to placebo, beetroot juice resulted in a significant increase in plasma nitrate (placebo, 57±66 vs beetroot, 319±110µM; P < 0.001) and plasma nitrite concentration (placebo, 680±256 vs beetroot, 1065±607nM; P < 0.001). There were no differences between placebo juice and beetroot juice for the O2 cost of walking (946±221 vs 939±223ml/min, respectively; P = 0.59) and distance covered in the 6MWT (550±83 vs 554±90m, respectively; P = 0.17). Nitrate supplementation did not affect the O2 cost of moderate-paced walking or improve performance in the 6MWT. These findings indicate that dietary nitrate supplementation does not modulate the response to exercise in individuals with T2DM.
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Author URL.
Ashworth A, Mitchell K, Blackwell JR, Vanhatalo A, Jones AM (2015). High-nitrate vegetable diet increases plasma nitrate and nitrite concentrations and reduces blood pressure in healthy women.
Public Health Nutrition,
18(14), 2669-2678.
Abstract:
High-nitrate vegetable diet increases plasma nitrate and nitrite concentrations and reduces blood pressure in healthy women
Objective Epidemiological studies suggest that green leafy vegetables, which are high in dietary nitrate, are protective against CVD such as stroke. High blood pressure (BP) is a major risk factor for stroke and inorganic nitrate has been shown to reduce BP. The objective of the present study was to test the hypothesis that diets containing high-nitrate (HN) vegetables would increase plasma nitrate and nitrite concentrations and reduce BP in healthy women. Design a randomized, crossover trial, where participants received HN vegetables (HN diet) or avoided HN vegetables (Control diet) for 1 week. Before and after each intervention, resting BP and plasma nitrate and nitrite concentrations were measured. Setting University of Exeter, UK. Subjects Nineteen healthy women (mean age 20 (sd 2) years; mean BMI 22·5 (sd 3·8) kg/m2). Results the HN diet significantly increased plasma nitrate concentration (before HN diet: mean 24·4 (sd 5·6) mol/l; after HN diet: mean 61·0 (sd 44·1) mol/l, P
Abstract.
Ashworth A, Mitchell K, Blackwell JR, Vanhatalo A, Jones AM (2015). High-nitrate vegetable diet increases plasma nitrate and nitrite concentrations and reduces blood pressure in healthy women.
Public Health Nutr,
18(14), 2669-2678.
Abstract:
High-nitrate vegetable diet increases plasma nitrate and nitrite concentrations and reduces blood pressure in healthy women.
OBJECTIVE: Epidemiological studies suggest that green leafy vegetables, which are high in dietary nitrate, are protective against CVD such as stroke. High blood pressure (BP) is a major risk factor for stroke and inorganic nitrate has been shown to reduce BP. The objective of the present study was to test the hypothesis that diets containing high-nitrate (HN) vegetables would increase plasma nitrate and nitrite concentrations and reduce BP in healthy women. DESIGN: a randomized, crossover trial, where participants received HN vegetables (HN diet) or avoided HN vegetables (Control diet) for 1 week. Before and after each intervention, resting BP and plasma nitrate and nitrite concentrations were measured. SETTING: University of Exeter, UK. SUBJECTS: Nineteen healthy women (mean age 20 (sd 2) years; mean BMI 22·5 (sd 3·8) kg/m2). RESULTS: the HN diet significantly increased plasma nitrate concentration (before HN diet: mean 24·4 (sd 5·6) µmol/l; after HN diet: mean 61·0 (sd 44·1) µmol/l, P
Abstract.
Author URL.
Kilpatrick MW, Martinez N, Little JP, Jung ME, Jones AM, Price NW, Lende DH (2015). Impact of high-intensity interval duration on perceived exertion.
Med Sci Sports Exerc,
47(5), 1038-1045.
Abstract:
Impact of high-intensity interval duration on perceived exertion.
PURPOSE: RPE is increasingly being considered as a viable tool beyond its original use for monitoring in-task exercise intensity. Research indicates that anticipated, in-task, and postexercise RPE values are often notably different from one another. An important new consideration is how perceptions are impacted by high-intensity interval training (HIT). This study aims to compare RPE responses before, during, and after continuous and HIT exercise trials. METHODS: Twenty (11 females and 9 males; mean ± SD age, 22 ± 4 yr) overweight (mean ± SD body mass index, 29 ± 3 kg·m(-2)) and unfit (mean ± SD V˙O2peak, 28 ± 5 mL·kg·min(-1)) participants completed a 20-min heavy continuous (HC) trial and three 24-min severe-intensity interval trials that utilized 1:1 work-to-recovery ratios: 30 s (Severe Interval-30), 60 s (Severe Interval-60), and 120 s (Severe Interval-120). Exertion was assessed using the Borg CR10 Scale. Data were analyzed using repeated-measures ANOVA and pairwise comparisons. RESULTS: Anticipated exertion was highest in the Severe Interval-120 trial (5.8 ± 2.0; P < 0.05) compared with other trials. Exertion increased from beginning to end in all trials (P < 0.05), with the greatest increases observed within the HC trial. Session RPE for the Severe Interval-120 trial (6.4 ± 2.3) was higher than those for all other trials (P < 0.05), and session RPE for the Severe Interval-30 trial (3.7 ± 1.8) was lower than that for the HC trial (4.9 ± 1.6; P < 0.05). CONCLUSIONS: These findings suggest that 30-s HIT protocols limit the perceptual drift that occurs during exercise, in comparison to HC exercise. Moreover, performing more intervals of shorter durations appears to produce lower postexercise RPE values than performing fewer intervals of longer duration and equal intensity. Because effort perception may influence behavior, these results could have implications for the prescription of interval training in overweight sedentary adults.
Abstract.
Author URL.
Simpson LP, Jones AM, Skiba PF, Vanhatalo A, Wilkerson D (2015). Influence of hypoxia on the power-duration relationship during high-intensity exercise.
Int J Sports Med,
36(2), 113-119.
Abstract:
Influence of hypoxia on the power-duration relationship during high-intensity exercise.
We investigated the influence of hypoxia on the asymptote (critical power, CP) and the curvature constant (W') of the hyperbolic power-duration relationship, as measured by both conventional and all-out testing procedures. 13 females completed 5 constant-power prediction trials and a 3-min all-out test to estimate CP and W', in both normoxia (N) and moderate hypoxia (H; FiO2=0.13). CP was significantly reduced in hypoxia compared to normoxia when estimated by conventional (H:132±17 vs. N:175±25 W; P
Abstract.
Author URL.
Bailey SJ, Varnham RL, DiMenna FJ, Breese BC, Wylie LJ, Jones AM (2015). Inorganic nitrate supplementation improves muscle oxygenation, O₂ uptake kinetics, and exercise tolerance at high but not low pedal rates.
J Appl Physiol (1985),
118(11), 1396-1405.
Abstract:
Inorganic nitrate supplementation improves muscle oxygenation, O₂ uptake kinetics, and exercise tolerance at high but not low pedal rates.
We tested the hypothesis that inorganic nitrate (NO3 (-)) supplementation would improve muscle oxygenation, pulmonary oxygen uptake (V̇o2) kinetics, and exercise tolerance (Tlim) to a greater extent when cycling at high compared with low pedal rates. In a randomized, placebo-controlled cross-over study, seven subjects (mean ± SD, age 21 ± 2 yr, body mass 86 ± 10 kg) completed severe-intensity step cycle tests at pedal cadences of 35 rpm and 115 rpm during separate nine-day supplementation periods with NO3 (-)-rich beetroot juice (BR) (providing 8.4 mmol NO3 (-)/day) and placebo (PLA). Compared with PLA, plasma nitrite concentration increased 178% with BR (P < 0.01). There were no significant differences in muscle oxyhemoglobin concentration ([O2Hb]), phase II V̇o2 kinetics, or Tlim between BR and PLA when cycling at 35 rpm (P > 0.05). However, when cycling at 115 rpm, muscle [O2Hb] was higher at baseline and throughout exercise, phase II V̇o2 kinetics was faster (47 ± 16 s vs. 61 ± 25 s; P < 0.05), and Tlim was greater (362 ± 137 s vs. 297 ± 79 s; P < 0.05) with BR compared with PLA. These results suggest that short-term BR supplementation can increase muscle oxygenation, expedite the adjustment of oxidative metabolism, and enhance exercise tolerance when cycling at a high, but not a low, pedal cadence in healthy recreationally active subjects. These findings support recent observations that NO3 (-) supplementation may be particularly effective at improving physiological and functional responses in type II muscle fibers.
Abstract.
Author URL.
Skiba PF, Fulford J, Clarke DC, Vanhatalo A, Jones AM (2015). Intramuscular determinants of the ability to recover work capacity above critical power.
European Journal of Applied Physiology,
115(4), 703-713.
Abstract:
Intramuscular determinants of the ability to recover work capacity above critical power
Purpose: the primary purpose of this investigation was to compare the recovery of the W′ to the recovery of intramuscular substrates and metabolites using 31P- and 1H-magnetic resonance spectroscopy. Methods: Ten healthy recreationally trained subjects were tested to determine critical power (CP) and W′ for single-leg-extensor exercise. They subsequently exercised in the bore of a 1.5-T MRI scanner at a supra-CP work rate. Following exhaustion, the subjects rested in place for 1, 2, 5 or 7 min, and then repeated the effort. The temporal course of W′ recovery was estimated, which was then compared to the recovery of creatine phosphate [PCr], pH, carnosine content, and to the output of a novel derivation of the W′BAL model. Results: W′ recovery closely correlated with the predictions of the novel model (r = 0.97, p = 0.03). [PCr] recovered faster (Formula presented.) than W′(Formula presented.) the W′ available for the second exercise bout was directly correlated with the difference between [PCr] at the beginning of the work bout and [PCr] at exhaustion (r = 0.99, p = 0.005). Nonlinear regression revealed an inverse curvilinear relationship between carnosine concentration and the W′t1/2 (r2 = 0.55). Conclusion: the kinetics of W′ recovery in single-leg-extensor exercise is comparable to that observed in whole-body exercise, suggesting a conserved mechanism. The extent to which the recovery of the W′ can be directly attributed to the recovery of [PCr] is unclear. The relationship of the W′ to muscle carnosine content suggests novel future avenues of investigation.
Abstract.
Skiba PF, Fulford J, Clarke DC, Vanhatalo A, Jones AM (2015). Intramuscular determinants of the ability to recover work capacity above critical power.
Eur J Appl Physiol,
115(4), 703-713.
Abstract:
Intramuscular determinants of the ability to recover work capacity above critical power.
PURPOSE: the primary purpose of this investigation was to compare the recovery of the W' to the recovery of intramuscular substrates and metabolites using (31)P- and (1)H-magnetic resonance spectroscopy. METHODS: Ten healthy recreationally trained subjects were tested to determine critical power (CP) and W' for single-leg-extensor exercise. They subsequently exercised in the bore of a 1.5-T MRI scanner at a supra-CP work rate. Following exhaustion, the subjects rested in place for 1, 2, 5 or 7 min, and then repeated the effort. The temporal course of W' recovery was estimated, which was then compared to the recovery of creatine phosphate [PCr], pH, carnosine content, and to the output of a novel derivation of the W' BAL model. RESULTS: W' recovery closely correlated with the predictions of the novel model (r = 0.97, p = 0.03). [PCr] recovered faster [Formula: see text] than W' [Formula: see text] the W' available for the second exercise bout was directly correlated with the difference between [PCr] at the beginning of the work bout and [PCr] at exhaustion (r = 0.99, p = 0.005). Nonlinear regression revealed an inverse curvilinear relationship between carnosine concentration and the W' t 1/2 (r (2) = 0.55). CONCLUSION: the kinetics of W' recovery in single-leg-extensor exercise is comparable to that observed in whole-body exercise, suggesting a conserved mechanism. The extent to which the recovery of the W' can be directly attributed to the recovery of [PCr] is unclear. The relationship of the W' to muscle carnosine content suggests novel future avenues of investigation.
Abstract.
Author URL.
Hunter SK, Joyner MJ, Jones AM (2015). Last Word on Viewpoint: the two-hour marathon: What's the equivalent for women?.
J Appl Physiol (1985),
118(10).
Author URL.
Ferguson SK, Holdsworth CT, Wright JL, Fees AJ, Allen JD, Jones AM, Musch TI, Poole DC (2015). Microvascular oxygen pressures in muscles comprised of different fiber types: Impact of dietary nitrate supplementation.
Nitric Oxide,
48, 38-43.
Abstract:
Microvascular oxygen pressures in muscles comprised of different fiber types: Impact of dietary nitrate supplementation.
Nitrate (NO3(-)) supplementation via beetroot juice (BR) preferentially improves vascular conductance and O2 delivery to contracting skeletal muscles comprised predominantly of type IIb + d/x (i.e. highly glycolytic) fibers following its reduction to nitrite and nitric oxide (NO). To address the mechanistic basis for NO3(-) to improve metabolic control we tested the hypothesis that BR supplementation would elevate microvascular PO2 (PO2mv) in fast twitch but not slow twitch muscle. Twelve young adult male Sprague-Dawley rats were administered BR ([NO3(-)] 1 mmol/kg/day, n = 6) or water (control, n = 6) for 5 days. PO2mv (phosphorescence quenching) was measured at rest and during 180 s of electrically-induced 1-Hz twitch contractions (6-8 V) of the soleus (9% type IIb +d/x) and mixed portion of the gastrocnemius (MG, 91% type IIb + d/x) muscles. In the MG, but not the soleus, BR elevated contracting steady state PO2mv by ~43% (control: 14 ± 1, BR: 19 ± 2 mmHg (P < 0.05)). This higher PO2mv represents a greater blood-myocyte O2 driving force during muscle contractions thus providing a potential mechanism by which NO3(-) supplementation via BR improves metabolic control in fast twitch muscle. Recruitment of higher order type II muscle fibers is thought to play a role in the development of the VO2 slow component which is inextricably linked to the fatigue process. These data therefore provide a putative mechanism for the BR-induced improvements in high-intensity exercise performance seen in humans.
Abstract.
Author URL.
James PE, Willis GR, Allen JD, Winyard PG, Jones AM (2015). Nitrate pharmacokinetics: Taking note of the difference.
Nitric Oxide,
48, 44-50.
Abstract:
Nitrate pharmacokinetics: Taking note of the difference.
It is now recognised that administration of oral nitrate (NO3(-)), in its various forms, increases the level of nitric oxide (NO) metabolites in the circulation of humans. Its application to modulate physiology and alleviate cardiovascular dysfunction in some patients is now recorded and shows particular promise in hypertension, in modifying platelet activation/aggregation, and in conditions where tissue ischaemia prevails. The potential of oral NO3(-) to modify exercise/performance via elevation of plasma nitrite concentration ([NO2(-)]) has been applied across a range of human test systems. Herein we discuss how the choice of NO3(-) source, route of administration and resulting pharmacokinetics might influence the outcome of physiological measures and potentially contribute to discrepancies in performance trials. There are but a few examples of detailed pharmacokinetic data on which the majority of researchers base their test protocols in different cohorts/settings. We compare and contrast the results of key publications with the aim of highlighting a consensus of our current understanding and critical considerations for those entering the field.
Abstract.
Author URL.
Affourtit C, Bailey SJ, Jones AM, Smallwood MJ, Winyard PG (2015). On the mechanism by which dietary nitrate improves human skeletal muscle function.
Front Physiol,
6Abstract:
On the mechanism by which dietary nitrate improves human skeletal muscle function.
Inorganic nitrate is present at high levels in beetroot and celery, and in green leafy vegetables such as spinach and lettuce. Though long believed inert, nitrate can be reduced to nitrite in the human mouth and, further, under hypoxia and/or low pH, to nitric oxide. Dietary nitrate has thus been associated favorably with nitric-oxide-regulated processes including blood flow and energy metabolism. Indeed, the therapeutic potential of dietary nitrate in cardiovascular disease and metabolic syndrome-both aging-related medical disorders-has attracted considerable recent research interest. We and others have shown that dietary nitrate supplementation lowers the oxygen cost of human exercise, as less respiratory activity appears to be required for a set rate of skeletal muscle work. This striking observation predicts that nitrate benefits the energy metabolism of human muscle, increasing the efficiency of either mitochondrial ATP synthesis and/or of cellular ATP-consuming processes. In this mini-review, we evaluate experimental support for the dietary nitrate effects on muscle bioenergetics and we critically discuss the likelihood of nitric oxide as the molecular mediator of such effects.
Abstract.
Author URL.
Jones AM (2015). Oxygen uptake dynamics during exercise.
ACTA PHYSIOLOGICA,
215, 53-54.
Author URL.
Black MI, Jones AM, Bailey SJ, Vanhatalo A (2015). Self-pacing increases critical power and improves performance during severe-intensity exercise.
Appl Physiol Nutr Metab,
40(7), 662-670.
Abstract:
Self-pacing increases critical power and improves performance during severe-intensity exercise.
The parameters of the power-duration relationship for severe-intensity exercise (i.e. the critical power (CP) and the curvature constant (W')) are related to the kinetics of pulmonary O2 uptake, which may be altered by pacing strategy. We tested the hypothesis that the CP would be higher when derived from a series of self-paced time-trials (TT) than when derived from the conventional series of constant work-rate (CWR) exercise tests. Ten male subjects (age, 21.5 ± 1.9 years; mass, 75.2 ± 11.5 kg) completed 3-4 CWR and 3-4 TT prediction trial protocols on a cycle ergometer for the determination of the CP and W'. The CP derived from the TT protocol (265 ± 44 W) was greater (P < 0.05) than the CP derived from the CWR protocol (250 ± 47 W), while the W' was not different between protocols (TT: 18.1 ± 5.7 kJ, CWR: 20.6 ± 7.4 kJ, P > 0.05). The mean response time of pulmonary O2 uptake was shorter during the TTs than the CWR trials (TT: 34 ± 16, CWR: 39 ± 19 s, P < 0.05). The CP was correlated with the total O2 consumed in the first 60 s across both protocols (r = 0.88, P < 0.05, n = 20). These results suggest that in comparison with the conventional CWR exercise protocol, a self-selected pacing strategy enhances CP and improves severe-intensity exercise performance. The greater CP during TT compared with CWR exercise has important implications for performance prediction, suggesting that TT completion times may be overestimated by CP and W' parameters derived from CWR protocols.
Abstract.
Author URL.
McDonagh STJ, Wylie LJ, Winyard PG, Vanhatalo A, Jones AM (2015). The Effects of Chronic Nitrate Supplementation and the Use of Strong and Weak Antibacterial Agents on Plasma Nitrite Concentration and Exercise Blood Pressure.
Int J Sports Med,
36(14), 1177-1185.
Abstract:
The Effects of Chronic Nitrate Supplementation and the Use of Strong and Weak Antibacterial Agents on Plasma Nitrite Concentration and Exercise Blood Pressure.
Chlorhexidine-containing mouthwash (STRONG), which disturbs oral microflora, has been shown to diminish the rise in plasma nitrite concentration ([NO2-]) and attenuate the reduction in resting blood pressure (BP) typically seen after acute nitrate (NO3-) ingestion. We aimed to determine whether STRONG and weaker antiseptic agents attenuate the physiological effects of chronic NO3- supplementation using beetroot juice (BR). 12 healthy volunteers mouth-rinsed with STRONG, non-chlorhexidine mouthwash (WEAK) and deionised water (CON) 3 times a day, and ingested 70 mL BR (6.2 mmol NO3-), twice a day, for 6 days. BP (at rest and during 10 min of treadmill walking) and plasma and salivary [NO3-] and [NO2-] were measured prior to and on day 6 of supplementation. The change in salivary [NO3-] 4 h post final ingestion was higher (P
Abstract.
Author URL.
Shepherd AI, Wilkerson DP, Dobson L, Kelly J, Winyard PG, Jones AM, Benjamin N, Shore AC, Gilchrist M (2015). The effect of dietary nitrate supplementation on the oxygen cost of cycling, walking performance and resting blood pressure in individuals with chronic obstructive pulmonary disease: a double blind placebo controlled, randomised control trial.
Nitric Oxide,
48, 31-37.
Abstract:
The effect of dietary nitrate supplementation on the oxygen cost of cycling, walking performance and resting blood pressure in individuals with chronic obstructive pulmonary disease: a double blind placebo controlled, randomised control trial.
BACKGROUND: Chronic obstructive pulmonary disease (COPD) results in exercise intolerance. Dietary nitrate supplementation has been shown to lower blood pressure (BP), reduce the oxygen cost of exercise, and enhance exercise tolerance in healthy volunteers. This study assessed the effects of dietary nitrate on the oxygen cost of cycling, walking performance and BP in individuals with mild-moderate COPD. METHODS: Thirteen patients with mild-moderate COPD were recruited. Participants consumed 70 ml of either nitrate-rich (6.77 mmol nitrate; beetroot juice) or nitrate-depleted beetroot juice (0.002 mmol nitrate; placebo) twice a day for 2.5 days, with the final supplement ~3 hours before testing. BP was measured before completing two bouts of moderate-intensity cycling, where pulmonary gas exchange was measured throughout. The six-minute walk test (6 MWT) was completed 30 minutes subsequent to the second cycling bout. RESULTS: Plasma nitrate concentration was significantly elevated following beetroot juice vs. placebo (placebo; 48 ± 86 vs. beetroot juice; 215 ± 84 µM, P = 0.002). No significant differences were observed between placebo vs. beetroot juice for oxygen cost of exercise (933 ± 323 vs. 939 ± 302 ml: min(-1); P = 0.88), distance covered in the 6 MWT (456 ± 86 vs. 449 ± 79 m; P = 0.37), systolic BP (123 ± 14 vs. 123 ± 14 mmHg; P = 0.91), or diastolic BP (77 ± 9 vs. 79 ± 9 mmHg; P = 0.27). CONCLUSION: Despite a large rise in plasma nitrate concentration, two days of nitrate supplementation did not reduce the oxygen cost of moderate intensity cycling, increase distance covered in the 6 MWT, or lower BP.
Abstract.
Author URL.
Hunter SK, Joyner MJ, Jones AM (2015). The two-hour marathon: What's the equivalent for women?.
J Appl Physiol (1985),
118(10), 1321-1323.
Author URL.
Bailey SJ, Blackwell JR, Lord T, Vanhatalo A, Winyard PG, Jones AM (2015). l-Citrulline supplementation improves O2 uptake kinetics and high-intensity exercise performance in humans.
J Appl Physiol (1985),
119(4), 385-395.
Abstract:
l-Citrulline supplementation improves O2 uptake kinetics and high-intensity exercise performance in humans.
The purpose of this study was to compare the effects of l-citrulline (Cit) and l-arginine (Arg) supplementation on nitric oxide (NO) biomarkers, pulmonary O2 uptake (V̇o2) kinetics, and exercise performance. In a randomized, placebo (Pla)-controlled, crossover study, 10 healthy adult men completed moderate- and severe-intensity cycling exercise on days 6 and 7 of a 7-day supplementation period with Pla, Arg (6 g/day), and Cit (6 g/day). Compared with Pla, plasma Arg concentration was increased by a similar magnitude with Arg and Cit supplementation, but plasma Cit concentration was only increased (P < 0.001) with Cit supplementation. Plasma nitrite (NO2 (-)) concentration was increased with Arg supplementation (P < 0.05) and tended to increase with Cit supplementation (P = 0.08) compared with Pla (83 ± 25, 106 ± 41, and 100 ± 38 nM with Pla, Arg, and Cit, respectively); however, mean arterial blood pressure was only lower (P < 0.05) after Cit supplementation. The steady-state V̇o2 amplitude during moderate-intensity cycle exercise was not significantly different between supplements, but Cit lowered the V̇o2 mean response time (59 ± 8 and 53 ± 5 s with Pla and Cit, respectively, P < 0.05) during severe-intensity exercise, improved tolerance to severe-intensity exercise (589 ± 101 and 661 ± 107 s with Pla and Cit, respectively), and increased the total amount of work completed in the exercise performance test (123 ± 18 and 125 ± 19 kJ with Pla and Cit, respectively, P < 0.05). These variables were not altered by Arg supplementation (P > 0.05). In conclusion, these results suggest that short-term Cit, but not Arg, supplementation can improve blood pressure, V̇o2 kinetics, and exercise performance in healthy adults.
Abstract.
Author URL.
Black MI, Durant J, Jones AM, Vanhatalo A (2014). Critical power derived from a 3-min all-out test predicts 16.1-km road time-trial performance.
European Journal of Sport Science,
14(3), 217-223.
Abstract:
Critical power derived from a 3-min all-out test predicts 16.1-km road time-trial performance
It has been shown that the critical power (CP) in cycling estimated using a novel 3-min all-out protocol is reliable and closely matches the CP derived from conventional procedures. The purpose of this study was to assess the predictive validity of the all-out test CP estimate. We hypothesised that the all-out test CP would be significantly correlated with 16.1-km road time-trial (TT) performance and more strongly correlated with performance than the gas exchange threshold (GET), respiratory compensation point (RCP) and V̇O2 max. Ten club-level male cyclists (mean±SD: age 33.8±8.2 y, body mass 73.8±4.3 kg, V̇O2 max 60±4 ml·kg-1·min-1) performed a 10-mile road TT, a ramp incremental test to exhaustion, and two 3-min all-out tests, the first of which served as familiarisation. The 16.1-km TT performance (27.1±1.2 min) was significantly correlated with the CP (309±34 W; r=-0.83, P
Abstract.
Black MI, Durant J, Jones AM, Vanhatalo A (2014). Critical power derived from a 3-min all-out test predicts 16.1-km road time-trial performance.
Eur J Sport Sci,
14(3), 217-223.
Abstract:
Critical power derived from a 3-min all-out test predicts 16.1-km road time-trial performance.
It has been shown that the critical power (CP) in cycling estimated using a novel 3-min all-out protocol is reliable and closely matches the CP derived from conventional procedures. The purpose of this study was to assess the predictive validity of the all-out test CP estimate. We hypothesised that the all-out test CP would be significantly correlated with 16.1-km road time-trial (TT) performance and more strongly correlated with performance than the gas exchange threshold (GET), respiratory compensation point (RCP) and VO2 max. Ten club-level male cyclists (mean±SD: age 33.8±8.2 y, body mass 73.8±4.3 kg, VO2 max 60±4 ml·kg(-1)·min(-1)) performed a 10-mile road TT, a ramp incremental test to exhaustion, and two 3-min all-out tests, the first of which served as familiarisation. The 16.1-km TT performance (27.1±1.2 min) was significantly correlated with the CP (309±34 W; r = -0.83, P
Abstract.
Author URL.
Vanhatalo A, Jones AM, Blackwell JR, Winyard PG, Fulford J (2014). Dietary nitrate accelerates postexercise muscle metabolic recovery and O2 delivery in hypoxia.
J Appl Physiol (1985),
117(12), 1460-1470.
Abstract:
Dietary nitrate accelerates postexercise muscle metabolic recovery and O2 delivery in hypoxia.
We tested the hypothesis that the time constants (τ) of postexercise T2. MRI signal intensity (an index of O2 delivery) and muscle [PCr] (an index of metabolic perturbation, measured by (31)P-MRS) in hypoxia would be accelerated after dietary nitrate (NO3 (-)) supplementation. In a double-blind crossover design, eight moderately trained subjects underwent 5 days of NO3 (-) (beetroot juice, BR; 8.2 mmol/day NO3 (-)) and placebo (PL; 0.003 mmol/day NO3 (-)) supplementation in four conditions: normoxic PL (N-PL), hypoxic PL (H-PL; 13% O2), normoxic NO3 (-) (N-BR), and hypoxic NO3 (-) (H-BR). The single-leg knee-extension protocol consisted of 10 min of steady-state exercise and 24 s of high-intensity exercise. The [PCr] recovery τ was greater in H-PL (30 ± 4 s) than H-BR (22 ± 4 s), N-PL (24 ± 4 s) and N-BR (22 ± 4 s) (P < 0.05) and the maximal rate of mitochondrial ATP resynthesis (Qmax) was lower in the H-PL (1.12 ± 0.16 mM/s) compared with H-BR (1.35 ± 0.26 mM/s), N-PL (1.47 ± 0.28 mM/s), and N-BR (1.40 ± 0.21 mM/s) (P < 0.05). The τ of postexercise T2. signal intensity was greater in H-PL (47 ± 14 s) than H-BR (32 ± 10 s), N-PL (38 ± 9 s), and N-BR (27 ± 6 s) (P < 0.05). The postexercise [PCr] and T2. recovery τ were correlated in hypoxia (r = 0.60; P < 0.05), but not in normoxia (r = 0.28; P > 0.05). These findings suggest that the NO3 (-)-NO2 (-)-NO pathway is a significant modulator of muscle energetics and O2 delivery during hypoxic exercise and subsequent recovery.
Abstract.
Author URL.
Jones AM (2014). Dietary nitrate supplementation and exercise performance.
Sports Med,
44 Suppl 1(Suppl 1), S35-S45.
Abstract:
Dietary nitrate supplementation and exercise performance.
Dietary nitrate is growing in popularity as a sports nutrition supplement. This article reviews the evidence base for the potential of inorganic nitrate to enhance sports and exercise performance. Inorganic nitrate is present in numerous foodstuffs and is abundant in green leafy vegetables and beetroot. Following ingestion, nitrate is converted in the body to nitrite and stored and circulated in the blood. In conditions of low oxygen availability, nitrite can be converted into nitric oxide, which is known to play a number of important roles in vascular and metabolic control. Dietary nitrate supplementation increases plasma nitrite concentration and reduces resting blood pressure. Intriguingly, nitrate supplementation also reduces the oxygen cost of submaximal exercise and can, in some circumstances, enhance exercise tolerance and performance. The mechanisms that may be responsible for these effects are reviewed and practical guidelines for safe and efficacious dietary nitrate supplementation are provided.
Abstract.
Author URL.
Kelly J, Vanhatalo A, Bailey SJ, Wylie LJ, Tucker C, List S, Winyard PG, Jones AM (2014). Dietary nitrate supplementation: effects on plasma nitrite and pulmonary O2 uptake dynamics during exercise in hypoxia and normoxia.
Am J Physiol Regul Integr Comp Physiol,
307(7), R920-R930.
Abstract:
Dietary nitrate supplementation: effects on plasma nitrite and pulmonary O2 uptake dynamics during exercise in hypoxia and normoxia.
We investigated the effects of dietary nitrate (NO3 (-)) supplementation on the concentration of plasma nitrite ([NO2 (-)]), oxygen uptake (V̇o2) kinetics, and exercise tolerance in normoxia (N) and hypoxia (H). In a double-blind, crossover study, 12 healthy subjects completed cycle exercise tests, twice in N (20.9% O2) and twice in H (13.1% O2). Subjects ingested either 140 ml/day of NO3 (-)-rich beetroot juice (8.4 mmol NO3; BR) or NO3 (-)-depleted beetroot juice (PL) for 3 days prior to moderate-intensity and severe-intensity exercise tests in H and N. Preexercise plasma [NO2 (-)] was significantly elevated in H-BR and N-BR compared with H-PL (P < 0.01) and N-PL (P < 0.01). The rate of decline in plasma [NO2 (-)] was greater during severe-intensity exercise in H-BR [-30 ± 22 nM/min, 95% confidence interval (CI); -44, -16] compared with H-PL (-7 ± 10 nM/min, 95% CI; -13, -1; P < 0.01) and in N-BR (-26 ± 19 nM/min, 95% CI; -38, -14) compared with N-PL (-1 ± 6 nM/min, 95% CI; -5, 2; P < 0.01). During moderate-intensity exercise, steady-state pulmonary V̇o2 was lower in H-BR (1.91 ± 0.28 l/min, 95% CI; 1.77, 2.13) compared with H-PL (2.05 ± 0.25 l/min, 95% CI; 1.93, 2.26; P = 0.02), and V̇o2 kinetics was faster in H-BR (τ: 24 ± 13 s, 95% CI; 15, 32) compared with H-PL (31 ± 11 s, 95% CI; 23, 38; P = 0.04). NO3 (-) supplementation had no significant effect on V̇o2 kinetics during severe-intensity exercise in hypoxia, or during moderate-intensity or severe-intensity exercise in normoxia. Tolerance to severe-intensity exercise was improved by NO3 (-) in hypoxia (H-PL: 197 ± 28; 95% CI; 173, 220 vs. H-BR: 214 ± 43 s, 95% CI; 177, 249; P = 0.04) but not normoxia. The metabolism of NO2 (-) during exercise is altered by NO3 (-) supplementation, exercise, and to a lesser extent, hypoxia. In hypoxia, NO3 (-) supplementation enhances V̇o2 kinetics during moderate-intensity exercise and improves severe-intensity exercise tolerance. These findings may have important implications for individuals exercising at altitude.
Abstract.
Author URL.
Eston RG, Crockett A, Jones AM (2014). Discussion of "The efficacy of the self-paced V̇O2max test to measure maximal oxygen uptake in treadmill running".
Appl Physiol Nutr Metab,
39(5), 581-582.
Author URL.
Ferguson SK, Hirai DM, Copp SW, Holdsworth CT, Allen JD, Jones AM, Musch TI, Poole DC (2014). Dose dependent effects of nitrate supplementation on cardiovascular control and microvascular oxygenation dynamics in healthy rats.
Nitric Oxide,
39, 51-58.
Abstract:
Dose dependent effects of nitrate supplementation on cardiovascular control and microvascular oxygenation dynamics in healthy rats.
High dose nitrate (NO3(-)) supplementation via beetroot juice (BR, 1 mmol/kg/day) lowers mean arterial blood pressure (MAP) and improves skeletal muscle blood flow and O2 delivery/utilization matching thereby raising microvascular O2 pressure (PO2mv). We tested the hypothesis that a low dose of NO3(-) supplementation, consistent with a diet containing NO3(-) rich vegetables (BRLD, 0.3 mmol/kg/day), would be sufficient to cause these effects. Male Sprague-Dawley rats were administered a low dose of NO3(-) (0.3 mmol/kg/day; n=12), a high dose (1 mmol/kg/day; BRHD, n=6) or tap water (control, n=10) for 5 days. MAP, heart rate (HR), blood flow (radiolabeled microspheres) and vascular conductance (VC) were measured during submaximal treadmill exercise (20 m/min, 5% grade, equivalent to ~60% of maximal O2 uptake). Subsequently, PO2mv (phosphorescence quenching) was measured at rest and during 180 s of electrically-induced twitch contractions (1 Hz, ~6 V) of the surgically-exposed spinotrapezius muscle. BRLD and BRHD lowered resting (control: 139 ± 4, BRLD: 124 ± 5, BRHD: 128 ± 9 mmHg, P
Abstract.
Author URL.
Jones AM (2014). EJSS going forward apace.
Eur J Sport Sci,
14(1).
Author URL.
Skiba PF, Jackman S, Clarke D, Vanhatalo A, Jones AM (2014). Effect of work and recovery durations on W' reconstitution during intermittent exercise.
Med Sci Sports Exerc,
46(7), 1433-1440.
Abstract:
Effect of work and recovery durations on W' reconstitution during intermittent exercise.
PURPOSE: We recently presented an integrating model of the curvature constant of the hyperbolic power-time relationship (W') that permits the calculation of the W' balance (W'BAL) remaining at any time during intermittent exercise. Although a relationship between recovery power and the rate of W' recovery was demonstrated, the effect of the length of work or recovery intervals remains unclear. METHODS: After determining VO2max, critical power, and W', 11 subjects completed six separate exercise tests on a cycle ergometer on different days, and in random order. Tests consisted of a period of intermittent severe-intensity exercise until the subject depleted approximately 50% of their predicted W'BAL, followed by a constant work rate (CWR) exercise bout until exhaustion. Work rates were kept constant between trials; however, either work or recovery durations during intermittent exercise were varied. The actual W' measured during the CWR (W'ACT) was compared with the amount of W' predicted to be available by the W'BAL model. RESULTS: Although some differences between W'BAL and W'ACT were noted, these amounted to only -1.6 ± 1.1 kJ when averaged across all conditions. The W'ACT was linearly correlated with the difference between VO2 at the start of CWR and VO2max (r = 0.79, P < 0.01). CONCLUSIONS: the W'BAL model provided a generally robust prediction of CWR W'. There may exist a physiological optimum formulation of work and recovery intervals such that baseline VO2 can be minimized, leading to an enhancement of subsequent exercise tolerance. These results may have important implications for athletic training and racing.
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Author URL.
Skiba PF, Jackman S, Clarke D, Vanhatalo A, Jones AM (2014). Effect of work and recovery durations on W′ reconstitution during intermittent exercise.
Medicine and Science in Sports and Exercise,
46(7), 1433-1440.
Abstract:
Effect of work and recovery durations on W′ reconstitution during intermittent exercise
Purpose: We recently presented an integrating model of the curvature constant of the hyperbolic power-time relationship (W′) that permits the calculation of the W′ balance (W′BAL) remaining at any time during intermittent exercise. Although a relationship between recovery power and the rate of W′ recovery was demonstrated, the effect of the length of work or recovery intervals remains unclear. Methods: After determining V̇O2max, critical power, and W′, 11 subjects completed six separate exercise tests on a cycle ergometer on different days, and in random order. Tests consisted of a period of intermittent severe-intensity exercise until the subject depleted approximately 50% of their predicted W′BAL, followed by a constant work rate (CWR) exercise bout until exhaustion. Work rates were kept constant between trials; however, either work or recovery durations during intermittent exercise were varied. The actual W′ measured during the CWR (W′ACT) was compared with the amount of W′ predicted to be available by the W′BAL model. Results: Although some differences between W′BAL and W′ACT were noted, these amounted to only-1.6 ± 1.1 kJ when averaged across all conditions. The W′ACT was linearly correlated with the difference between V̇O2 at the start of CWR and V̇O2max (r = 0.79, P < 0.01). Conclusions: the W′BAL model provided a generally robust prediction of CWR W′. There may exist a physiological optimum formulation of work and recovery intervals such that baseline V̇O2 can be minimized, leading to an enhancement of subsequent exercise tolerance. These results may have important implications for athletic training and racing. © 2014 by the American College of Sports Medicine.
Abstract.
Da Boit M, Bailey SJ, Callow S, Dimenna FJ, Jones AM (2014). Effects of interval and continuous training on O2 uptake kinetics during severe-intensity exercise initiated from an elevated metabolic baseline.
J Appl Physiol (1985),
116(8), 1068-1077.
Abstract:
Effects of interval and continuous training on O2 uptake kinetics during severe-intensity exercise initiated from an elevated metabolic baseline.
The purpose of this study was to test the hypothesis that Vo2 kinetics would be speeded to a greater extent following repeated sprint training (RST), compared with continuous endurance training (ET), in the transition from moderate- to severe-intensity exercise. Twenty-three recreationally active subjects were randomly assigned to complete six sessions of ET (60-110 min of moderate-intensity cycling) or RST (four to seven 30-s all-out Wingate tests) over a 2-wk period. Subjects completed three identical work-to-work cycling exercise tests before and after the intervention period, consisting of baseline cycling at 20 W followed by sequential step increments to moderate- and severe-intensity work rates. The severe-intensity bout was continued to exhaustion on one occasion and was followed by a 60-s all-out sprint on another occasion. Phase II pulmonary Vo2 kinetics were speeded by a similar magnitude in both the lower (ET pre, 28 ± 4; ET post, 22 ± 4 s; RST pre, 25 ± 8; RST post, 20 ± 7 s) and upper (ET pre, 50 ± 10; ET post, 39 ± 11 s; RST pre, 54 ± 7; RST post, 40 ± 11 s) steps of the work-to-work test following ET and RST (P < 0.05). The tolerable duration of exercise and the total amount of sprint work completed in the exercise performance test were also similarly enhanced by ET and RST (P < 0.05). Therefore, ET and RST provoked comparable improvements in Vo2 kinetics and exercise performance in the transition from an elevated baseline work rate, with RST being a more time-efficient approach to elicit these adaptations.
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Author URL.
Holliss BA, Burden RJ, Jones AM, Pedlar CR (2014). Eight weeks of intermittent hypoxic training improves submaximal physiological variables in highly trained runners.
J Strength Cond Res,
28(8), 2195-2203.
Abstract:
Eight weeks of intermittent hypoxic training improves submaximal physiological variables in highly trained runners.
It is unclear whether intermittent hypoxic training (IHT) results in improvements in physiological variables associated with endurance running. Twelve highly trained runners (VO2peak 70.0 ± 3.5 ml·kg-1·min-1) performed incremental treadmill tests to exhaustion in normobaric normoxia and hypoxia (16.0% FIO2) to assess submaximal and maximal physiological variables and the limit of tolerance (T-Lim). Participants then completed 8 weeks of moderate to heavy intensity normoxic training (control [CONT]) or IHT (twice weekly 40 minutes runs, in combination with habitual training), in a single blinded manner, before repeating the treadmill tests. Submaximal heart rate decreased significantly more after IHT (-5 ± 5 b·min-1; p = 0.001) than after CONT ( -1 ± 5 b·min-1; p = 0.021). Changes in submaximal V[Combining Dot Above]O2 were significantly different between groups (p ≤ 0.05); decreasing in the IHT group in hypoxia (-2.6 ± 1.7 ml·kg-1·min-1; p = 0.001) and increasing in the CONT group in normoxia (+1.1 ± 2.1 ml·kg-1·min-1; p = 0.012). There were no VO2peak changes within either group, and while T-Lim improved post-IHT in hypoxia (p = 0.031), there were no significant differences between groups. Intermittent hypoxic training resulted in a degree of enhanced cardiovascular fitness that was evident during submaximal, but not maximal intensity exercise. These results suggest that moderate to heavy intensity IHT provides a mean of improving the capacity for submaximal exercise and may be useful for pre-acclimatization for subsequent exercise in hypoxia, but additional research is required to establish its efficacy for athletic performance at sea level.
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Author URL.
Black MI, Durant J, Jones AM, Vanhatalo A (2014). Erratum to Critical power derived from a 3-min all-out test predicts 16.1-km road time-trial performance (European Journal of Sport Science, (2013), 10.1080/17461391.2013.810306). European Journal of Sport Science, 14(3).
Hendricks S, Jones A (2014). European Journal of Sport Science gears up its social media. European Journal of Sport Science, 14(6), 519-520.
Wood MA, Bailey SJ, Jones AM (2014). Influence of all-out start duration on pulmonary oxygen uptake kinetics and high-intensity exercise performance.
J Strength Cond Res,
28(8), 2187-2194.
Abstract:
Influence of all-out start duration on pulmonary oxygen uptake kinetics and high-intensity exercise performance.
The purpose of this study was to investigate the influence of the duration of an "all-out" starting strategy on O2 uptake kinetics and performance during high-intensity exercise. Following familiarization, 9 recreationally active men completed three 1500-m cycling time trials (TT) using different pacing strategies. In a randomized order, subjects completed a self-paced TT (SPTT), or a TT that was self-paced following an initial 15-second (15TT) or 90-second (90TT) all-out sprint. VO2 was measured during all tests. The 1500-m TT completion time was faster in 15TT than SPTT (136.1 ± 6.2 seconds vs. 140.3 ± 7.1 seconds; p ≤ 0.05), but 90TT (138.5 ± 8.5 seconds) was not significantly different from either SPTT or 15TT (p > 0.05). The V[Combining Dot Above]O2 mean response time (MRT) was shorter in 15TT (27 ± 7 seconds) and 90TT (30 ± 9 seconds) than SPTT (40 ± 10 seconds; p ≤ 0.05), but the peak V[Combining Dot Above]O2 was only higher in 15TT (3.77 ± 0.42 L·min-1) compared with SPTT (3.47 ± 0.44 L·min-1) (p ≤ 0.05). There was a significant correlation (r = 0.77, p ≤ 0.05) between the shorter MRT and the faster 1500-m completion time for 15TT compared with SPTT. These results support the use of a brief (∼15 seconds) all-out start to improve performance in short-duration (
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Author URL.
Jones AM (2014). Influence of dietary nitrate on the physiological determinants of exercise performance: a critical review.
Appl Physiol Nutr Metab,
39(9), 1019-1028.
Abstract:
Influence of dietary nitrate on the physiological determinants of exercise performance: a critical review.
Dietary nitrate supplementation, usually in the form of beetroot juice, has been heralded as a possible new ergogenic aid for sport and exercise performance. Early studies in recreationally active participants indicated that nitrate ingestion significantly reduces the O2 cost of submaximal exercise and improves performance during high-intensity endurance exercise. Subsequent studies have begun to address the physiological mechanisms underpinning these observations and to investigate the human populations in whom, and the exercise conditions (high- vs. low-intensity, long- vs. short-duration, continuous vs. intermittent, normoxic vs. hypoxic) under which, nitrate supplementation may be beneficial. Moreover, the optimal nitrate loading regimen in terms of nitrate dose and duration of supplementation has been explored. Depending on these factors, nitrate supplementation has been shown to exert physiological effects that could be conducive to exercise performance enhancement, at least in recreationally active or sub-élite athletes. This article provides a "state-of-the-art" review of the literature pertinent to the evaluation of the efficacy of nitrate supplementation in altering the physiological determinants of sport and exercise performance.
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Thompson KG, Turner L, Prichard J, Dodd F, Kennedy DO, Haskell C, Blackwell JR, Jones AM (2014). Influence of dietary nitrate supplementation on physiological and cognitive responses to incremental cycle exercise.
Respir Physiol Neurobiol,
193, 11-20.
Abstract:
Influence of dietary nitrate supplementation on physiological and cognitive responses to incremental cycle exercise.
Dietary inorganic nitrate supplementation causes physiological effects which may enhance exercise tolerance. However it is not known whether nitrate might alter cognitive function during exercise. In a double-blind, cross-over study, sixteen subjects ingested either nitrate-rich beetroot juice or a placebo and completed a continuous cycle exercise test involving 20min stages at 50% and 70% V˙O2peak and a final stage at 90% V˙O2peak until volitional exhaustion. Cognitive tasks were completed before, during and after exercise. In the dietary nitrate condition: plasma [nitrite] increased (p
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Author URL.
Hoon MW, Hopkins WG, Jones AM, Martin DT, Halson SL, West NP, Johnson NA, Burke LM (2014). Nitrate supplementation and high-intensity performance in competitive cyclists.
Appl Physiol Nutr Metab,
39(9), 1043-1049.
Abstract:
Nitrate supplementation and high-intensity performance in competitive cyclists.
Consumption of inorganic nitrate (NO3(-)) is known to enhance endurance exercise performance in recreationally trained subjects. Here we report the effect on a high-intensity performance task in national-level cyclists. The performance test consisted of 2 cycle ergometer time trials of 4 min duration with 75 min between trials. In a randomized crossover design, 26 cyclists performed the test under the following 4 conditions (each separated by a 6-day washout): consumption of 70 mL of nitrate-rich beetroot juice at 150 min or 75 min before the first time trial, addition of a 35 mL "top-up dose" following the first time trial in the 150 min condition, and consumption of a placebo. A linear mixed model with adjustments for learning effects and athlete fitness (peak incremental power) was used to estimate effects on mean power, with probabilistic inferences based on a smallest important effect of 1.0%. Peak plasma nitrite (NO2(-)) concentration was greatest when nitrate was taken 75 min before the first time trial. Relative to placebo, the mean effect of all 3 nitrate treatments was unclear in the first time trial (1.3%, 90% confidence limits: ±1.7%), but possibly harmful in the second time trial (-0.3%, ±1.6%). Differences between nitrate treatments were unclear, as was the estimate of any consistent individual response to the treatments. Allowing for sampling uncertainty, the effect of nitrate on performance was less than previous studies. Under the conditions of our experiment, nitrate supplementation may be ineffective in facilitating high-intensity exercise in competitive athletes.
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Author URL.
Moore IS, Jones AM, Dixon SJ (2014). Relationship between metabolic cost and muscular coactivation across running speeds.
Journal of Science and Medicine in Sport,
17(6), 671-676.
Abstract:
Relationship between metabolic cost and muscular coactivation across running speeds
Objectives: Muscular coactivation can help stabilise a joint, but contrasting results in previous gait studies highlight that it is not clear whether this is metabolically beneficial. The aim was to assess the relationship between the metabolic cost of running and muscular coactivation across different running speeds, in addition to assessing the reliability and precision of lower limb muscular coactivation. Design: Eleven female recreational runners visited the laboratory on two separate occasions. On both occasions subjects ran at three speeds (9.1, 11 and 12kmh-1) for six minutes each. Methods: Oxygen consumption and electromyographic data were simultaneously recorded during the final two minutes of each speed. Temporal coactivations of lower limb muscles during the stance phase were calculated. Five muscles were assessed: rectus femoris, vastus lateralis, biceps femoris, tibialis anterior and gastrocnemius lateralis. Results: Nonparametric correlations revealed at least one significant, positive association between lower limb muscular coactivation and the metabolic cost of running for each speed. The length of tibialis anterior activation and muscular coactivation of the biceps femoris-tibialis anterior and gastrocnemius lateralis-tibialis anterior decreased with speed. Conclusions: These results show that longer coactivations of the proximal (rectus femoris-biceps femoris and vastus lateralis-biceps femoris) and leg extensor (rectus femoris-gastrocnemius lateralis) muscles were related to a greater metabolic cost of running, which could be detrimental to performance. The decrease in coactivation in the flexor and distal muscles at faster speeds occurs due to the shorter duration of tibialis anterior activation as speed increases, yet stability may be maintained.
Abstract.
Moore IS, Jones AM, Dixon SJ (2014). Relationship between metabolic cost and muscular coactivation across running speeds.
J Sci Med Sport,
17(6), 671-676.
Abstract:
Relationship between metabolic cost and muscular coactivation across running speeds.
OBJECTIVES: Muscular coactivation can help stabilise a joint, but contrasting results in previous gait studies highlight that it is not clear whether this is metabolically beneficial. The aim was to assess the relationship between the metabolic cost of running and muscular coactivation across different running speeds, in addition to assessing the reliability and precision of lower limb muscular coactivation. DESIGN: Eleven female recreational runners visited the laboratory on two separate occasions. On both occasions subjects ran at three speeds (9.1, 11 and 12 km h(-1)) for six minutes each. METHODS: Oxygen consumption and electromyographic data were simultaneously recorded during the final two minutes of each speed. Temporal coactivations of lower limb muscles during the stance phase were calculated. Five muscles were assessed: rectus femoris, vastus lateralis, biceps femoris, tibialis anterior and gastrocnemius lateralis. RESULTS: Nonparametric correlations revealed at least one significant, positive association between lower limb muscular coactivation and the metabolic cost of running for each speed. The length of tibialis anterior activation and muscular coactivation of the biceps femoris-tibialis anterior and gastrocnemius lateralis-tibialis anterior decreased with speed. CONCLUSIONS: These results show that longer coactivations of the proximal (rectus femoris-biceps femoris and vastus lateralis-biceps femoris) and leg extensor (rectus femoris-gastrocnemius lateralis) muscles were related to a greater metabolic cost of running, which could be detrimental to performance. The decrease in coactivation in the flexor and distal muscles at faster speeds occurs due to the shorter duration of tibialis anterior activation as speed increases, yet stability may be maintained.
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Author URL.
Lane SC, Hawley JA, Desbrow B, Jones AM, Blackwell JR, Ross ML, Zemski AJ, Burke LM (2014). Single and combined effects of beetroot juice and caffeine supplementation on cycling time trial performance.
Appl Physiol Nutr Metab,
39(9), 1050-1057.
Abstract:
Single and combined effects of beetroot juice and caffeine supplementation on cycling time trial performance.
Both caffeine and beetroot juice have ergogenic effects on endurance cycling performance. We investigated whether there is an additive effect of these supplements on the performance of a cycling time trial (TT) simulating the 2012 London Olympic Games course. Twelve male and 12 female competitive cyclists each completed 4 experimental trials in a double-blind Latin square design. Trials were undertaken with a caffeinated gum (CAFF) (3 mg·kg(-1) body mass (BM), 40 min prior to the TT), concentrated beetroot juice supplementation (BJ) (8.4 mmol of nitrate (NO3(-)), 2 h prior to the TT), caffeine plus beetroot juice (CAFF+BJ), or a control (CONT). Subjects completed the TT (females: 29.35 km; males: 43.83 km) on a laboratory cycle ergometer under conditions of best practice nutrition: following a carbohydrate-rich pre-event meal, with the ingestion of a carbohydrate-electrolyte drink and regular oral carbohydrate contact during the TT. Compared with CONT, power output was significantly enhanced after CAFF+BJ and CAFF (3.0% and 3.9%, respectively, p < 0.01). There was no effect of BJ supplementation when used alone (-0.4%, p = 0.6 compared with CONT) or when combined with caffeine (-0.9%, p = 0.4 compared with CAFF). We conclude that caffeine (3 mg·kg(-1) BM) administered in the form of a caffeinated gum increased cycling TT performance lasting ∼50-60 min by ∼3%-4% in both males and females. Beetroot juice supplementation was not ergogenic under the conditions of this study.
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Barker AR, Trebilcock E, Breese B, Jones AM, Armstrong N (2014). The effect of priming exercise on O2 uptake kinetics, muscle O2 delivery and utilization, muscle activity, and exercise tolerance in boys.
Appl Physiol Nutr Metab,
39(3), 308-317.
Abstract:
The effect of priming exercise on O2 uptake kinetics, muscle O2 delivery and utilization, muscle activity, and exercise tolerance in boys.
This study used priming exercise in young boys to investigate (i) how muscle oxygen delivery and oxygen utilization, and muscle activity modulate oxygen uptake kinetics during exercise; and (ii) whether the accelerated oxygen uptake kinetics following priming exercise can improve exercise tolerance. Seven boys that were aged 11.3 ± 1.6 years completed either a single bout (bout 1) or repeated bouts with 6 min of recovery (bout 2) of very heavy-intensity cycling exercise. During the tests oxygen uptake, muscle oxygenation, muscle electrical activity and exercise tolerance were measured. Priming exercise most likely shortened the oxygen uptake mean response time (change, ±90% confidence limits; -8.0 s, ±3.0), possibly increased the phase II oxygen uptake amplitude (0.11 L·min(-1), ±0.09) and very likely reduced the oxygen uptake slow component amplitude (-0.08 L·min(-1), ±0.07). Priming resulted in a likely reduction in integrated electromyography (-24% baseline, ±21% and -25% baseline, ±19) and a very likely reduction in Δ deoxyhaemoglobin/Δoxygen uptake (-0.16, ±0.11 and -0.09, ±0.05) over the phase II and slow component portions of the oxygen uptake response, respectively. A correlation was present between the change in tissue oxygenation index during bout 2 and the change in the phase II (r = -0.72, likely negative) and slow component (r = 0.72, likely positive) oxygen uptake amplitudes following priming exercise, but not for muscle activity. Exercise tolerance was likely reduced (change -177 s, ±180) following priming exercise. The altered phase II and slow component oxygen uptake amplitudes in boys following priming exercise are linked to an improved localised matching of muscle oxygen delivery to oxygen uptake and not muscle electrical activity. Despite more rapid oxygen uptake kinetics following priming exercise, exercise tolerance was not enhanced.
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Author URL.
Hoon MW, Jones AM, Johnson NA, Blackwell JR, Broad EM, Lundy B, Rice AJ, Burke LM (2014). The effect of variable doses of inorganic nitrate-rich beetroot juice on simulated 2,000-m rowing performance in trained athletes.
Int J Sports Physiol Perform,
9(4), 615-620.
Abstract:
The effect of variable doses of inorganic nitrate-rich beetroot juice on simulated 2,000-m rowing performance in trained athletes.
CONTEXT: Beetroot juice is a naturally rich source of inorganic nitrate (NO(3-)), a compound hypothesized to enhance endurance performance by improving exercise efficiency. PURPOSE: to investigate the effect of different doses of beetroot juice on 2000-m ergometer-rowing performance in highly trained athletes. METHODS: Ten highly trained male rowers volunteered to participate in a placebo-controlled, double-blinded crossover study. Two hours before undertaking a 2000-m rowing-ergometer test, subjects consumed beetroot juice containing 0 mmol (placebo), 4.2 mmol (SINGLE), or 8.4 mmol (DOUBLE) NO(3-). Blood samples were taken before supplement ingestion and immediately before the rowing test for analysis of plasma [NO(3-)] and [nitrite (NO(2-))]. RESULTS: the SINGLE dose demonstrated a trivial effect on time to complete 2000 m compared with placebo (mean difference: 0.2 ± 2.5 s). A possibly beneficial effect was found with DOUBLE compared with SINGLE (mean difference -1.8 ± 2.1 s) and with placebo (-1.6 ± 1.6 s). Plasma [NO(2-)] and [NO(3-)] demonstrated a dose-response effect, with greater amounts of ingested nitrate leading to substantially higher concentrations (DOUBLE > SINGLE > placebo). There was a moderate but insignificant correlation (r = -.593, P =. 055) between change in plasma [NO(2-)] and performance time. CONCLUSION: Compared with nitratedepleted beetroot juice, a high (8.4 mmol NO(3-)) but not moderate (4.2 mmol NO(3-)) dose of NO(3-) in beetroot juice, consumed 2 h before exercise, may improve 2000-m rowing performance in highly trained athletes.
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McNarry M, Jones A (2014). The influence of training status on the aerobic and anaerobic responses to exercise in children: a review.
European Journal of Sport Science,
14(SUPPL.1).
Abstract:
The influence of training status on the aerobic and anaerobic responses to exercise in children: a review
Exercise training represents a potent stimulus to the development of aerobic and anaerobic fitness in adults; whether the same is true in young children is unclear. With the possible exception of peak, many parameters of aerobic and anaerobic fitness remain scarcely investigated in children, especially pubertal children. Despite this lack of empirical evidence, it has been suggested that children may lack trainability and that this may be related to the presence of a maturational threshold below which significant adaptations to training cannot occur. This suggestion requires investigation, not least because the findings of some studies which appear to support this contention may in reality be a reflection of the use of an inappropriate test modality or training programme for the investigation of training status influences. The purpose of this review is therefore to provide insight into the current consensuses and controversies regarding the influence of training in young people. © 2014 Copyright European College of Sport Science.
Abstract.
Moore IS, Jones A, Dixon S (2014). The pursuit of improved running performance: can changes in cushioning and somatosensory feedback influence running economy and injury risk?.
Footwear Science,
6(1), 1-11.
Abstract:
The pursuit of improved running performance: can changes in cushioning and somatosensory feedback influence running economy and injury risk?
There is currently no consensus regarding the effect that barefoot (BFT) running has on running economy (RE). Stride length and shoe mass are confounding variables, with a BFT stride length being shorter than a shod (SH) stride length. Comparison of SH, minimalist shod (MS) and BFT allows controlled variation of cushioning and somatosensory feedback to determine the effect that either and/or both have on RE and running mechanics. Methods: Fifteen female habitually shod, recreational runners visited the laboratory twice. Familiarisation with BFT and SH treadmill running occurred during visit one, in addition to determining SH stride length and BFT stride length. During visit two participants ran BFT, SH and MS with BFT stride length and MS with SH stride length at 10 km·h-1 for six minutes with 10-minute rest periods between each condition. Lower limb kinematics, electromyography, impact acceleration and O2 were recorded during the final two minutes of each run. Results: BFT RE was significantly better than SH and MS with BFT stride length. SHRE was significantly worse than MS with SH stride length, but similar to MS with a BFT stride length. Low vertical oscillation, peak eversion and peak dorsiflexion, less plantarflexion at toe-off, in addition to an earlier occurrence of heel off, higher impact accelerations and greater tibialis anterior activity were observed during the most economical condition. Conclusions: Heightened somatosensory feedback and lack of cushioning (BFT) offered an advantage to economy over less somatosensory feedback (MS) and cushioning (SH). Whilst the low vertical oscillation and low plantarflexion at toe-off appear to contribute to the improved RE, other changes to running mechanics whilst BFT could potentially influence injury risk. © 2014 © 2014 Taylor & Francis.
Abstract.
Moore IS, Jones A, Dixon S (2014). The pursuit of improved running performance: can changes in cushioning and somatosensory feedback influence running economy and injury risk?. Footwear Science
Skiba PF, Clarke D, Vanhatalo A, Jones AM (2014). Validation of a novel intermittent w' model for cycling using field data.
Int J Sports Physiol Perform,
9(6), 900-904.
Abstract:
Validation of a novel intermittent w' model for cycling using field data.
Recently, an adaptation to the critical-power (CP) model was published, which permits the calculation of the balance of the work capacity available above the CP remaining (W'bal) at any time during intermittent exercise. As the model is now in use in both amateur and elite sport, the purpose of this investigation was to assess the validity of the W'bal model in the field. Data were collected from the bicycle power meters of 8 trained triathletes. W'bal was calculated and compared between files where subjects reported becoming prematurely exhausted during training or competition and files where the athletes successfully completed a difficult assigned task or race without becoming exhausted. Calculated W'bal was significantly different between the 2 conditions (P <. 0001). The mean W'bal at exhaustion was 0.5 ± 1.3 kJ (95% CI = 0-0.9 kJ), whereas the minimum W'bal in the nonexhausted condition was 3.6 ± 2.0 kJ (95% CI = 2.1-4.0 kJ). Receiver-operator-characteristic (ROC) curve analysis indicated that the W'bal model is useful for identifying the point at which athletes are in danger of becoming exhausted (area under the ROC curve =. 914, SE. 05, 95% CI. 82-1.0, P <. 0001). The W'bal model may therefore represent a useful new development in assessing athlete fatigue state during training and racing.
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Author URL.
Chidnok W, Dimenna FJ, Bailey SJ, Burnley M, Wilkerson DP, Vanhatalo A, Jones AM (2013).VO2max is not altered by self-pacing during incremental exercise.
Eur J Appl Physiol,
113(2), 529-539.
Abstract:
.VO2max is not altered by self-pacing during incremental exercise.
We tested the hypothesis that incremental cycling to exhaustion that is paced using clamps of the rating of perceived exertion (RPE) elicits higher. VO2max values compared to a conventional ramp incremental protocol when test duration is matched. Seven males completed three incremental tests to exhaustion to measure. VO2max. The incremental protocols were of similar duration and included: a ramp test at 30 W min(-1) with constant cadence (RAMP1); a ramp test at 30 W min(-1) with cadence free to fluctuate according to subject preference (RAMP2); and a self-paced incremental test in which the power output was selected by the subject according to prescribed increments in RPE (SPT). The subjects also completed a. VO2max 'verification' test at a fixed high-intensity power output and a 3-min all-out test. No difference was found for. VO2max between the incremental protocols (RAMP1 = 4.33 ± 0.60 L min(-1); RAMP2 = 4.31 ± 0.62 L min(-1); SPT = 4.36 ± 0.59 L min(-1); P > 0.05) nor between the incremental protocols and the peak.VO2max measured during the 3-min all-out test (4.33 ± 0.68 L min(-1)) or the. VO2max measured in the verification test (4.32 ± 0.69 L min(-1)). The integrated electromyogram, blood lactate concentration, heart rate and minute ventilation at exhaustion were not different (P > 0.05) between the incremental protocols. In conclusion, when test duration is matched, SPT does not elicit a higher. VO2max compared to conventional incremental protocols. The striking similarity of. VO2max measured across an array of exercise protocols indicates that there are physiological limits to the attainment of. VO2max that cannot be exceeded by self-pacing.
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Chidnok W, Dimenna FJ, Bailey SJ, Burnley M, Wilkerson DP, Vanhatalo A, Jones AM (2013).VO2max is not altered by self-pacing during incremental exercise: reply to the letter of Alexis R. Mauger.
Eur J Appl Physiol,
113(2), 543-544.
Author URL.
Mezzani A, Hamm LF, Jones AM, McBride PE, Moholdt T, Stone JA, Urhausen A, Williams MA (2013). Aerobic exercise intensity assessment and prescription in cardiac rehabilitation: a joint position statement of the European Association for Cardiovascular Prevention and Rehabilitation, the American Association of Cardiovascular and Pulmonary Rehabilitation and the Canadian Association of Cardiac Rehabilitation.
European Journal of Preventive Cardiology,
20(3), 442-467.
Abstract:
Aerobic exercise intensity assessment and prescription in cardiac rehabilitation: a joint position statement of the European Association for Cardiovascular Prevention and Rehabilitation, the American Association of Cardiovascular and Pulmonary Rehabilitation and the Canadian Association of Cardiac Rehabilitation
Aerobic exercise intensity prescription is a key issue in cardiac rehabilitation, being directly linked to both the amount of improvement in exercise capacity and the risk of adverse events during exercise. This joint position statement aims to provide professionals with up-to-date information regarding the identification of different exercise intensity domains, the methods of direct and indirect determination of exercise intensity for both continuous and interval aerobic training, the effects of the use of different exercise protocols on exercise intensity prescription and the indications for recommended exercise training prescription in specific cardiac patients' groups. The importance of functional evaluation through exercise testing prior to starting an aerobic training program is strongly emphasized, and ramp incremental cardiopulmonary exercise test, when available, is proposed as the gold standard for a physiologically comprehensive exercise intensity assessment and prescription. This may allow a shift from a 'range-based' to a 'threshold-based' aerobic exercise intensity prescription, which, combined with thorough clinical evaluation and exercise-related risk assessment, could maximize the benefits obtainable by the use of aerobic exercise training in cardiac rehabilitation. © the European Society of Cardiology 2012.
Abstract.
Mezzani A, Hamm LF, Jones AM, McBride PE, Moholdt T, Stone JA, Urhausen A, Williams MA, European Association for Cardiovascular Prevention and Rehabilitation, American Association of Cardiovascular and Pulmonary Rehabilitation, et al (2013). Aerobic exercise intensity assessment and prescription in cardiac rehabilitation: a joint position statement of the European Association for Cardiovascular Prevention and Rehabilitation, the American Association of Cardiovascular and Pulmonary Rehabilitation and the Canadian Association of Cardiac Rehabilitation.
Eur J Prev Cardiol,
20(3), 442-467.
Abstract:
Aerobic exercise intensity assessment and prescription in cardiac rehabilitation: a joint position statement of the European Association for Cardiovascular Prevention and Rehabilitation, the American Association of Cardiovascular and Pulmonary Rehabilitation and the Canadian Association of Cardiac Rehabilitation.
Aerobic exercise intensity prescription is a key issue in cardiac rehabilitation, being directly linked to both the amount of improvement in exercise capacity and the risk of adverse events during exercise. This joint position statement aims to provide professionals with up-to-date information regarding the identification of different exercise intensity domains, the methods of direct and indirect determination of exercise intensity for both continuous and interval aerobic training, the effects of the use of different exercise protocols on exercise intensity prescription and the indications for recommended exercise training prescription in specific cardiac patients' groups. The importance of functional evaluation through exercise testing prior to starting an aerobic training program is strongly emphasized, and ramp incremental cardiopulmonary exercise test, when available, is proposed as the gold standard for a physiologically comprehensive exercise intensity assessment and prescription. This may allow a shift from a 'range-based' to a 'threshold-based' aerobic exercise intensity prescription, which, combined with thorough clinical evaluation and exercise-related risk assessment, could maximize the benefits obtainable by the use of aerobic exercise training in cardiac rehabilitation.
Abstract.
Author URL.
Wylie LJ, Kelly J, Bailey SJ, Blackwell JR, Skiba PF, Winyard PG, Jeukendrup AE, Vanhatalo A, Jones AM (2013). Beetroot juice and exercise: pharmacodynamic and dose-response relationships.
J Appl Physiol (1985),
115(3), 325-336.
Abstract:
Beetroot juice and exercise: pharmacodynamic and dose-response relationships.
Dietary supplementation with beetroot juice (BR), containing approximately 5-8 mmol inorganic nitrate (NO3(-)), increases plasma nitrite concentration ([NO2(-)]), reduces blood pressure, and may positively influence the physiological responses to exercise. However, the dose-response relationship between the volume of BR ingested and the physiological effects invoked has not been investigated. In a balanced crossover design, 10 healthy men ingested 70, 140, or 280 ml concentrated BR (containing 4.2, 8.4, and 16.8 mmol NO3(-), respectively) or no supplement to establish the effects of BR on resting plasma [NO3(-)] and [NO2(-)] over 24 h. Subsequently, on six separate occasions, 10 subjects completed moderate-intensity and severe-intensity cycle exercise tests, 2.5 h postingestion of 70, 140, and 280 ml BR or NO3(-)-depleted BR as placebo (PL). Following acute BR ingestion, plasma [NO2(-)] increased in a dose-dependent manner, with the peak changes occurring at approximately 2-3 h. Compared with PL, 70 ml BR did not alter the physiological responses to exercise. However, 140 and 280 ml BR reduced the steady-state oxygen (O2) uptake during moderate-intensity exercise by 1.7% (P = 0.06) and 3.0% (P < 0.05), whereas time-to-task failure was extended by 14% and 12% (both P < 0.05), respectively, compared with PL. The results indicate that whereas plasma [NO2(-)] and the O2 cost of moderate-intensity exercise are altered dose dependently with NO3(-)-rich BR, there is no additional improvement in exercise tolerance after ingesting BR containing 16.8 compared with 8.4 mmol NO3(-). These findings have important implications for the use of BR to enhance cardiovascular health and exercise performance in young adults.
Abstract.
Author URL.
Breese BC, McNarry MA, Marwood S, Blackwell JR, Bailey SJ, Jones AM (2013). Beetroot juice supplementation speeds O2 uptake kinetics and improves exercise tolerance during severe-intensity exercise initiated from an elevated metabolic rate.
Am J Physiol Regul Integr Comp Physiol,
305(12), R1441-R1450.
Abstract:
Beetroot juice supplementation speeds O2 uptake kinetics and improves exercise tolerance during severe-intensity exercise initiated from an elevated metabolic rate.
Recent research has suggested that dietary nitrate (NO3(-)) supplementation might alter the physiological responses to exercise via specific effects on type II muscle. Severe-intensity exercise initiated from an elevated metabolic rate would be expected to enhance the proportional activation of higher-order (type II) muscle fibers. The purpose of this study was, therefore, to test the hypothesis that, compared with placebo (PL), NO3(-)-rich beetroot juice (BR) supplementation would speed the phase II VO2 kinetics (τ(p)) and enhance exercise tolerance during severe-intensity exercise initiated from a baseline of moderate-intensity exercise. Nine healthy, physically active subjects were assigned in a randomized, double-blind, crossover design to receive BR (140 ml/day, containing ~8 mmol of NO3(-)) and PL (140 ml/day, containing ~0.003 mmol of NO3(-)) for 6 days. On days 4, 5, and 6 of the supplementation periods, subjects completed a double-step exercise protocol that included transitions from unloaded to moderate-intensity exercise (U→M) followed immediately by moderate to severe-intensity exercise (M→S). Compared with PL, BR elevated resting plasma nitrite concentration (PL: 65 ± 32 vs. BR: 348 ± 170 nM, P < 0.01) and reduced the VO2 τ(p) in M→S (PL: 46 ± 13 vs. BR: 36 ± 10 s, P < 0.05) but not U→M (PL: 25 ± 4 vs. BR: 27 ± 6 s, P > 0.05). During M→S exercise, the faster VO2 kinetics coincided with faster near-infrared spectroscopy-derived muscle [deoxyhemoglobin] kinetics (τ; PL: 20 ± 9 vs. BR: 10 ± 3 s, P < 0.05) and a 22% greater time-to-task failure (PL: 521 ± 158 vs. BR: 635 ± 258 s, P < 0.05). Dietary supplementation with NO3(-)-rich BR juice speeds VO2 kinetics and enhances exercise tolerance during severe-intensity exercise when initiated from an elevated metabolic rate.
Abstract.
Author URL.
Wylie LJ, Mohr M, Krustrup P, Jackman SR, Ermιdis G, Kelly J, Black MI, Bailey SJ, Vanhatalo A, Jones AM, et al (2013). Dietary nitrate supplementation improves team sport-specific intense intermittent exercise performance.
European Journal of Applied Physiology,
113(7), 1673-1684.
Abstract:
Dietary nitrate supplementation improves team sport-specific intense intermittent exercise performance
Recent studies have suggested that dietary inorganic nitrate (NO 3- ) supplementation may improve muscle efficiency and endurance exercise tolerance but possible effects during team sport-specific intense intermittent exercise have not been examined. We hypothesized that NO 3- supplementation would enhance high-intensity intermittent exercise performance. Fourteen male recreational team-sport players were assigned in a double-blind, randomized, crossover design to consume 490 mL of concentrated, nitrate-rich beetroot juice (BR) and nitrate-depleted placebo juice (PL) over ∼30 h preceding the completion of a Yo-Yo intermittent recovery level 1 test (Yo-Yo IR1). Resting plasma nitrite concentration ([NO 2- ]) was ∼400 % greater in BR compared to PL. Plasma [NO 2- ] declined by 20 % in PL (P < 0.05) and by 54 % in BR (P < 0.05) from pre-exercise to end-exercise. Performance in the Yo-Yo IR1 was 4.2 % greater (P < 0.05) with BR (1,704 ± 304 m) compared to PL (1,636 ± 288 m). Blood [lactate] was not different between BR and PL, but the mean blood [glucose] was lower (3.8 ± 0.8 vs. 4.2 ± 1.1 mM, P < 0.05) and the rise in plasma [K + ] tended to be reduced in BR compared to PL (P = 0.08). These findings suggest that NO 3- supplementation may promote NO production via the nitrate-nitrite-NO pathway and enhance Yo-Yo IR1 test performance, perhaps by facilitating greater muscle glucose uptake or by better maintaining muscle excitability. Dietary NO 3- supplementation improves performance during intense intermittent exercise and may be a useful ergogenic aid for team sports players. © 2013 Springer-Verlag Berlin Heidelberg.
Abstract.
Wylie LJ, Mohr M, Krustrup P, Jackman SR, Ermιdis G, Kelly J, Black MI, Bailey SJ, Vanhatalo A, Jones AM, et al (2013). Dietary nitrate supplementation improves team sport-specific intense intermittent exercise performance.
Eur J Appl Physiol,
113(7), 1673-1684.
Abstract:
Dietary nitrate supplementation improves team sport-specific intense intermittent exercise performance.
Recent studies have suggested that dietary inorganic nitrate (NO₃(-)) supplementation may improve muscle efficiency and endurance exercise tolerance but possible effects during team sport-specific intense intermittent exercise have not been examined. We hypothesized that NO₃(-) supplementation would enhance high-intensity intermittent exercise performance. Fourteen male recreational team-sport players were assigned in a double-blind, randomized, crossover design to consume 490 mL of concentrated, nitrate-rich beetroot juice (BR) and nitrate-depleted placebo juice (PL) over ~30 h preceding the completion of a Yo-Yo intermittent recovery level 1 test (Yo-Yo IR1). Resting plasma nitrite concentration ([NO₂(-)]) was ~400% greater in BR compared to PL. Plasma [NO₂(-)] declined by 20% in PL (P < 0.05) and by 54 % in BR (P < 0.05) from pre-exercise to end-exercise. Performance in the Yo-Yo IR1 was 4.2% greater (P < 0.05) with BR (1,704 ± 304 m) compared to PL (1,636 ± 288 m). Blood [lactate] was not different between BR and PL, but the mean blood [glucose] was lower (3.8 ± 0.8 vs. 4.2 ± 1.1 mM, P < 0.05) and the rise in plasma [K(+)] tended to be reduced in BR compared to PL (P = 0.08). These findings suggest that NO₃(-) supplementation may promote NO production via the nitrate-nitrite-NO pathway and enhance Yo-Yo IR1 test performance, perhaps by facilitating greater muscle glucose uptake or by better maintaining muscle excitability. Dietary NO₃(-) supplementation improves performance during intense intermittent exercise and may be a useful ergogenic aid for team sports players.
Abstract.
Author URL.
Hoon M, Jones A, Johnson N, Blackwell J, Broad E, Lundy B, Rice A, Burke L (2013). Dose response of nitrate supplementation on 2000m rowing ergometer performance. Journal of Science and Medicine in Sport, 16, e35-e36.
Kelly J, Vanhatalo A, Wilkerson DP, Wylie LJ, Jones AM (2013). Effects of nitrate on the power-duration relationship for severe-intensity exercise.
Medicine and Science in Sports and Exercise,
45(9), 1798-1806.
Abstract:
Effects of nitrate on the power-duration relationship for severe-intensity exercise
PURPOSE: the power asymptote (critical power [CP]) and curvature constant (W′) of the power-duration relationship dictate the tolerance to severe-intensity exercise. We tested the hypothesis that dietary nitrate supplementation would increase the CP and/or the W′ during cycling exercise. METHODS: in a double-blind, randomized, crossover study, nine recreationally active male subjects supplemented their diet with either nitrate-rich concentrated beetroot juice (BR; 2 × 250 mL·d, ∼8.2 mmol·d nitrate) or a nitrate-depleted BR placebo (PL; 2 × 250 mL·d, ∼0.006 mmol·d nitrate). In each condition, the subjects completed four separate severe-intensity exercise bouts to exhaustion at 60% of the difference between the gas exchange threshold and the peak power attained during incremental exercise (60% Δ), 70% Δ, 80% Δ, and 100% peak power, and the results were used to establish CP and W′. RESULTS: Nitrate supplementation improved exercise tolerance during exercise at 60% Δ (BR, 696 ± 120 vs PL, 593 ± 68 s; P < 0.05), 70% Δ (BR, 452 ± 106 vs PL, 390 ± 86 s; P < 0.05), and 80% Δ (BR, 294 ± 50 vs PL, 263 ± 50 s; P < 0.05) but not 100% peak power (BR, 182 ± 37 vs PL, 166 ± 26 s; P = 0.10). Neither CP (BR, 221 ± 27 vs PL, 218 ± 26 W) nor W′ (BR, 19.3 ± 4.6 vs PL, 17.8 ± 3 kJ) were significantly altered by BR. CONCLUSION: Dietary nitrate supplementation improved endurance during severe-intensity exercise in recreationally active subjects without significantly increasing either the CP or the W′. Copyright © 2013 by the American College of Sports Medicine.
Abstract.
Kelly J, Vanhatalo A, Wilkerson DP, Wylie LJ, Jones AM (2013). Effects of nitrate on the power-duration relationship for severe-intensity exercise.
Med Sci Sports Exerc,
45(9), 1798-1806.
Abstract:
Effects of nitrate on the power-duration relationship for severe-intensity exercise.
PURPOSE: the power asymptote (critical power [CP]) and curvature constant (W') of the power-duration relationship dictate the tolerance to severe-intensity exercise. We tested the hypothesis that dietary nitrate supplementation would increase the CP and/or the W' during cycling exercise. METHODS: in a double-blind, randomized, crossover study, nine recreationally active male subjects supplemented their diet with either nitrate-rich concentrated beetroot juice (BR; 2 × 250 mL·d, ∼8.2 mmol·d nitrate) or a nitrate-depleted BR placebo (PL; 2 × 250 mL·d, ∼0.006 mmol·d nitrate). In each condition, the subjects completed four separate severe-intensity exercise bouts to exhaustion at 60% of the difference between the gas exchange threshold and the peak power attained during incremental exercise (60% Δ), 70% Δ, 80% Δ, and 100% peak power, and the results were used to establish CP and W'. RESULTS: Nitrate supplementation improved exercise tolerance during exercise at 60% Δ (BR, 696 ± 120 vs PL, 593 ± 68 s; P < 0.05), 70% Δ (BR, 452 ± 106 vs PL, 390 ± 86 s; P < 0.05), and 80% Δ (BR, 294 ± 50 vs PL, 263 ± 50 s; P < 0.05) but not 100% peak power (BR, 182 ± 37 vs PL, 166 ± 26 s; P = 0.10). Neither CP (BR, 221 ± 27 vs PL, 218 ± 26 W) nor W' (BR, 19.3 ± 4.6 vs PL, 17.8 ± 3 kJ) were significantly altered by BR. CONCLUSION: Dietary nitrate supplementation improved endurance during severe-intensity exercise in recreationally active subjects without significantly increasing either the CP or the W'.
Abstract.
Author URL.
Ferguson SK, Hirai DM, Copp SW, Holdsworth CT, Allen JD, Jones AM, Musch TI, Poole DC (2013). Effects of nitrate supplementation via beetroot juice on contracting rat skeletal muscle microvascular oxygen pressure dynamics.
Respir Physiol Neurobiol,
187(3), 250-255.
Abstract:
Effects of nitrate supplementation via beetroot juice on contracting rat skeletal muscle microvascular oxygen pressure dynamics.
NO3(-) supplementation via beetroot juice (BR) augments exercising skeletal muscle blood flow subsequent to its reduction to NO2(-) then NO. We tested the hypothesis that enhanced vascular control following BR would elevate the skeletal muscle O2 delivery/O2 utilization ratio (microvascular PO2, PmvO2) and raise the PmvO2 during the rest-contractions transition. Rats were administered BR (~0.8 mmol/kg/day, n=10) or water (control, n=10) for 5 days. PmvO2 was measured during 180 s of electrically induced (1 Hz) twitch spinotrapezius muscle contractions. There were no changes in resting or contracting steady-state PmvO2. However, BR slowed the PmvO2 fall following contractions onset such that time to reach 63% of the initial PmvO2 fall increased (MRT1; control: 16.8±1.9, BR: 24.4±2.7 s, p
Abstract.
Author URL.
Chidnok W, Dimenna FJ, Bailey SJ, Wilkerson DP, Vanhatalo A, Jones AM (2013). Effects of pacing strategy on work done above critical power during high-intensity exercise.
Medicine and Science in Sports and Exercise,
45(7), 1377-1385.
Abstract:
Effects of pacing strategy on work done above critical power during high-intensity exercise
PURPOSE: We investigated the influence of pacing strategy on the work completed above critical power (CP) before exhaustion (W>CP) and the peak V̇O2 attained during high-intensity cycling. METHODS: After the determination of V̇O2max from a ramp incremental cycling (INC) test and the estimation of the parameters of the power-duration relationship for high-intensity exercise (i.e. CP and W′) from a 3-min all-out cycling test (AOT), eight male subjects completed a cycle test to exhaustion at a severe-intensity constant work rate (CWR) estimated to result in exhaustion in 3 min and a self-paced 3-min cycling time trial (SPT). RESULTS: the V̇O 2max determined from INC was 4.24 ± 0.69 L·min -1, and the CP and the W′ estimated from AOT were 260 ± 60 W and 16.5 ± 4.0 kJ, respectively. W>CP during SPT was not significantly different from W>CP during CWR (15.3 ± 5.6 and 16.6 ± 7.4 kJ, respectively), and these values were also similar to W>CP during INC (16.4 ± 4.0 kJ) and W′ estimated from AOT. The peak V̇O2 during SPT was not significantly different from peak V̇O2 during CWR (4.20 ± 0.77 and 4.14 ± 0.75 L·min -1, respectively), and these values were similar to the V̇O 2max determined from INC and the peak V̇O2 during AOT (4.10 ± 0.79 L·min-1). CONCLUSION: Exhaustion during high-intensity exercise coincides with the achievement of the same peak V̇O2 (V̇O2max) and the completion of the same W>CP, irrespective of the work rate forcing function (INC or CWR) or pacing strategy (enforced pace or self-paced). These findings indicate that exhaustion during high-intensity exercise is based on highly predictable physiological processes, which are unaffected when pacing strategy is self-selected. Copyright © 2013 by the American College of Sports Medicine.
Abstract.
Chidnok W, Dimenna FJ, Bailey SJ, Wilkerson DP, Vanhatalo A, Jones AM (2013). Effects of pacing strategy on work done above critical power during high-intensity exercise.
Med Sci Sports Exerc,
45(7), 1377-1385.
Abstract:
Effects of pacing strategy on work done above critical power during high-intensity exercise.
PURPOSE: We investigated the influence of pacing strategy on the work completed above critical power (CP) before exhaustion (W>CP) and the peak V˙O2 attained during high-intensity cycling. METHODS: After the determination of VO(2max) from a ramp incremental cycling (INC) test and the estimation of the parameters of the power-duration relationship for high-intensity exercise (i.e. CP and W') from a 3-min all-out cycling test (AOT), eight male subjects completed a cycle test to exhaustion at a severe-intensity constant work rate (CWR) estimated to result in exhaustion in 3 min and a self-paced 3-min cycling time trial (SPT). RESULTS: the VO(2max) determined from INC was 4.24 ± 0.69 L · min(-1), and the CP and the W' estimated from AOT were 260 ± 60 W and 16.5 ± 4.0 kJ, respectively. W>CP during SPT was not significantly different from W>CP during CWR (15.3 ± 5.6 and 16.6 ± 7.4 kJ, respectively), and these values were also similar to W(>CP) during INC (16.4 ± 4.0 kJ) and W' estimated from AOT. The peak VO(2) during SPT was not significantly different from peak VO(2) during CWR (4.20 ± 0.77 and 4.14 ± 0.75 L · min(-1), respectively), and these values were similar to the VO(2max) determined from INC and the peak VO(2) during AOT (4.10 ± 0.79 L · min(-1)). CONCLUSION: Exhaustion during high-intensity exercise coincides with the achievement of the same peak VO2 (VO(2max)) and the completion of the same W>CP, irrespective of the work rate forcing function (INC or CWR) or pacing strategy (enforced pace or self-paced). These findings indicate that exhaustion during high-intensity exercise is based on highly predictable physiological processes, which are unaffected when pacing strategy is self-selected.
Abstract.
Author URL.
Kelly J, Fulford J, Vanhatalo A, Blackwell JR, French O, Bailey SJ, Gilchrist M, Winyard PG, Jones AM (2013). Effects of short-term dietary nitrate supplementation on blood pressure, O2 uptake kinetics, and muscle and cognitive function in older adults.
Am J Physiol Regul Integr Comp Physiol,
304(2), R73-R83.
Abstract:
Effects of short-term dietary nitrate supplementation on blood pressure, O2 uptake kinetics, and muscle and cognitive function in older adults.
Dietary nitrate (NO(3)(-)) supplementation has been shown to reduce resting blood pressure and alter the physiological response to exercise in young adults. We investigated whether these effects might also be evident in older adults. In a double-blind, randomized, crossover study, 12 healthy, older (60-70 yr) adults supplemented their diet for 3 days with either nitrate-rich concentrated beetroot juice (BR; 2 × 70 ml/day, ∼9.6 mmol/day NO(3)(-)) or a nitrate-depleted beetroot juice placebo (PL; 2 × 70 ml/day, ∼0.01 mmol/day NO(3)(-)). Before and after the intervention periods, resting blood pressure and plasma [nitrite] were measured, and subjects completed a battery of physiological and cognitive tests. Nitrate supplementation significantly increased plasma [nitrite] and reduced resting systolic (BR: 115 ± 9 vs. PL: 120 ± 6 mmHg; P < 0.05) and diastolic (BR: 70 ± 5 vs. PL: 73 ± 5 mmHg; P < 0.05) blood pressure. Nitrate supplementation resulted in a speeding of the Vo(2) mean response time (BR: 25 ± 7 vs. PL: 28 ± 7 s; P < 0.05) in the transition from standing rest to treadmill walking, although in contrast to our hypothesis, the O(2) cost of exercise remained unchanged. Functional capacity (6-min walk test), the muscle metabolic response to low-intensity exercise, brain metabolite concentrations, and cognitive function were also not altered. Dietary nitrate supplementation reduced resting blood pressure and improved Vo(2) kinetics during treadmill walking in healthy older adults but did not improve walking or cognitive performance. These results may have implications for the enhancement of cardiovascular health in older age.
Abstract.
Author URL.
Ferguson SK, Hirai DM, Copp SW, Holdsworth CT, Allen JD, Jones AM, Musch TI, Poole DC (2013). Impact of dietary nitrate supplementation via beetroot juice on exercising muscle vascular control in rats.
J Physiol,
591(2), 547-557.
Abstract:
Impact of dietary nitrate supplementation via beetroot juice on exercising muscle vascular control in rats.
Dietary nitrate (NO(3)(-)) supplementation, via its reduction to nitrite (NO(2)(-)) and subsequent conversion to nitric oxide (NO) and other reactive nitrogen intermediates, reduces blood pressure and the O(2) cost of submaximal exercise in humans. Despite these observations, the effects of dietary NO(3)(-) supplementation on skeletal muscle vascular control during locomotory exercise remain unknown. We tested the hypotheses that dietary NO(3)(-) supplementation via beetroot juice (BR) would reduce mean arterial pressure (MAP) and increase hindlimb muscle blood flow in the exercising rat. Male Sprague-Dawley rats (3-6 months) were administered either NO(3)(-) (via beetroot juice; 1 mmol kg(-1) day(-1), BR n = 8) or untreated (control, n = 11) tap water for 5 days. MAP and hindlimb skeletal muscle blood flow and vascular conductance (radiolabelled microsphere infusions) were measured during submaximal treadmill running (20 m min(-1), 5% grade). BR resulted in significantly lower exercising MAP (control: 137 ± 3, BR: 127 ± 4 mmHg, P < 0.05) and blood [lactate] (control: 2.6 ± 0.3, BR: 1.9 ± 0.2 mm, P < 0.05) compared to control. Total exercising hindlimb skeletal muscle blood flow (control: 108 ± 8, BR: 150 ± 11 ml min(-1) (100 g)(-1), P < 0.05) and vascular conductance (control: 0.78 ± 0.05, BR: 1.16 ± 0.10 ml min(-1) (100 g)(-1) mmHg(-1), P < 0.05) were greater in rats that received BR compared to control. The relative differences in blood flow and vascular conductance for the 28 individual hindlimb muscles and muscle parts correlated positively with their percentage type IIb + d/x muscle fibres (blood flow: r = 0.74, vascular conductance: r = 0.71, P < 0.01 for both). These data support the hypothesis that NO(3)(-) supplementation improves vascular control and elevates skeletal muscle O(2) delivery during exercise predominantly in fast-twitch type II muscles, and provide a potential mechanism by which NO(3)(-) supplementation improves metabolic control.
Abstract.
Author URL.
Ingham SA, Fudge BW, Pringle JS, Jones AM (2013). Improvement of 800-m Running Performance with Prior High-Intensity Exercise.
Int J Sports Physiol Perform,
8(1), 77-83.
Abstract:
Improvement of 800-m Running Performance with Prior High-Intensity Exercise.
Prior high-intensity exercise increases the oxidative energy contribution to subsequent exercise and may enhance exercise tolerance. The potential impact of a high-intensity warm-up on competitive performance, however, has not been investigated.
Abstract.
Ingham SA, Fudge BW, Pringle JS, Jones AM (2013). Improvement of 800-m running performance with prior high-intensity exercise.
Int J Sports Physiol Perform,
8(1), 77-83.
Abstract:
Improvement of 800-m running performance with prior high-intensity exercise.
UNLABELLED: Prior high-intensity exercise increases the oxidative energy contribution to subsequent exercise and may enhance exercise tolerance. The potential impact of a high-intensity warm-up on competitive performance, however, has not been investigated. PURPOSE: to test the hypothesis that a high-intensity warm-up would speed VO2 kinetics and enhance 800-m running performance in well-trained athletes. METHODS: Eleven highly trained middle-distance runners completed two 800-m time trials on separate days on an indoor track, preceded by 2 different warm-up procedures. The 800-m time trials were preceded by a 10-min self-paced jog and standardized mobility drills, followed by either 6 × 50-m strides (control [CON]) or 2 × 50-m strides and a continuous high-intensity 200-m run (HWU) at race pace. Blood [La] was measured before the time trials, and VO2 was measured breath by breath throughout exercise. RESULTS: 800-m time-trial performance was significantly faster after HWU (124.5 ± 8.3 vs CON, 125.7 ± 8.7 s, P <. 05). Blood [La] was greater after HWU (3.6 ± 1.9 vs CON, 1.7 ± 0.8 mM; P <. 01). The mean response time for VO2 was not different between conditions (HWU, 27 ± 6 vs CON, 28 ± 7 s), but total O2 consumed (HWU, 119 ± 18 vs CON, 109 ± 28 ml/kg, P =. 05) and peak VO2 attained (HWU, 4.21 ± 0.85 vs CON, 3.91 ± 0.63 L/min; P =. 08) tended to be greater after HWU. CONCLUSIONS: These data indicate that a sustained high-intensity warm-up enhances 800-m time-trial performance in trained athletes.
Abstract.
Author URL.
Jones AM, Vanhatalo A, Bailey SJ (2013). Influence of dietary nitrate supplementation on exercise tolerance and performance.
Nestle Nutr Inst Workshop Ser,
75, 27-40.
Abstract:
Influence of dietary nitrate supplementation on exercise tolerance and performance.
Several recent studies indicate that supplementation of the diet with inorganic nitrate results in a significant reduction in pulmonary O2 uptake during sub-maximal exercise, an effect that appears to be related to enhanced skeletal muscle efficiency. The physiological mechanisms responsible for this effect are not completely understood but are presumably linked to the bioconversion of ingested nitrate into nitrite and thence to nitric oxide. Nitrite and/or nitric oxide may influence muscle contractile efficiency perhaps via effects on sarcoplasmic reticulum calcium handling or actin-myosin interaction, and may also improve the efficiency of mitochondrial oxidative phosphorylation. A reduced O2 cost of exercise can be observed within 3 h of the consumption of 5-6 mmol of nitrate, and this effect can be preserved for at least 15 days provided that the same 'dose' of nitrate is consumed daily. A reduced O2 cost of exercise following nitrate supplementation has now been reported for several types of exercise including cycling, walking, running, and knee extension exercise. Dietary nitrate supplementation has been reported to extend the time to exhaustion during high-intensity constant work rate exercise by 16-25% and to enhance cycling performance over 4, 10, and 16.1 km by 1-2% in recreationally active and moderately trained subjects. Although nitrate appears to be a promising 'new' ergogenic aid, additional research is required to determine the scope of its effects in different populations and different types of exercise.
Abstract.
Author URL.
Fulford J, Winyard PG, Vanhatalo A, Bailey SJ, Blackwell JR, Jones AM (2013). Influence of dietary nitrate supplementation on human skeletal muscle metabolism and force production during maximum voluntary contractions.
Pflugers Archiv European Journal of Physiology,
465(4), 517-528.
Abstract:
Influence of dietary nitrate supplementation on human skeletal muscle metabolism and force production during maximum voluntary contractions
Dietary nitrate supplementation, which enhances nitric oxide (NO) bioavailability, has previously been shown to contribute to improved exercise performance by reducing both oxygen cost and energy expenditure. In contrast, previous studies have indicated that NO can lower force production in vitro. To examine the role of dietary nitrates in regulating force generation under normal physiological conditions, we undertook an extended nitrate supplementation regime and determined force output and energy cost with a repeated isometric maximum voluntary contraction (MVC) protocol. In a double-blind, randomized, crossover design, eight participants received 0.5 l/day of nitrate-rich (BR) or nitrate-depleted (PL) beetroot juice for 15 days and completed an exercise protocol consisting of 50 MVCs at 2.5 h, 5 days and 15 days after the beginning of the supplementation period. No significant reduction in force output was determined for BR relative to PL for the peak contraction, the mean or the end force, and no significant time effect was found over the course of the supplementation period. There was a reduction in the mean PCr cost of exercise averaged over the BR supplementation trials, but this did not reach statistical significance for end exercise (BR 15.10 ± 4.14 mM, PL 17.10 ± 5.34 mM, P = 0.06) or the mean throughout the protocol (BR 15.96 ± 4.14 mM, PL 17.79 ± 4.51 mM, P = 0.06). However, a significant reduction in PCr cost per unit force output was found for BR at end exercise (P = 0.04). These results indicate that, under normal physiological conditions, increased NO bioavailability is not associated with a reduction of force-generating capability in human skeletal muscle and confirm that nitrate supplementation reduces the PCr cost of force production. © 2013 Springer-Verlag Berlin Heidelberg.
Abstract.
Fulford J, Winyard PG, Vanhatalo A, Bailey SJ, Blackwell JR, Jones AM (2013). Influence of dietary nitrate supplementation on human skeletal muscle metabolism and force production during maximum voluntary contractions.
Pflugers Arch,
465(4), 517-528.
Abstract:
Influence of dietary nitrate supplementation on human skeletal muscle metabolism and force production during maximum voluntary contractions.
Dietary nitrate supplementation, which enhances nitric oxide (NO) bioavailability, has previously been shown to contribute to improved exercise performance by reducing both oxygen cost and energy expenditure. In contrast, previous studies have indicated that NO can lower force production in vitro. To examine the role of dietary nitrates in regulating force generation under normal physiological conditions, we undertook an extended nitrate supplementation regime and determined force output and energy cost with a repeated isometric maximum voluntary contraction (MVC) protocol. In a double-blind, randomized, crossover design, eight participants received 0.5 l/day of nitrate-rich (BR) or nitrate-depleted (PL) beetroot juice for 15 days and completed an exercise protocol consisting of 50 MVCs at 2.5 h, 5 days and 15 days after the beginning of the supplementation period. No significant reduction in force output was determined for BR relative to PL for the peak contraction, the mean or the end force, and no significant time effect was found over the course of the supplementation period. There was a reduction in the mean PCr cost of exercise averaged over the BR supplementation trials, but this did not reach statistical significance for end exercise (BR 15.10 ± 4.14 mM, PL 17.10 ± 5.34 mM, P = 0.06) or the mean throughout the protocol (BR 15.96 ± 4.14 mM, PL 17.79 ± 4.51 mM, P = 0.06). However, a significant reduction in PCr cost per unit force output was found for BR at end exercise (P = 0.04). These results indicate that, under normal physiological conditions, increased NO bioavailability is not associated with a reduction of force-generating capability in human skeletal muscle and confirm that nitrate supplementation reduces the PCr cost of force production.
Abstract.
Author URL.
Holliss BA, Fulford J, Vanhatalo A, Pedlar CR, Jones AM (2013). Influence of intermittent hypoxic training on muscle energetics and exercise tolerance.
J Appl Physiol (1985),
114(5), 611-619.
Abstract:
Influence of intermittent hypoxic training on muscle energetics and exercise tolerance.
Intermittent hypoxic training (IHT) is sometimes used by athletes to enhance nonhematological physiological adaptations to simulated altitude. We investigated whether IHT would result in greater improvements in muscle energetics and exercise tolerance compared with work-matched intermittent normoxic training (INT). Nine physically active men completed 3 wk of intensive, single-leg knee-extensor exercise training. Each training session consisted of 25 min of IHT (FiO2 14.5 ± 0.1%) with the experimental leg and 25 min of INT with the alternate leg, which served as a control. Before and after the training intervention, subjects completed a test protocol consisting of a bout of submaximal constant-work-rate exercise, a 24-s high-intensity exercise bout to quantify the phosphocreatine recovery time constant ([PCr]-τ), and an incremental test to the limit of tolerance. The tests were completed in normoxia and hypoxia in both INT and IHT legs. Muscle metabolism was assessed noninvasively using (31)P-magnetic resonance spectroscopy. Improvements in the time-to-exhaustion during incremental exercise were not significantly different between training conditions either in normoxia (INT, 28 ± 20% vs. IHT, 25 ± 9%; P = 0.86) or hypoxia (INT, 21 ± 10% vs. IHT, 15 ± 11%; P = 0.29). In hypoxia, [PCr]-τ was speeded slightly but significantly more post-IHT compared with post-INT (-7.3 ± 2.9 s vs. -3.7 ± 1.7 s; P < 0.01), but changes in muscle metabolite concentrations during exercise were essentially not different between IHT and INT. Under the conditions of this investigation, IHT does not appreciably alter muscle metabolic responses or incremental exercise performance compared with INT.
Abstract.
Author URL.
Chidnok W, Fulford J, Bailey SJ, Dimenna FJ, Skiba PF, Vanhatalo A, Jones AM (2013). Muscle metabolic determinants of exercise tolerance following exhaustion: relationship to the "critical power".
J Appl Physiol (1985),
115(2), 243-250.
Abstract:
Muscle metabolic determinants of exercise tolerance following exhaustion: relationship to the "critical power".
We tested the hypothesis that muscle high-energy phosphate compounds and metabolites related to the fatigue process would be recovered after exhaustion during recovery exercise performed below but not above critical power (CP) and that these changes would influence the capacity to continue exercise. Eight male subjects completed single-leg, knee-extension exercise to exhaustion (for ∼180 s) on three occasions, followed by a work-rate reduction to severe-intensity exercise, heavy-intensity exercise (CP differ according to whether the recovery exercise is performed below or above the CP. These findings confirm the importance of the CP as an intramuscular metabolic threshold that dictates the accumulation of fatigue-related metabolites and the capacity to tolerate high-intensity exercise.
Abstract.
Author URL.
Chidnok W, DiMenna FJ, Fulford J, Bailey SJ, Skiba PF, Vanhatalo A, Jones AM (2013). Muscle metabolic responses during high-intensity intermittent exercise measured by (31)P-MRS: relationship to the critical power concept.
Am J Physiol Regul Integr Comp Physiol,
305(9), R1085-R1092.
Abstract:
Muscle metabolic responses during high-intensity intermittent exercise measured by (31)P-MRS: relationship to the critical power concept.
We investigated the responses of intramuscular phosphate-linked metabolites and pH (as assessed by (31)P-MRS) during intermittent high-intensity exercise protocols performed with different recovery-interval durations. Following estimation of the parameters of the power-duration relationship, i.e. the critical power (CP) and curvature constant (W'), for severe-intensity constant-power exercise, nine male subjects completed three intermittent exercise protocols to exhaustion where periods of high-intensity constant-power exercise (60 s) were separated by different durations of passive recovery (18 s, 30 s and 48 s). The tolerable duration of exercise was 304 ± 68 s, 516 ± 142 s, and 847 ± 240 s for the 18-s, 30-s, and 48-s recovery protocols, respectively (P < 0.05). The work done >CP (W>CP) was significantly greater for all intermittent protocols compared with the subjects' W', and this difference became progressively greater as recovery-interval duration was increased. The restoration of intramuscular phosphocreatine concentration during recovery was greatest, intermediate, and least for 48 s, 30 s, and 18 s of recovery, respectively (P < 0.05). The W>CP in excess of W' increased with greater durations of recovery, and this was correlated with the mean magnitude of muscle phosphocreatine reconstitution between work intervals (r = 0.61; P < 0.01). The results of this study show that during intermittent high-intensity exercise, recovery intervals allow intramuscular homeostasis to be restored, with the degree of restoration being related to the duration of the recovery interval. Consequently, and consistent with the intermittent CP model, the ability to perform W>CP during intermittent high-intensity exercise and, therefore, exercise tolerance, increases when recovery-interval duration is extended.
Abstract.
Author URL.
Vanhatalo A, Bailey SJ, Dimenna FJ, Blackwell JR, Wallis GA, Jones AM (2013). No effect of acute L-arginine supplementation on O<inf>2</inf> cost or exercise tolerance.
European Journal of Applied Physiology,
113(7), 1805-1819.
Abstract:
No effect of acute L-arginine supplementation on O2 cost or exercise tolerance
The extent to which dietary supplementation with the nitric oxide synthase (NOS) substrate, l-arginine (ARG), impacts on NO production and NO-mediated physiological responses is controversial. This randomised, double blinded, cross-over study investigated the effects of acute ARG supplementation on NO biomarkers, O2 cost of exercise and exercise tolerance in humans. In one experiment, 15 subjects completed moderate- and severe-intensity running bouts after acute supplementation with 6 g ARG or placebo (PLA). In another experiment, eight subjects completed moderate- and severe-intensity cycling bouts after acute supplementation with 6 g ARG plus 25 g of carbohydrate (ARG + CHO) or an energy-matched dose of carbohydrate alone (CHO). The plasma nitrite concentration was not different after ARG (Pre: 204 ± 79; Post: 241 ± 114 nM; P > 0.05) or ARG + CHO consumption (Pre: 304 ± 57; Post: 335 ± 116 nM; P > 0.05). During moderate-intensity exercise, the steady-state pulmonary V̇O2 was not different, relative to the respective placebo conditions, after ARG (PLA: 2,407 ± 318, ARG: 2,422 ± 333 mL min-1) or ARG + CHO (CHO: 1,695 ± 304, ARG + CHO: 1,712 ± 312 mL min-1) ingestion (P > 0.05). The tolerable duration of severe exercise was also not significantly different (P > 0.05) after ingesting ARG (PLA: 551 ± 140, ARG: 552 ± 150 s) or ARG + CHO (CHO: 457 ± 182, ARG + CHO: 441 ± 221 s). In conclusion, acute dietary supplementation with ARG or ARG + CHO did not alter biomarkers of NO synthesis, O2 cost of exercise or exercise tolerance in healthy subjects. © 2013 Springer-Verlag Berlin Heidelberg.
Abstract.
Vanhatalo A, Bailey SJ, DiMenna FJ, Blackwell JR, Wallis GA, Jones AM (2013). No effect of acute L-arginine supplementation on O₂ cost or exercise tolerance.
Eur J Appl Physiol,
113(7), 1805-1819.
Abstract:
No effect of acute L-arginine supplementation on O₂ cost or exercise tolerance.
The extent to which dietary supplementation with the nitric oxide synthase (NOS) substrate, L-arginine (ARG), impacts on NO production and NO-mediated physiological responses is controversial. This randomised, double blinded, cross-over study investigated the effects of acute ARG supplementation on NO biomarkers, O₂ cost of exercise and exercise tolerance in humans. In one experiment, 15 subjects completed moderate- and severe-intensity running bouts after acute supplementation with 6 g ARG or placebo (PLA). In another experiment, eight subjects completed moderate- and severe-intensity cycling bouts after acute supplementation with 6 g ARG plus 25 g of carbohydrate (ARG + CHO) or an energy-matched dose of carbohydrate alone (CHO). The plasma nitrite concentration was not different after ARG (Pre: 204 ± 79; Post: 241 ± 114 nM; P > 0.05) or ARG + CHO consumption (Pre: 304 ± 57; Post: 335 ± 116 nM; P > 0.05). During moderate-intensity exercise, the steady-state pulmonary VO₂ was not different, relative to the respective placebo conditions, after ARG (PLA: 2,407 ± 318, ARG: 2,422 ± 333 mL min(-1)) or ARG + CHO (CHO: 1,695 ± 304, ARG + CHO: 1,712 ± 312 mL min(-1)) ingestion (P > 0.05). The tolerable duration of severe exercise was also not significantly different (P > 0.05) after ingesting ARG (PLA: 551 ± 140, ARG: 552 ± 150 s) or ARG + CHO (CHO: 457 ± 182, ARG + CHO: 441 ± 221 s). In conclusion, acute dietary supplementation with ARG or ARG + CHO did not alter biomarkers of NO synthesis, O₂ cost of exercise or exercise tolerance in healthy subjects.
Abstract.
Author URL.
Gibala MJ, Jones AM (2013). Physiological and performance adaptations to high-intensity interval training.
Nestle Nutr Inst Workshop Ser,
76, 51-60.
Abstract:
Physiological and performance adaptations to high-intensity interval training.
High-intensity interval training (HIIT) refers to exercise that is characterized by relatively short bursts of vigorous activity, interspersed by periods of rest or low-intensity exercise for recovery. In untrained and recreationally active individuals, short-term HIIT is a potent stimulus to induce physiological remodeling similar to traditional endurance training despite a markedly lower total exercise volume and training time commitment. As little as six sessions of 'all-out' HIIT over 14 days, totaling ∼15 min of intense cycle exercise within total training time commitment of ∼2.5 h, is sufficient to enhance exercise capacity and improve skeletal muscle oxidative capacity. From an athletic standpoint, HIIT is also an effective strategy to improve performance when supplemented into the already high training volumes of well-trained endurance athletes, although the underlying mechanisms are likely different compared to less trained subjects. Most studies in this regard have examined the effect of replacing a portion (typically ∼15-25%) of base/normal training with HIIT (usually 2-3 sessions per week for 4-8 weeks). It has been proposed that a polarized approach to training, in which ∼75% of total training volume be performed at low intensities, with 10-15% performed at very high intensities may be the optimal training intensity distribution for elite athletes who compete in intense endurance events.
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Author URL.
Mezzani A, Grassi B, Jones AM, Giordano A, Corrà U, Porcelli S, Della Bella S, Taddeo A, Giannuzzi P (2013). Speeding of pulmonary VO2 on-kinetics by light-to-moderate-intensity aerobic exercise training in chronic heart failure: clinical and pathophysiological correlates.
Int J Cardiol,
167(5), 2189-2195.
Abstract:
Speeding of pulmonary VO2 on-kinetics by light-to-moderate-intensity aerobic exercise training in chronic heart failure: clinical and pathophysiological correlates.
BACKGROUND: Pulmonary VO2 on-kinetics during light-to-moderate-intensity constant-work-rate exercise, an experimental model mirroring energetic transitions during daily activities, has been shown to speed up with aerobic exercise training (AET) in normal subjects, but scant data are available in chronic heart failure (CHF). METHODS AND RESULTS: Thirty CHF patients were randomized to 3 months of light-to-moderate-intensity AET (CHF-AET) or control (CHF-C). Baseline and end-protocol evaluations included i) one incremental cardiopulmonary exercise test with near infrared spectroscopy analysis of peak deoxygenated hemoglobin+myoglobin concentration changes (Δ[deoxy(Hb+Mb)]) in vastus lateralis muscle, ii) 8 light-to-moderate-intensity constant-work-rate exercise tests for VO2 on-kinetics phase I duration, phase II τ, and mean response time (MRT) assessment, and iii) circulating endothelial progenitor cell (EPC) measurement. Reference values were obtained in 7 age-matched normals (N). At end-protocol, phase I duration, phase II τ, and MRT were significantly reduced (-12%, -22%, and -19%, respectively) and peak VO2, peak Δ[deoxy(Hb+Mb)], and EPCs increased (9%, 20%, and 98%, respectively) in CHF-AET, but not in CHF-C. Peak Δ[deoxy(Hb+Mb)] and EPCs relative increase correlated significantly to that of peak VO2 (r=0.61 and 0.64, respectively, p
Abstract.
Author URL.
Mezzani A, Grassi B, Jones AM, Giordano A, Corrà U, Porcelli S, Della Bella S, Taddeo A, Giannuzzi P (2013). Speeding of pulmonary VO<inf>2</inf> on-kinetics by light-to-moderate- intensity aerobic exercise training in chronic heart failure: Clinical and pathophysiological correlates.
International Journal of Cardiology,
167(5), 2189-2195.
Abstract:
Speeding of pulmonary VO2 on-kinetics by light-to-moderate- intensity aerobic exercise training in chronic heart failure: Clinical and pathophysiological correlates
Background: Pulmonary VO2 on-kinetics during light-to-moderate-intensity constant-work-rate exercise, an experimental model mirroring energetic transitions during daily activities, has been shown to speed up with aerobic exercise training (AET) in normal subjects, but scant data are available in chronic heart failure (CHF). Methods and results: Thirty CHF patients were randomized to 3 months of light-to-moderate-intensity AET (CHF-AET) or control (CHF-C). Baseline and end-protocol evaluations included i) one incremental cardiopulmonary exercise test with near infrared spectroscopy analysis of peak deoxygenated hemoglobin + myoglobin concentration changes (Δ[deoxy(Hb + Mb)]) in vastus lateralis muscle, ii) 8 light-to-moderate- intensity constant-work-rate exercise tests for VO2 on-kinetics phase I duration, phase II τ, and mean response time (MRT) assessment, and iii) circulating endothelial progenitor cell (EPC) measurement. Reference values were obtained in 7 age-matched normals (N). At end-protocol, phase I duration, phase II τ, and MRT were significantly reduced (- 12%, - 22%, and - 19%, respectively) and peak VO2, peak Δ[deoxy(Hb + Mb)], and EPCs increased (9%, 20%, and 98%, respectively) in CHF-AET, but not in CHF-C. Peak Δ[deoxy(Hb + Mb)] and EPCs relative increase correlated significantly to that of peak VO2 (r = 0.61 and 0.64, respectively, p < 0.05). Conclusions: Light-to-moderate-intensity AET determined a near-normalization of pulmonary VO2 on-kinetics in CHF patients. Such a marked plasticity has important implications for AET intensity prescription, especially in patients more functionally limited and with high exercise-related risk. The AET-induced simultaneous improvement of phase I and phase II, associated with an increase of peak peripheral oxygen extraction and EPCs, supports microcirculatory O2 delivery impairment as a key factor determining exercise intolerance in CHF. © 2012 Elsevier Ireland Ltd.
Abstract.
Moore IS, Jones A, Dixon S (2013). The pursuit of improved running performance: can changes in cushioning and proprioception influence running economy and injury risk?. Footwear Science, 5(SUPPL. 1).
Chidnok W, Dimenna FJ, Bailey SJ, Burnley M, Wilkerson DP, Vanhatalo A, Jones AM (2013). V̇O<inf>2max</inf> is not altered by self-pacing during incremental exercise.
European Journal of Applied Physiology,
113(2), 529-539.
Abstract:
V̇O2max is not altered by self-pacing during incremental exercise
We tested the hypothesis that incremental cycling to exhaustion that is paced using clamps of the rating of perceived exertion (RPE) elicits higher V̇O2max values compared to a conventional ramp incremental protocol when test duration is matched. Seven males completed three incremental tests to exhaustion to measure V̇O2max. The incremental protocols were of similar duration and included: a ramp test at 30 W min-1 with constant cadence (RAMP1); a ramp test at 30 W min-1 with cadence free to fluctuate according to subject preference (RAMP2); and a self-paced incremental test in which the power output was selected by the subject according to prescribed increments in RPE (SPT). The subjects also completed a V̇O2max 'verification' test at a fixed high-intensity power output and a 3-min all-out test. No difference was found for V̇O 2max between the incremental protocols (RAMP1 = 4.33 ± 0.60 L min-1; RAMP2 = 4.31 ± 0.62 L min-1; SPT = 4.36 ± 0.59 L min-1; P > 0.05) nor between the incremental protocols and the peak V̇O2max measured during the 3-min all-out test (4.33 ± 0.68 L min-1) or the V̇O2max measured in the verification test (4.32 ± 0.69 L min-1). The integrated electromyogram, blood lactate concentration, heart rate and minute ventilation at exhaustion were not different (P > 0.05) between the incremental protocols. In conclusion, when test duration is matched, SPT does not elicit a higher V̇O2max compared to conventional incremental protocols. The striking similarity of V̇O2max measured across an array of exercise protocols indicates that there are physiological limits to the attainment of V̇O2max that cannot be exceeded by self-pacing. © 2012 Springer-Verlag.
Abstract.
Chidnok W, Dimenna FJ, Bailey SJ, Burnley M, Wilkerson DP, Vanhatalo A, Jones AM (2013). V̇O<inf>2max</inf> is not altered by self-pacing during incremental exercise: Reply to the letter of Alexis R. Mauger. European Journal of Applied Physiology, 113(2), 543-544.
Ferguson SK, Hirai DM, Copp SW, Holdsworth CT, Hageman KS, Jones AM, Musch TI, Poole DC (2012). Acute Dietary Nitrate Supplementation on Resting and Exercising Muscle Hemodynamic Control in the Rat.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
44, 879-879.
Author URL.
Engan HK, Jones AM, Ehrenberg F, Schagatay E (2012). Acute dietary nitrate supplementation improves dry static apnea performance.
Respir Physiol Neurobiol,
182(2-3), 53-59.
Abstract:
Acute dietary nitrate supplementation improves dry static apnea performance.
Acute dietary nitrate (NO₃⁻) supplementation has been reported to lower resting blood pressure, reduce the oxygen (O₂) cost of sub-maximal exercise, and improve exercise tolerance. Given the proposed effects of NO₃⁻ on tissue oxygenation and metabolic rate, it is possible that NO₃⁻ supplementation might enhance the duration of resting apnea. If so, this might have important applications both in medicine and sport. We investigated the effects of acute NO₃⁻ supplementation on pre-apnea blood pressure, apneic duration, and the heart rate (HR) and arterial O₂ saturation (SaO₂) responses to sub-maximal and maximal apneas in twelve well-trained apnea divers. Subjects were assigned in a randomized, double blind, crossover design to receive 70 ml of beetroot juice (BR; containing ∼5.0 mmol of nitrate) and placebo juice (PL; ∼0.003 mmol of nitrate) treatments. At 2.5 h post-ingestion, the subjects completed a series of two 2-min (sub-maximal) static apneas separated by 3 min of rest, followed by a maximal effort apnea. Relative to PL, BR reduced resting mean arterial pressure by 2% (PL: 86±7 vs. BR: 84 ± 6 mmHg; P=0.04). The mean nadir for SaO₂ after the two sub-maximal apneas was 97.2±1.6% in PL and 98.5±0.9% in BR (P=0.03) while the reduction in HR from baseline was not significantly different between PL and BR. Importantly, BR increased maximal apneic duration by 11% (PL: 250 ± 58 vs. BR: 278±64s; P=0.04). In the longer maximal apneas in BR, the magnitude of the reductions in HR and SaO₂ were greater than in PL (P ≤ 0.05). The results suggest that acute dietary NO₃⁻ supplementation may increase apneic duration by reducing metabolic costs.
Abstract.
Author URL.
Mezzani A, Hamm LF, Jones AM, McBride PE, Moholdt T, Stone JA, Urhausen A, Williams MA, European Association for Cardiovascular Prevention and Rehabilitation, American Association of Cardiovascular and Pulmonary Rehabilitation, et al (2012). Aerobic exercise intensity assessment and prescription in cardiac rehabilitation: a joint position statement of the European Association for Cardiovascular Prevention and Rehabilitation, the American Association of Cardiovascular and Pulmonary Rehabilitation, and the Canadian Association of Cardiac Rehabilitation.
J Cardiopulm Rehabil Prev,
32(6), 327-350.
Abstract:
Aerobic exercise intensity assessment and prescription in cardiac rehabilitation: a joint position statement of the European Association for Cardiovascular Prevention and Rehabilitation, the American Association of Cardiovascular and Pulmonary Rehabilitation, and the Canadian Association of Cardiac Rehabilitation.
Aerobic exercise intensity prescription is a key issue in cardiac rehabilitation, being directly linked to both the amount of improvement in exercise capacity and the risk of adverse events during exercise. This joint position statement aims to provide professionals with up-to-date information regarding the identification of different exercise intensity domains, the methods of direct and indirect determination of exercise intensity for both continuous and interval aerobic training, the effects of the use of different exercise protocols on exercise intensity prescription and the indications for recommended exercise training prescription in specific cardiac patients' groups. The importance of functional evaluation through exercise testing prior to starting an aerobic training program is strongly emphasized, and ramp incremental cardiopulmonary exercise test, when available, is proposed as the gold standard for a physiologically comprehensive exercise intensity assessment and prescription. This may allow a shift from a 'range-based' to a 'threshold-based' aerobic exercise intensity prescription, which, combined with thorough clinical evaluation and exercise-related risk assessment, could maximize the benefits obtainable by the use of aerobic exercise training in cardiac rehabilitation.
Abstract.
Author URL.
Chidnok W, DiMenna FJ, Bailey SJ, Wilkerson DP, Vanhatalo A, Jones AM (2012). All-out Critical Power Test Predicts Time-to-exhaustion During Ramp Incremental and Constant-work-rate Exercise.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
44, 613-613.
Author URL.
Fudge BW, Pringle JSM, Maxwell NS, Turner G, Ingham SA, Jones AM (2012). Altitude training for elite endurance performance: a 2012 update.
Curr Sports Med Rep,
11(3), 148-154.
Abstract:
Altitude training for elite endurance performance: a 2012 update.
Altitude training is commonly used by endurance athletes and coaches in pursuit of enhancement of performance on return to sea level. The purpose of the current review article was to update and evaluate recent literature relevant to the practical application of altitude training for endurance athletes. Consequently, the literature can be considered in either of two categories: performance-led investigations or mechanistic advancements/insights. Each section discusses the relevant literature and proposes future directions where appropriate.
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Author URL.
Kelly J, Vanhatalo A, Fulford J, French O, Blackwell JR, Jones AM (2012). Dietary Nitrate Supplementation Reduces the Oxygen Cost of Exercise in Healthy Older Adults.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
44, 443-443.
Author URL.
Jones AM, Bailey SJ, Vanhatalo A (2012). Dietary nitrate and O₂ consumption during exercise.
Med Sport Sci,
59, 29-35.
Abstract:
Dietary nitrate and O₂ consumption during exercise.
Recent studies have investigated the influence of dietary nitrate supplementation on the physiological responses to exercise. Specifically, it has been reported that enhancing nitric oxide (NO) bioavailability through supplementation of the diet with nitrate salts or nitrate-rich beetroot juice reduces the O(2) cost of exercise and improves exercise performance. The lower O(2) cost for a given sub-maximal work rate following nitrate ingestion indicates that muscle efficiency is enhanced either as a consequence of a reduced energy cost of contraction or enhanced mitochondrial efficiency. The positive effects of nitrate supplementation on the O(2) cost of sub-maximal exercise can be manifested acutely (i.e. 2.5 h following ingestion) and maintained for at least 15 days if supplementation is continued. Most recently, the influence of dietary nitrate supplementation on time trial performance in competitive cyclists has been investigated. Studies have shown a 1-2% reduction in the time to complete time trial distances between 4 and 16 km. The dose of nitrate that has been shown to improve exercise efficiency can readily be achieved through the consumption of 0.5 litre of beetroot juice or an equivalent high-nitrate foodstuff. Following a 5- to 6-mmol bolus of nitrate, plasma [nitrite] typically peaks within 2-3 h and remains elevated for a further 6-9 h before declining towards baseline. Therefore, consuming nitrate approximately 3 h prior to competition or training is recommended if athletes wish to explore the ergogenic potential of nitrate supplementation.
Abstract.
Author URL.
Burnley M, Vanhatalo A, Jones AM (2012). Distinct profiles of neuromuscular fatigue during muscle contractions below and above the critical torque in humans.
J Appl Physiol (1985),
113(2), 215-223.
Abstract:
Distinct profiles of neuromuscular fatigue during muscle contractions below and above the critical torque in humans.
Whether the transition in fatigue processes between "low-intensity" and "high-intensity" contractions occurs gradually, as the torque requirements are increased, or whether this transition occurs more suddenly at some identifiable "threshold", is not known. We hypothesized that the critical torque (CT; the asymptote of the torque-duration relationship) would demarcate distinct profiles of central and peripheral fatigue during intermittent isometric quadriceps contractions (3-s contraction, 2-s rest). Nine healthy men performed seven experimental trials to task failure or for up to 60 min, with maximal voluntary contractions (MVCs) performed at the end of each minute. The first five trials were performed to determine CT [~35-55% MVC, denoted severe 1 (S1) to severe 5 (S5) in ascending order], while the remaining two trials were performed 10 and 20% below the CT (denoted CT-10% and CT-20%). Dynamometer torque and the electromyogram of the right vastus lateralis were sampled continuously. Peripheral and central fatigue was determined from the fall in potentiated doublet torque and voluntary activation, respectively. Above CT, contractions progressed to task failure in ~3-18 min, at which point the MVC did not differ from the target torque (S1 target, 88.7 ± 4.3 N·m vs. MVC, 89.3 ± 8.8 N·m, P = 0.94). The potentiated doublet fell significantly in all trials, and voluntary activation was reduced in trials S1-S3, but not trials S4 and S5. Below CT, contractions could be sustained for 60 min on 17 of 18 occasions. Both central and peripheral fatigue developed, but there was a substantial reserve in MVC torque at the end of the task. The rate of global and peripheral fatigue development was four to five times greater during S1 than during CT-10% (change in MVC/change in time S1 vs. CT-10%: -7.2 ± 1.4 vs. -1.5 ± 0.4 N·m·min(-1)). These results demonstrate that CT represents a critical threshold for neuromuscular fatigue development.
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Author URL.
Stone MR, Thomas K, Wilkinson M, Jones AM, St Clair Gibson A, Thompson KG (2012). Effects of deception on exercise performance: implications for determinants of fatigue in humans.
Med Sci Sports Exerc,
44(3), 534-541.
Abstract:
Effects of deception on exercise performance: implications for determinants of fatigue in humans.
PURPOSE: the aim of this study was to investigate whether it was possible to reduce the time taken to complete a 4000-m cycling time trial by misleading participants into believing they were racing against a previous trial, when, in fact, the power output was 2% greater. METHODS: Nine trained male cyclists each completed four 4000-m time trials. The first trial was a habituation and the data from the second trial was used to form a baseline (BL). During trials 3 and 4, participants raced against an avatar, which they were informed represented their BL performance. However, whereas one of these trials was an accurate (ACC) representation of BL, the power output in the other trial was set at 102% of BL and formed the deception condition (DEC). Oxygen uptake and RER were measured continuously and used to determine aerobic and anaerobic contributions to power output. RESULTS: There was a significant difference between trials for time to completion (F = 15.3, P = 0.00). Participants completed DEC more quickly than BL (90% CI = 2.1-10.1 s) and ACC (90% CI = 1.5-5.4 s) and completed ACC more quickly than BL (90% CI = 0.5-4.8 s). The difference in performance between DEC and ACC was attributable to a greater anaerobic contribution to power output at 90% of the total distance (F = 5.3, P = 0.02, 90% CI = 4-37 W). CONCLUSIONS: the provision of surreptitiously augmented feedback derived from a previous performance reduces time taken for cyclists to accomplish a time trial of known duration. This suggests that cyclists operate with a metabolic reserve even during maximal time trials and that this reserve can be accessed after deception.
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Author URL.
Chidnok W, Dimenna FJ, Bailey SJ, Vanhatalo A, Morton RH, Wilkerson DP, Jones AM (2012). Exercise tolerance in intermittent cycling: Application of the critical power concept.
Medicine and Science in Sports and Exercise,
44(5), 966-976.
Abstract:
Exercise tolerance in intermittent cycling: Application of the critical power concept
Purpose: This study tested the relevance of the critical power (CP) model for explaining exercise tolerance during intermittent high-intensity exercise with different recovery intensities. Methods: After estimation of CP and W′ from a 3-min all-out test, seven male subjects completed, in randomized order, a cycle test to exhaustion at a severe-intensity constant-work-rate (S-CWR) and four cycle tests to exhaustion using different intermittent ("work-recovery") protocols (i.e. severe-severe (S-S), severe-heavy (S-H), severe-moderate (S-M), and severe-light (S-L)). Results: the tolerable duration of exercise in S-CWR was 384 ± 48 s, and this was increased by 47%, 100%, and 219% for S-H, S-M, and S-L, respectively (all P < 0.05). Consistent with this, compared with S-CWR (22.9 ± 7.4 kJ), the work done above the CP was significantly greater by 46%, 98%, and 220% for S-H, S-M, and S-L, respectively (all P < 0.05). The slope of the relationship between V̇O 2 and time was significantly reduced for S-H, S-M, and S-L (0.09 ± 0.02, 0.09 ± 0.01, and 0.07 ± 0.02 L•min -2, respectively) compared with S-CWR (0.16 ± 0.03 L•min -2, P < 0.05). In addition, the slope of the relationship between integrated EMG and time showed a systematic decline for S-H, S-M, and S-L compared with S-CWR (P < 0.05). Conclusions: These results indicate that, when recovery intervals during intermittent exercise are performed below the CP, exercise tolerance is improved in proportion to the reconstitution of the finite W′. The enhanced exercise tolerance with the lower-intensity recovery intervals was associated with a blunted increase in both V̇O 2 and integrated EMG with time. © 2012 by the American College of Sports Medicine.
Abstract.
Chidnok W, Dimenna FJ, Bailey SJ, Vanhatalo A, Morton RH, Wilkerson DP, Jones AM (2012). Exercise tolerance in intermittent cycling: application of the critical power concept.
Med Sci Sports Exerc,
44(5), 966-976.
Abstract:
Exercise tolerance in intermittent cycling: application of the critical power concept.
PURPOSE: This study tested the relevance of the critical power (CP) model for explaining exercise tolerance during intermittent high-intensity exercise with different recovery intensities. METHODS: After estimation of CP and W' from a 3-min all-out test, seven male subjects completed, in randomized order, a cycle test to exhaustion at a severe-intensity constant-work-rate (S-CWR) and four cycle tests to exhaustion using different intermittent ("work-recovery") protocols (i.e. severe-severe (S-S), severe-heavy (S-H), severe-moderate (S-M), and severe-light (S-L)). RESULTS: the tolerable duration of exercise in S-CWR was 384 ± 48 s, and this was increased by 47%, 100%, and 219% for S-H, S-M, and S-L, respectively (all P < 0.05). Consistent with this, compared with S-CWR (22.9 ± 7.4 kJ), the work done above the CP was significantly greater by 46%, 98%, and 220% for S-H, S-M, and S-L, respectively (all P < 0.05). The slope of the relationship between V˙O₂ and time was significantly reduced for S-H, S-M, and S-L (0.09 ± 0.02, 0.09 ± 0.01, and 0.07 ± 0.02 L·min⁻², respectively) compared with S-CWR (0.16 ± 0.03 L·min⁻², P < 0.05). In addition, the slope of the relationship between integrated EMG and time showed a systematic decline for S-H, S-M, and S-L compared with S-CWR (P < 0.05). CONCLUSIONS: These results indicate that, when recovery intervals during intermittent exercise are performed below the CP, exercise tolerance is improved in proportion to the reconstitution of the finite W'. The enhanced exercise tolerance with the lower-intensity recovery intervals was associated with a blunted increase in both V˙O₂ and integrated EMG with time.
Abstract.
Author URL.
Wilkerson DP, Hayward GM, Bailey SJ, Vanhatalo A, Blackwell JR, Jones AM (2012). Influence of acute dietary nitrate supplementation on 50 mile time trial performance in well-trained cyclists.
European Journal of Applied Physiology,
112(12), 4127-4134.
Abstract:
Influence of acute dietary nitrate supplementation on 50 mile time trial performance in well-trained cyclists
Dietary nitrate supplementation has been reported to improve short distance time trial (TT) performance by 1-3 % in club-level cyclists. It is not known if these ergogenic effects persist in longer endurance events or if dietary nitrate supplementation can enhance performance to the same extent in better trained individuals. Eight well-trained male cyclists performed two laboratorybased 50 mile TTs: (1) 2.5 h after consuming 0.5 L of nitrate-rich beetroot juice (BR) and (2) 2.5 h after consuming 0.5 L of nitrate-depleted BR as a placebo (PL). BR significantly elevated plasma [NO2 -] (BR: 472 ± 96 vs. PL: 379 ± 94 nM; P0.05) but oxygen uptake ( VO2) tended to be lower in BR (P = 0.06), resulting in a significantly greater PO/ VO2 ratio (BR: 67.4 ± 5.5 vs. PL: 65.3 ± 4.8 W L min-1; P
Abstract.
Wilkerson DP, Hayward GM, Bailey SJ, Vanhatalo A, Blackwell JR, Jones AM (2012). Influence of acute dietary nitrate supplementation on 50 mile time trial performance in well-trained cyclists.
Eur J Appl Physiol,
112(12), 4127-4134.
Abstract:
Influence of acute dietary nitrate supplementation on 50 mile time trial performance in well-trained cyclists.
Dietary nitrate supplementation has been reported to improve short distance time trial (TT) performance by 1-3 % in club-level cyclists. It is not known if these ergogenic effects persist in longer endurance events or if dietary nitrate supplementation can enhance performance to the same extent in better trained individuals. Eight well-trained male cyclists performed two laboratory-based 50 mile TTs: (1) 2.5 h after consuming 0.5 L of nitrate-rich beetroot juice (BR) and (2) 2.5 h after consuming 0.5 L of nitrate-depleted BR as a placebo (PL). BR significantly elevated plasma [NO(2) (-)] (BR: 472 ± 96 vs. PL: 379 ± 94 nM; P 0.05). There was a significant correlation between the increased post-beverage plasma [NO(2) (-)] with BR and the reduction in TT completion time (r = -0.83, P = 0.01). Power output (PO) was not different between the conditions at any point (P > 0.05) but oxygen uptake ([Formula: see text]O(2)) tended to be lower in BR (P = 0.06), resulting in a significantly greater PO/[Formula: see text]O(2) ratio (BR: 67.4 ± 5.5 vs. PL: 65.3 ± 4.8 W L min(-1); P
Abstract.
Author URL.
Jones AM, Krustrup P, Wilkerson DP, Berger NJ, Calbet JA, Bangsbo J (2012). Influence of exercise intensity on skeletal muscle blood flow, O2 extraction and O2 uptake on-kinetics.
J Physiol,
590(17), 4363-4376.
Abstract:
Influence of exercise intensity on skeletal muscle blood flow, O2 extraction and O2 uptake on-kinetics.
Following the start of low-intensity exercise in healthy humans, it has been established that the kinetics of skeletal muscle O(2) delivery is faster than, and does not limit, the kinetics of muscle O(2) uptake (V(O(2)(m))). Direct data are lacking, however, on the question of whether O(2) delivery might limit (V(O(2)(m))) kinetics during high-intensity exercise. Using multiple exercise transitions to enhance confidence in parameter estimation, we therefore investigated the kinetics of, and inter-relationships between, muscle blood flow (Q(m)), a-(V(O(2))) difference and (V(O(2)(m))) following the onset of low-intensity (LI) and high-intensity (HI) exercise. Seven healthy males completed four 6 min bouts of LI and four 6 min bouts of HI single-legged knee-extension exercise. Blood was frequently drawn from the femoral artery and vein during exercise and Q(m), a-(V(O(2))) difference and (V(O(2)(m))) were calculated and subsequently modelled using non-linear regression techniques. For LI, the fundamental component mean response time (MRT(p)) for Q(m) kinetics was significantly shorter than (V(O(2)(m))) kinetics (mean ± SEM, 18 ± 4 vs. 30 ± 4 s; P < 0.05), whereas for HI, the MRT(p) for Q(m) and (V(O(2)(m))) was not significantly different (27 ± 5 vs. 29 ± 4 s, respectively). There was no difference in the MRT(p) for either Q(m) or (V(O(2)(m))) between the two exercise intensities; however, the MRT(p)for a-(V(O(2)) difference was significantly shorter for HI compared with LI (17 ± 3 vs. 28 ± 4 s; P < 0.05). Excess O(2), i.e. oxygen not taken up (Q(m) x (V(O(2))), was significantly elevated within the first 5 s of exercise and remained unaltered thereafter, with no differences between LI and HI. These results indicate that bulk O(2) delivery does not limit (V(O(2)(m))) kinetics following the onset of LI or HI knee-extension exercise.
Abstract.
Author URL.
Simpson LP, Jones AM, Vanhatalo A, Wilkerson DP (2012). Influence of initial metabolic rate on the power-duration relationship for all-out exercise.
European Journal of Applied Physiology,
112(7), 2467-2473.
Abstract:
Influence of initial metabolic rate on the power-duration relationship for all-out exercise
A single 3-min all-out cycling test can be used to estimate the power asymptote (critical power, CP) and the curvature constant (W′) of the power-duration relationship for severe-intensity exercise. It was hypothesized that when exercise immediately preceding the 3-min all-out test was performed CP would systematically reduce the W′ without affecting the CP. Seven physically active males completed 3-min all-out cycling tests in randomized order immediately preceded by: unloaded cycling (control); 6-min moderate; 6-min heavy; 2-min severe (S2); or 4-min severe (S4) intensity exercise. The CP was estimated from the mean power output over the final 30 s of the test and the W′ was estimated as the power-time integral above end-test power. There were no significant differences in the CP between control (279 ± 62), moderate (275 ± 52), heavy (286 ± 66 W), S2 (274 ± 55), or S4 (273 ± 65 W). The W′ was significantly lower (P < 0.05) in S2 (11.5 ± 2.5) and S4 (8.9 ± 2.2) than in control (16.3 ± 2.3), moderate (17.2 ± 2.4) and heavy (15.6 ± 2.3 kJ). These results support the notion that the W′ is predictably depleted only at a power output >CP whereas the CP is independent of the mechanisms which reduce W′. © Springer-Verlag 2011.
Abstract.
Parker Simpson L, Jones AM, Vanhatalo A, Wilkerson DP (2012). Influence of initial metabolic rate on the power-duration relationship for all-out exercise.
Eur J Appl Physiol,
112(7), 2467-2473.
Abstract:
Influence of initial metabolic rate on the power-duration relationship for all-out exercise.
A single 3-min all-out cycling test can be used to estimate the power asymptote (critical power, CP) and the curvature constant (W') of the power-duration relationship for severe-intensity exercise. It was hypothesized that when exercise immediately preceding the 3-min all-out test was performed
Abstract.
Author URL.
Bailey SJ, Wilkerson DP, Fulford J, Jones AM (2012). Influence of passive lower-body heating on muscle metabolic perturbation and high-intensity exercise tolerance in humans.
European Journal of Applied Physiology,
112(10), 3569-3576.
Abstract:
Influence of passive lower-body heating on muscle metabolic perturbation and high-intensity exercise tolerance in humans
The purpose of this investigation was to determine the influence of heat stress on the dynamics of muscle metabolic perturbation during high-intensity exercise. Seven healthy males completed single-legged knee-extensor exercise until the limit of tolerance on two separate occasions. In a randomized order the subjects underwent 40 min of lowerbody immersion in warm water at 42°C prior to exercise (HOT) or received no prior thermal manipulation (CON). Following the intervention, muscle metabolism was measured at rest and throughout exercise using 31P-MRS. The tolerable duration of high-intensity exercise was reduced by 36% after passive heating (CON:474 ± 146 vs. HOT:303 ± 76 s; P = 0.005). Intramuscular pH was lower over the first 60 s of exercise (CON:7.05 ± 0.02 vs. HOT:7.00 ± 0.03; P = 0.019) in HOT compared to CON. The rate of muscle [PCr] degradation during exercise was greater in the HOT condition (CON: -0.17 ± 0.08 vs. HOT: -0.25 ± 0.10% s-1; P = 0.006) and pH also tended to change more rapidly in HOT (P = 0.09). Muscle [PCr] (CON:26 ± 14 vs. HOT:29 ± 10%), [Pi] (CON:504 ± 236 vs. HOT:486 ± 186%) and pH (CON:6.84 ± 0.13 vs. HOT:6.80 ± 0.14; P>0.05) were not statistically different at the limit of tolerance (P>0.05 for all comparisons). These results suggest that the reduced time-to-exhaustion during high-intensity knee-extensor exercise following lower-body heating might be related, in part, to accelerated rates of change of intramuscular [PCr] and pH towards 'critical' values that limit muscle function. © Springer-Verlag 2012.
Abstract.
Bailey SJ, Wilkerson DP, Fulford J, Jones AM (2012). Influence of passive lower-body heating on muscle metabolic perturbation and high-intensity exercise tolerance in humans.
Eur J Appl Physiol,
112(10), 3569-3576.
Abstract:
Influence of passive lower-body heating on muscle metabolic perturbation and high-intensity exercise tolerance in humans.
The purpose of this investigation was to determine the influence of heat stress on the dynamics of muscle metabolic perturbation during high-intensity exercise. Seven healthy males completed single-legged knee-extensor exercise until the limit of tolerance on two separate occasions. In a randomized order the subjects underwent 40 min of lower-body immersion in warm water at 42°C prior to exercise (HOT) or received no prior thermal manipulation (CON). Following the intervention, muscle metabolism was measured at rest and throughout exercise using (31)P-MRS. The tolerable duration of high-intensity exercise was reduced by 36% after passive heating (CON: 474 ± 146 vs. HOT: 303 ± 76 s; P = 0.005). Intramuscular pH was lower over the first 60 s of exercise (CON: 7.05 ± 0.02 vs. HOT: 7.00 ± 0.03; P = 0.019) in HOT compared to CON. The rate of muscle [PCr] degradation during exercise was greater in the HOT condition (CON: -0.17 ± 0.08 vs. HOT: -0.25 ± 0.10% s(-1); P = 0.006) and pH also tended to change more rapidly in HOT (P = 0.09). Muscle [PCr] (CON: 26 ± 14 vs. HOT: 29 ± 10%), [Pi] (CON: 504 ± 236 vs. HOT: 486 ± 186%) and pH (CON: 6.84 ± 0.13 vs. HOT: 6.80 ± 0.14; P > 0.05) were not statistically different at the limit of tolerance (P > 0.05 for all comparisons). These results suggest that the reduced time-to-exhaustion during high-intensity knee-extensor exercise following lower-body heating might be related, in part, to accelerated rates of change of intramuscular [PCr] and pH towards 'critical' values that limit muscle function.
Abstract.
Author URL.
McNarry MA, Welsman JR, Jones AM (2012). Influence of training status and maturity on pulmonary O2 uptake recovery kinetics following cycle and upper body exercise in girls.
Pediatr Exerc Sci,
24(2), 246-261.
Abstract:
Influence of training status and maturity on pulmonary O2 uptake recovery kinetics following cycle and upper body exercise in girls.
The influence of training status on pulmonary VO(2) recovery kinetics, and its interaction with maturity, has not been investigated in young girls. Sixteen prepubertal (Pre: trained (T, 11.4 ± 0.7 years), 8 untrained (UT, 11.5 ± 0.6 years)) and 8 pubertal (Pub: 8T, 14.2 ± 0.7 years; 8 UT, 14.5 ± 1.3 years) girls completed repeat transitions from heavy intensity exercise to a baseline of unloaded exercise, on both an upper and lower body ergometer. The VO2 recovery time constant was significantly shorter in the trained prepubertal and pubertal girls during both cycle (Pre: T, 26 ± 4 vs. UT, 32 ± 6; Pub: T, 28 ± 2 vs. UT, 35 ± 7 s; both p <. 05) and upper body exercise (Pre: T, 26 ± 4 vs. UT, 35 ± 6; Pub: T, 30 ± 4 vs. UT, 42 ± 3 s; both p <. 05). No interaction was evident between training status and maturity. These results demonstrate the sensitivity of VO(2) recovery kinetics to training in young girls and challenge the notion of a "maturational threshold" in the influence of training status on the physiological responses to exercise and recovery.
Abstract.
Author URL.
Nyberg M, Blackwell JR, Damsgaard R, Jones AM, Hellsten Y, Mortensen SP (2012). Lifelong physical activity prevents an age-related reduction in arterial and skeletal muscle nitric oxide bioavailability in humans.
J Physiol,
590(21), 5361-5370.
Abstract:
Lifelong physical activity prevents an age-related reduction in arterial and skeletal muscle nitric oxide bioavailability in humans.
Ageing has been proposed to be associated with increased levels of reactive oxygen species (ROS) that scavenge nitric oxide (NO). In eight young sedentary (23 ± 1 years; Y), eight older lifelong sedentary (66 ± 2 years; OS) and eight older lifelong physically active subjects (62 ± 2 years; OA), we studied the effect of ROS on systemic and skeletal muscle NO bioavailability and leg blood flow by infusion of the antioxidant N-acetylcysteine (NAC). Infusion of NAC increased the bioavailability of NO in OS, as evidenced by an increased concentration of stable metabolites of NO (NOx) in the arterial and venous circulation and in the muscle interstitium. In OA, infusion of NAC only increased NOx concentrations in venous plasma whereas in Y, infusion of NAC did not affect NOx concentrations. Skeletal muscle protein levels of endothelial and neuronal NO synthase were 32% and 24% higher, respectively, in OA than in OS. Exercise at 12 W elicited a lower leg blood flow response that was associated with a lower leg oxygen uptake in OS than in Y. The improved bioavailability of NO in OS did not increase blood flow during exercise. These data demonstrate that NO bioavailability is compromised in the systemic circulation and in the musculature of sedentary ageing humans due to increased oxidative stress. Lifelong physical activity opposes this effect within the trained musculature and in the arterial circulation. The lower blood flow response to leg exercise in ageing humans is not associated with a reduced NO bioavailability.
Abstract.
Author URL.
Moore IS, Jones AM, Dixon SJ (2012). Mechanisms for improved running economy in beginner runners.
Medicine and Science in Sports and Exercise,
44(9), 1756-1763.
Abstract:
Mechanisms for improved running economy in beginner runners
Controversy surrounds whether running mechanics make good predictors of running economy (RE) with little known about the development of an economical running gait. Purpose: the aim of this study was to identify if mechanical or physiological variables changed during 10 wk of running in beginners and whether these changes could account for any change in RE. Methods: a 10-wk running program (10wkRP) was completed by 10 female beginner runners. A bilateral three-dimensional kinematic and kinetic analysis, in addition to RE and lower body flexibility measurements, was performed before and after the 10wkRP. The Balke-Ware graded walking exercise test was performed before and after the 10wkRP to determine V̇O2max. Results: Seven kinematic and kinetic variables significantly changed from before to after training, in addition to a significant decrease in calf flexibility (27.3° ± 6.3° vs 23.9° ± 5.6°, P < 0.05). A significant improvement was seen in RE (224 ± 24 vs 205 ± 27 mL•kg-1•km -1, P < 0.05) and treadmill time to exhaustion (16.4 ± 3.2 vs 17.3 ± 2.8 min, P < 0.05); however, V̇O2max remained unchanged from before to after training (34.7 ± 5.1 vs 34.3 ± 5.6 mL•kg•min). Stepwise regression analysis showed three kinematic variables to explain 94.3% of the variance in change in RE. They were a less extended knee at toe off (P = 0.004), peak dorsiflexion occurring later in stance (P = 0.001), and a slower eversion velocity at touchdown (P = 0.042). The magnitude of change for each variable was 1.5%, 4.7%, and 34.1%, respectively. Conclusions: These results show that beginner runners naturally developed their running gait as they became more economical runners. © 2012 by the American College of Sports Medicine.
Abstract.
Moore IS, Jones AM, Dixon SJ (2012). Mechanisms for improved running economy in beginner runners.
Med Sci Sports Exerc,
44(9), 1756-1763.
Abstract:
Mechanisms for improved running economy in beginner runners.
UNLABELLED: Controversy surrounds whether running mechanics make good predictors of running economy (RE) with little known about the development of an economical running gait. PURPOSE: the aim of this study was to identify if mechanical or physiological variables changed during 10 wk of running in beginners and whether these changes could account for any change in RE. METHODS: a 10-wk running program (10 wkRP) was completed by 10 female beginner runners. A bilateral three-dimensional kinematic and kinetic analysis, in addition to RE and lower body flexibility measurements, was performed before and after the 10 wkRP. The Balke-Ware graded walking exercise test was performed before and after the 10 wkRP to determine VO2max. RESULTS: Seven kinematic and kinetic variables significantly changed from before to after training, in addition to a significant decrease in calf flexibility (27.3° ± 6.3° vs 23.9° ± 5.6°, P < 0.05). A significant improvement was seen in RE (224 ± 24 vs 205 ± 27 mL · kg(-1) · km(-1), P < 0.05) and treadmill time to exhaustion (16.4 ± 3.2 vs 17.3 ± 2.8 min, P < 0.05); however, VO2max remained unchanged from before to after training (34.7 ± 5.1 vs 34.3 ± 5.6 mL · kg(-1) · min(-1)). Stepwise regression analysis showed three kinematic variables to explain 94.3% of the variance in change in RE. They were a less extended knee at toe off (P = 0.004), peak dorsiflexion occurring later in stance (P = 0.001), and a slower eversion velocity at touchdown (P = 0.042). The magnitude of change for each variable was 1.5%, 4.7%, and 34.1%, respectively. CONCLUSIONS: These results show that beginner runners naturally developed their running gait as they became more economical runners.
Abstract.
Author URL.
Skiba PF, Chidnok W, Vanhatalo A, Jones AM (2012). Modeling the expenditure and reconstitution of work capacity above critical power.
Medicine and Science in Sports and Exercise,
44(8), 1526-1532.
Abstract:
Modeling the expenditure and reconstitution of work capacity above critical power
Purpose: the critical power (CP) model includes two constants: the CP and the W′ [P = (W′/t) + CP]. The W′ is the finite work capacity available above CP. Power output above CP results in depletion of the W′ complete depletion of the W′ results in exhaustion. Monitoring the W′ may be valuable to athletes during training and competition. Our purpose was to develop a function describing the dynamic state of the W′ during intermittent exercise. Methods: After determination of V̇O2max, CP, and W′, seven subjects completed four separate exercise tests on a cycle ergometer on different days. Each protocol comprised a set of intervals: 60 s at a severe power output, followed by 30-s recovery at a lower prescribed power output. The intervals were repeated until exhaustion. These data were entered into a continuous equation predicting balance of W′ remaining, assuming exponential reconstitution of the W′. The time constant was varied by an iterative process until the remaining modeled W′ = 0 at the point of exhaustion. Results: the time constants of W′ recharge were negatively correlated with the difference between sub-CP recovery power and CP. The relationship was best fit by an exponential (r = 0.77). The model-predicted W′ balance correlated with the temporal course of the rise in V̇O2 (r = 0.82-0.96). The model accurately predicted exhaustion of the W′ in a competitive cyclist during a road race. Conclusions: We have developed a function to track the dynamic state of the W′ during intermittent exercise. This may have important implications for the planning and real-time monitoring of athletic performance. © 2012 by the American College of Sports Medicine.
Abstract.
Skiba PF, Chidnok W, Vanhatalo A, Jones AM (2012). Modeling the expenditure and reconstitution of work capacity above critical power.
Med Sci Sports Exerc,
44(8), 1526-1532.
Abstract:
Modeling the expenditure and reconstitution of work capacity above critical power.
PURPOSE: the critical power (CP) model includes two constants: the CP and the W' [P = (W' / t) + CP]. The W' is the finite work capacity available above CP. Power output above CP results in depletion of the W' complete depletion of the W' results in exhaustion. Monitoring the W' may be valuable to athletes during training and competition. Our purpose was to develop a function describing the dynamic state of the W' during intermittent exercise. METHODS: After determination of V˙O(2max), CP, and W', seven subjects completed four separate exercise tests on a cycle ergometer on different days. Each protocol comprised a set of intervals: 60 s at a severe power output, followed by 30-s recovery at a lower prescribed power output. The intervals were repeated until exhaustion. These data were entered into a continuous equation predicting balance of W' remaining, assuming exponential reconstitution of the W'. The time constant was varied by an iterative process until the remaining modeled W' = 0 at the point of exhaustion. RESULTS: the time constants of W' recharge were negatively correlated with the difference between sub-CP recovery power and CP. The relationship was best fit by an exponential (r = 0.77). The model-predicted W' balance correlated with the temporal course of the rise in V˙O(2) (r = 0.82-0.96). The model accurately predicted exhaustion of the W' in a competitive cyclist during a road race. CONCLUSIONS: We have developed a function to track the dynamic state of the W' during intermittent exercise. This may have important implications for the planning and real-time monitoring of athletic performance.
Abstract.
Author URL.
HASKELL CF, KENNEDY DO, DODD F, TURNER L, JONES AM, PRICHARD J, BELL P, THOMPSON KG (2012). Modulation of cerebral blood flow parameters in humans following consumption of nitrate-rich beetroot juice. Appetite, 59(2).
Poole DC, Jones AM (2012). Oxygen uptake kinetics.
Comprehensive Physiology,
2(2), 933-996.
Abstract:
Oxygen uptake kinetics
Muscular exercise requires transitions to and from metabolic rates often exceeding an order of magnitude above resting and places prodigious demands on the oxidative machinery and O2-transport pathway. The science of kinetics seeks to characterize the dynamic profiles of the respiratory, cardiovascular, and muscular systems and their integration to resolve the essential control mechanisms of muscle energetics and oxidative function: a goal not feasible using the steady-state response. Essential features of the O2 uptake (V̇O2) kinetics response are highly conserved across the animal kingdom. For a given metabolic demand, fast V̇O2 kinetics mandates a smaller O2 deficit, less substrate-level phosphorylation and high exercise tolerance. By the same token, slow V̇ O2 kinetics incurs a high O2 deficit, presents a greater challenge to homeostasis and presages poor exercise tolerance. Compelling evidence supports that, in healthy individuals walking, running, or cycling upright, VO2 kinetics control resides within the exercising muscle(s) and is therefore not dependent upon, or limited by, upstream O2-transport systems. However, disease, aging, and other imposed constraints may redistribute V̇ O2 kinetics control more proximally within the O2-transport system. Greater understanding of V̇ O2 kinetics control and, in particular, its relation to the plasticity of the O2-transport/utilization system is considered important for improving the human condition, not just in athletic populations, but crucially for patients suffering from pathologically slowed V̇ O2 kinetics as well as the burgeoning elderly population. © 2012 American Physiological Society.
Abstract.
Breese BC, Barker AR, Armstrong N, Jones AM, Williams CA (2012). The effect of baseline metabolic rate on pulmonary O₂ uptake kinetics during very heavy intensity exercise in boys and men.
Respir Physiol Neurobiol,
180(2-3), 223-229.
Abstract:
The effect of baseline metabolic rate on pulmonary O₂ uptake kinetics during very heavy intensity exercise in boys and men.
This study tested the hypothesis that pulmonary VO₂ kinetics would be slowed during 'work-to-work' exercise in adults but not in children. Eight boys (mean age=12.5 ± 0.5 years) and nine men completed very heavy step transitions initiated from either 'unloaded' pedalling (U→VH) or unloaded-to-moderate cycling (i.e. U→M to M→VH). The phase II τ was significantly (p
Abstract.
Author URL.
Bailey SJ, Vanhatalo A, Winyard PG, Jones AM (2012). The nitrate-nitrite-nitric oxide pathway: its role in human exercise physiology.
European Journal of Sport Science,
12(4), 309-320.
Abstract:
The nitrate-nitrite-nitric oxide pathway: its role in human exercise physiology
Nitric oxide (NO) is a potent signalling molecule that influences an array of physiological responses. It was traditionally assumed that NO was derived exclusively via the nitric oxide synthase (NOS) family of enzymes. This complex reaction requires a five electron oxidation of L-arginine and is contingent on the presence of numerous essential substrates (including O 2) and co-factors. Recently an additional, O 2-independent, NO generating pathway has been identified, where nitrite (NO 2-) can undergo a simple one electron reduction to yield NO. NO 2- is produced endogenously from the oxidation of NO and also from the reduction of dietary nitrate (NO 3-) by facultative bacteria residing on the tongue. Recent data show that dietary NO 3- supplementation, which increases the circulating plasma [NO 2-], reduces the O 2 cost of submaximal exercise in healthy humans. This finding is striking given that efficiency during moderate-intensity exercise has been considered to be immutable. There is evidence that the muscle ATP turnover at a fixed work rate is reduced and the mitochondrial P/O ratio is increased following NO 3- supplementation, which offers important insights into the physiological bases for the reduced V̇O 2 during exercise. NO 3- supplementation has also been shown to improve exercise performance in both healthy and patient populations. Therefore, dietary NO 3- supplementation may represent a practical and cost-effective method to improve exercise efficiency and exercise tolerance in humans. Given that a NO 3--rich diet may have numerous cardiovascular and other health benefits, dietary NO 3- intake may have important implications for human lifelong health and performance. © 2012 Copyright European College of Sport Science.
Abstract.
Chidnok W, DiMenna FJ, Bailey SJ, Burnley M, Wilkerson DP, Vanhatalo A, Jones AM (2012). {Mathematical expression} is not altered by self-pacing during incremental exercise. European Journal of Applied Physiology, 1-11.
Chidnok W, DiMenna FJ, Bailey SJ, Burnley M, Wilkerson DP, Vanhatalo A, Jones AM (2012). {Mathematical expression} is not altered by self-pacing during incremental exercise: reply to the letter of Alexis R. Mauger. European Journal of Applied Physiology, 1-2.
Lansley KE, Dimenna FJ, Bailey SJ, Jones AM (2011). A 'new' method to normalise exercise intensity.
Int J Sports Med,
32(7), 535-541.
Abstract:
A 'new' method to normalise exercise intensity.
Exercise intensity has traditionally been described, prescribed and normalised as a fraction (%) of the maximal oxygen uptake ( V˙O (2max)). We hypothesised that the extent of inter-subject variability in the physiological responses to exercise would be greater when work rates were prescribed using % V˙O (2max) as compared to % 'delta' (Δ), a method of normalising exercise intensity in which both the gas exchange threshold (GET) and the V˙O (2max) are considered. 9 men completed a ramp incremental test on a cycle ergometer to establish the GET and V˙O (2max). Subsequently, subjects completed 6 constant-work-rate exercise bouts at intensities corresponding to: 50%, 70% and 90% V˙O (2max); and 60% GET, 40% Δ (that is, 40% of the difference between the GET and V˙O (2max)) and 80% Δ. For all bouts, exercise was continued for 20 min or until task failure if this occurred sooner. When exercise was prescribed using the % Δ concept, there were significant reductions in the inter-subject variability in pulmonary gas exchange, blood lactate accumulation, heart rate, and ratings of perceived exertion (all P < 0.05). In conclusion, the % Δ concept resulted in more consistent inter-subject physiological responses to constant-work-rate exercise and should be used in preference to % V˙O (2max) to more effectively normalise exercise intensity.
Abstract.
Author URL.
Jones AM, Haramizu S, Ranchordas M, Burke L, Stear S, Castell LM (2011). A-Z of nutritional supplements: dietary supplements, sports nutrition foods and ergogenic aids for health and performance--Part 27.
Br J Sports Med,
45(15), 1246-1248.
Author URL.
Lansley KE, Winyard PG, Bailey SJ, Vanhatalo A, Wilkerson DP, Blackwell JR, Gilchrist M, Benjamin N, Jones AM (2011). Acute dietary nitrate supplementation improves cycling time trial performance.
Med Sci Sports Exerc,
43(6), 1125-1131.
Abstract:
Acute dietary nitrate supplementation improves cycling time trial performance.
PURPOSE: Dietary nitrate supplementation has been shown to reduce the O2 cost of submaximal exercise and to improve high-intensity exercise tolerance. However, it is presently unknown whether it may enhance performance during simulated competition. The present study investigated the effects of acute dietary nitrate supplementation on power output (PO), VO2, and performance during 4- and 16.1-km cycling time trials (TT). METHODS: After familiarization, nine club-level competitive male cyclists were assigned in a randomized, crossover design to consume 0.5 L of beetroot juice (BR; containing ∼ 6.2 mmol of nitrate) or 0.5 L of nitrate-depleted BR (placebo, PL; containing ∼ 0.0047 mmol of nitrate), ∼ 2.5 h before the completion of a 4- and a 16.1-km TT. RESULTS: BR supplementation elevated plasma [nitrite] (PL = 241 ± 125 vs BR = 575 ± 199 nM, P < 0.05). The VO2 values during the TT were not significantly different between the BR and PL conditions at any elapsed distance (P > 0.05), but BR significantly increased mean PO during the 4-km (PL = 279 ± 51 vs BR = 292 ± 44 W, P < 0.05) and 16.1-km TT (PL = 233 ± 43 vs BR = 247 ± 44 W, P < 0.01). Consequently, BR improved 4-km performance by 2.8% (PL = 6.45 ± 0.42 vs BR = 6.27 ± 0.35 min, P < 0.05) and 16.1-km performance by 2.7% (PL = 27.7 ± 2.1 vs BR = 26.9 ± 1.8 min, P < 0.01). CONCLUSIONS: These results suggest that acute dietary nitrate supplementation with 0.5 L of BR improves cycling economy, as demonstrated by a higher PO for the same VO2 and enhances both 4- and 16.1-km cycling TT performance.
Abstract.
Author URL.
Fudge BW, Spilsbury K, Ingham SA, Pringle JS, Jones AM (2011). Altitude Training May Improve Subsequent Endurance Performance in Elite Runners.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
43(5), 81-82.
Author URL.
Vanhatalo A, Jones AM, Burnley M (2011). Application of critical power in sport.
Int J Sports Physiol Perform,
6(1), 128-136.
Abstract:
Application of critical power in sport.
The critical power (CP) is mathematically defined as the power-asymptote of the hyperbolic relationship between power output and time-to-exhaustion. Physiologically, the CP represents the boundary between the steady-state and nonsteady state exercise intensity domains and therefore may provide a more meaningful index of performance than other well-known landmarks of aerobic fitness such as the lactate threshold and the maximal O2 uptake. Despite the potential importance to sports performance, the CP is often misinterpreted as a purely mathematical construct which lacks physiological meaning and only in recent years has this concept begun to emerge as valid and useful technique for monitoring endurance fitness. This commentary defines the basic principles of the CP concept, outlines its importance to high-intensity exercise performance, and provides an overview of the current methods available for its assessment. Interventions including training, pacing and prior exercise can be used to alter the parameters of the power-time relationship. A future challenge lies in optimizing such interventions in order to positively affect the parameters of the power-time relationship and thereby enhance sports performance in specific events.
Abstract.
Author URL.
Vanhatalo A, Fulford J, Bailey SJ, Blackwell JR, Winyard PG, Jones AM (2011). Dietary nitrate reduces muscle metabolic
perturbation and improves exercise tolerance in
hypoxia.
Journal of PhysiologyAbstract:
Dietary nitrate reduces muscle metabolic
perturbation and improves exercise tolerance in
hypoxia
Exercise in hypoxia is associated with reduced muscle oxidative function and impaired
exercise tolerance. We hypothesised that dietary nitrate supplementation (which increases
plasma [nitrite] and thus NO bioavailability) would ameliorate the adverse effects of hypoxia
on muscle metabolism and oxidative function. In a double-blind, randomised crossover study,
nine healthy subjects completed knee-extension exercise to the limit of tolerance (Tlim), once
in normoxia (20.9% O2; CON) and twice in hypoxia (14.5% O2). During 24 h prior to the
hypoxia trials, subjects consumed 0.75 L of nitrate-rich beetroot juice (9.3 mmol nitrate; HBR)
or 0.75 L of nitrate-depleted beetroot juice as a placebo (0.006 mmol nitrate; H-PL).
Muscle metabolism was assessed using calibrated 31P-MRS. Plasma [nitrite] was elevated
(P
Abstract.
Lansley KE, Winyard PG, Fulford J, Vanhatalo A, Bailey SJ, Blackwell JR, DiMenna FJ, Gilchrist M, Benjamin N, Jones AM, et al (2011). Dietary nitrate supplementation reduces the O2 cost of walking and running: a placebo-controlled study.
J Appl Physiol (1985),
110(3), 591-600.
Abstract:
Dietary nitrate supplementation reduces the O2 cost of walking and running: a placebo-controlled study.
Dietary supplementation with beetroot juice (BR) has been shown to reduce resting blood pressure and the O(2) cost of submaximal exercise and to increase tolerance to high-intensity cycling. We tested the hypothesis that the physiological effects of BR were consequent to its high NO(3)(-) content per se, and not the presence of other potentially bioactive compounds. We investigated changes in blood pressure, mitochondrial oxidative capacity (Q(max)), and physiological responses to walking and moderate- and severe-intensity running following dietary supplementation with BR and NO(3)(-)-depleted BR [placebo (PL)]. After control (nonsupplemented) tests, nine healthy, physically active male subjects were assigned in a randomized, double-blind, crossover design to receive BR (0.5 l/day, containing ∼6.2 mmol of NO(3)(-)) and PL (0.5 l/day, containing ∼0.003 mmol of NO(3)(-)) for 6 days. Subjects completed treadmill exercise tests on days 4 and 5 and knee-extension exercise tests for estimation of Q(max) (using (31)P-magnetic resonance spectroscopy) on day 6 of the supplementation periods. Relative to PL, BR elevated plasma NO(2)(-) concentration (183 ± 119 vs. 373 ± 211 nM, P < 0.05) and reduced systolic blood pressure (129 ± 9 vs. 124 ± 10 mmHg, P < 0.01). Q(max) was not different between PL and BR (0.93 ± 0.05 and 1.05 ± 0.22 mM/s, respectively). The O(2) cost of walking (0.87 ± 0.12 and 0.70 ± 0.10 l/min in PL and BR, respectively, P < 0.01), moderate-intensity running (2.26 ± 0.27 and 2.10 ± 0.28 l/min in PL and BR, respectively, P < 0.01), and severe-intensity running (end-exercise O(2) uptake = 3.77 ± 0.57 and 3.50 ± 0.62 l/min in PL and BL, respectively, P < 0.01) was reduced by BR, and time to exhaustion during severe-intensity running was increased by 15% (7.6 ± 1.5 and 8.7 ± 1.8 min in PL and BR, respectively, P < 0.01). In contrast, relative to control, PL supplementation did not alter plasma NO(2)(-) concentration, blood pressure, or the physiological responses to exercise. These results indicate that the positive effects of 6 days of BR supplementation on the physiological responses to exercise can be ascribed to the high NO(3)(-) content per se.
Abstract.
Author URL.
Stellingwerff T, Jeukendrup AE (2011). Don't forget the gut--it is an important athletic organ!.
J Appl Physiol (1985),
110(1).
Author URL.
Davies RC, Rowlands AV, Poole DC, Jones AM, Eston RG (2011). Eccentric exercise-induced muscle damage dissociates the lactate and gas exchange thresholds.
J Sports Sci,
29(2), 181-189.
Abstract:
Eccentric exercise-induced muscle damage dissociates the lactate and gas exchange thresholds.
We tested the hypothesis that exercise-induced muscle damage would increase the ventilatory (V(E)) response to incremental/ramp cycle exercise (lower the gas exchange threshold) without altering the blood lactate profile, thereby dissociating the gas exchange and lactate thresholds. Ten physically active men completed maximal incremental cycle tests before (pre) and 48 h after (post) performing eccentric exercise comprising 100 squats. Pulmonary gas exchange was measured breath-by-breath and fingertip blood sampled at 1-min intervals for determination of blood lactate concentration. The gas exchange threshold occurred at a lower work rate (pre: 136 ± 27 W; post: 105 ± 19 W; P < 0.05) and oxygen uptake (VO(2)) (pre: 1.58 ± 0.26 litres · min(-1); post: 1.41 ± 0.14 litres · min(-1); P < 0.05) after eccentric exercise. However, the lactate threshold occurred at a similar work rate (pre: 161 ± 19 W; post: 158 ± 22 W; P > 0.05) and VO(2) (pre: 1.90 ± 0.20 litres · min(-1); post: 1.88 ± 0.15 litres · min(-1); P > 0.05) after eccentric exercise. These findings demonstrate that exercise-induced muscle damage dissociates the V(E) response to incremental/ramp exercise from the blood lactate response, indicating that V(E) may be controlled by additional or altered neurogenic stimuli following eccentric exercise. Thus, due consideration of prior eccentric exercise should be made when using the gas exchange threshold to provide a non-invasive estimation of the lactate threshold.
Abstract.
Author URL.
Davies R, Rowlands AV, Jones AM, Eston RG (2011). Eccentric exercise-induced muscle damage dissociates the lactate and gas exchange thresholds.
Journal of Sports Sciences,
29, 181-189.
Abstract:
Eccentric exercise-induced muscle damage dissociates the lactate and gas exchange thresholds.
We tested the hypothesis that exercise-induced muscle damage (EIMD) would increase the ventilatory response to incremental/ramp cycle exercise (lower the gas exchange threshold), without altering the blood lactate profile thereby dissociating the gas exchange and lactate thresholds. Ten physically active men completed maximal incremental cycle tests before (pre) and 48 h after (post) performing eccentric exercise comprising 100 squats. Pulmonary gas exchange was measured breath-by-breath and finger-tip blood sampled at 1-min intervals for blood [La] determination. The gas exchange threshold occurred at a lower work rate (pre, 136 ± 27 W; post, 105 ± 19 W, P< 0.05) and. (pre, 1.58 + 0.26; post, 1.41 + 0.14 l.min-1, P< 0.05) after eccentric exercise. However, the lactate threshold occurred at a similar work rate (pre, 161 ± 19 W; post, 158 ± 22 W, P> 0.05) and. (pre, 1.90 ± 0.20 l.min-1; post, 1.88 ± 0.15 l.min-1, P > 0.05) after eccentric exercise. These findings demonstrate that EIMD dissociates the response to incremental/ramp exercise from the [La] response indicating that may be controlled by additional or altered neurogenic stimuli following eccentric exercise. Thus, due consideration of prior eccentric exercise should be made when using the gas exchange threshold to provide a non-invasive estimation of the lactate threshold.
Abstract.
Barker AR, Williams CA, Jones AM, Armstrong N (2011). Establishing maximal oxygen uptake in young people during a ramp cycle test to exhaustion.
Br J Sports Med,
45(6), 498-503.
Abstract:
Establishing maximal oxygen uptake in young people during a ramp cycle test to exhaustion.
OBJECTIVES: This study tested the hypotheses that (1) secondary criteria (respiratory exchange ratio (RER), heart rate, blood [lactate]) traditionally used to verify the determination of maximum oxygen uptake (VO₂(max)) in children can result in the acceptance of a 'submaximal' VO₂(max) or falsely reject a 'true' VO(₂max) and (2) the VO₂(peak) recorded during a ramp test in children is comparable to the VO₂(peak) achieved during supramaximal testing. METHODS: Thirteen children (9-10 years) completed a ramp cycle test to exhaustion to determine their VO₂(peak). After 15 min of recovery, the participants performed a supramaximal cycle test to exhaustion at 105% of their ramp test peak power. RESULTS: Compared with the VO₂(peak) during the ramp test, a significantly lower VO₂ was recorded at a RER of 1.00 (1.293 litre/min (SD 0.265) vs 1.681 litre/min (SD 0.295), p < 0.001, n = 12), at a heart rate of 195 beats/min (1.556 litre/min (SD 0.265) vs 1.721 litre/min (SD 0.318), p < 0.001, n = 10) and at 85% of age-predicted maximum (1.345 litre/min (SD 0.228) vs 1.690 litre/min (SD 0.284), p < 0.001, n = 13). Supramaximal testing yielded a VO₂(peak) that was not significantly different from the ramp test (1.615 litre/min (SD 0.307) vs 1.690 litre/min (SD 0.284), p = 0.090, respectively). CONCLUSIONS: the use of secondary criteria to verify a maximal effort in young people during ramp cycling exercise may result in the acceptance of a submaximal VO₂(max). As supramaximal testing elicits a VO₂(peak) similar to the ramp protocol, thus satisfying the plateau criterion, the use of such tests is recommended as the appropriate method of confirming a 'true' VO₂(max) with children.
Abstract.
Author URL.
Bailey SJ, Vanhatalo A, DiMenna FJ, Wilkerson DP, Jones AM (2011). Fast-start strategy improves VO2 kinetics and high-intensity exercise performance.
Med Sci Sports Exerc,
43(3), 457-467.
Abstract:
Fast-start strategy improves VO2 kinetics and high-intensity exercise performance.
PURPOSE: the purpose of this study was to investigate the influence of pacing strategy on pulmonary VO2 kinetics and performance during high-intensity exercise. METHODS: Seven males completed 3- and 6-min bouts of cycle exercise on three occasions with the bouts initiated using an even-start (ES; constant work rate), fast-start (FS), or slow-start (SS) pacing strategy. In all conditions, subjects completed an all-out sprint over the final 60 s of the test as a measure of performance. RESULTS: for the 3-min exercise bouts, the mean response time (MRT) for the VO2 kinetics over the pacing phase was shortest in FS (35 ± 6 s), longest in SS (55 ± 14 s), and intermediate in ES (41 ± 10 s) (P < 0.05 for all comparisons). For the 6-min bouts, the VO2 MRT was longer in SS (56 ± 15 s) than that in FS and ES (38 ± 7 and 42 ± 6 s, respectively, P < 0.05). The VO2 at the end of exercise was not different from the VO2max during the 6-min exercise bouts or 3-FS but was lower than VO2max for 3-ES and 3-SS (P < 0.05). The end-sprint performance was significantly enhanced in 3-FS compared with 3-ES and 3-SS (mean power = 374 ± 68 vs 348 ± 61 and 345 ± 71 W, respectively; P < 0.05). However, end-sprint performance was unaffected by pacing strategy in the 6-min bouts. CONCLUSIONS: These data indicate that an FS pacing strategy significantly improves performance during 3-min bouts of high-intensity exercise by speeding VO2 kinetics and enabling the attainment of VO2max.
Abstract.
Author URL.
Skiba PF, Jones AM (2011). Implications of the critical speed and slow component of Vo2 for the 2-hour marathon.
J Appl Physiol (1985),
110(1).
Author URL.
Simpson LP, Jones AM, Vanhatalo A, Wilkerson DP (2011). Influence of Fiber-specific Muscle Glycogen Depletion on the Parameters of the 3-min All-out Cycling Test.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
43(5), 774-774.
Author URL.
Bailey SJ, Winyard PG, Blackwell JR, Vanhatalo A, Lansley KE, Dimenna FJ, Wilkerson DP, Campbell IT, Jones AM (2011). Influence of N-acetylcysteine administration on pulmonary O₂ uptake kinetics and exercise tolerance in humans.
Respir Physiol Neurobiol,
175(1), 121-129.
Abstract:
Influence of N-acetylcysteine administration on pulmonary O₂ uptake kinetics and exercise tolerance in humans.
We investigated the influence of the antioxidant N-acetylcysteine (NAC) on plasma nitrite concentration ([NO₂⁻]), pulmonary oxygen uptake (V(O₂)) kinetics and exercise tolerance. Eight males completed 'step' moderate- and severe-intensity cycle exercise tests following infusion of either NAC (125 mg kg⁻¹ h⁻¹ for 15 min followed by 25 mg kg⁻¹ h⁻¹ until the termination of exercise) or Placebo (PLA; saline). Following the initial loading phase, NAC infusion elevated plasma free sulfhydryl groups compared to placebo (PLA: 4 ± 2 vs. NAC: 13 ± 3 μ M g⁻¹; P < 0.05) and this elevation was preserved throughout the protocol. The administration of NAC did not significantly influence plasma [NO₂⁻] or V(O₂) kinetics during either moderate- or severe-intensity exercise. Although NAC did not significantly alter severe-intensity exercise tolerance at the group mean level (PLA: 776 ± 181 vs. NAC: 878 ± 284 s; P > 0.05), there was appreciable inter-subject variability in the response: four subjects had small reductions in exercise tolerance with NAC compared to PLA (-4%, -8%, -11%, and -14%) while the other four showed substantial improvements (+24%, +24%, +40%, and +69%). The results suggest that exercise-induced redox perturbations may contribute to fatigue development in recreationally-active adults.
Abstract.
Author URL.
McNarry MA, Welsman JR, Jones AM (2011). Influence of training and maturity status on the cardiopulmonary responses to ramp incremental cycle and upper body exercise in girls.
J Appl Physiol (1985),
110(2), 375-381.
Abstract:
Influence of training and maturity status on the cardiopulmonary responses to ramp incremental cycle and upper body exercise in girls.
It has been suggested that the potential for training to alter the physiological responses to exercise in children is related to a "maturational threshold". To address this, we investigated the interaction of swim-training status and maturity on cardiovascular and metabolic responses to lower and upper body exercise. Twenty-one prepubertal [Pre: 11 trained (T), 10 untrained (UT)], 30 pubertal (Pub: 14 T, 16 UT), and 18 postpubertal (Post: 8 T, 10 UT) girls completed ramp incremental exercise on a cycle and an upper body ergometer. In addition to pulmonary gas exchange measurements, stroke volume and cardiac output were estimated by thoracic bioelectrical impedance, and muscle oxygenation status was assessed using near-infrared spectroscopy. All T girls had a higher peak O(2) uptake during cycle (Pre: T 49 ± 5 vs. UT 40 ± 4; Pub: T 46 ± 5 vs. UT 36 ± 4; Post: T 48 ± 5 vs. UT 39 ± 8 ml·kg(-1)·min(-1); all P < 0.05) and upper body exercise (Pre: T 37 ± 6 vs. UT 32 ± 5; Pub: T 36 ± 5 vs. UT 28 ± 5; Post: T 39 ± 3 vs. UT 28 ± 7 ml·kg(-1)·min(-1); all P < 0.05). T girls also had a higher peak cardiac output during both modalities, and this reached significance in Pub (cycle: T 21 ± 3 vs. UT 18 ± 3; upper body: T 20 ± 4 vs. UT 15 ± 4 l/min; all P < 0.05) and Post girls (cycle: T 21 ± 4 vs. UT 17 ± 2; upper body: T 22 ± 3 vs. UT 18 ± 2 l/min; all P < 0.05). None of the measured pulmonary, cardiovascular, or metabolic parameters interacted with maturity, and the magnitude of the difference between T and UT girls was similar, irrespective of maturity stage. These results challenge the notion that differences in training status in young people are only evident once a maturational threshold has been exceeded.
Abstract.
Author URL.
McNarry MA, Welsman JR, Jones AM (2011). Influence of training status and exercise modality on pulmonary O2 uptake kinetics in pubertal girls.
Eur J Appl Physiol,
111(4), 621-631.
Abstract:
Influence of training status and exercise modality on pulmonary O2 uptake kinetics in pubertal girls.
The influence of training status on the oxygen uptake (VO2) response to heavy intensity exercise in pubertal girls has not previously been investigated. We hypothesised that whilst training status-related adaptations would be evident in the VO2, heart rate (HR) and deoxyhaemoglobin ([HHb]) kinetics of pubertal swimmers during both lower and upper body exercise, they would be more pronounced during upper body exercise. Eight swim-trained (T; 14.2 ± 0.7 years) and eight untrained (UT; 14.5 ± 1.3 years) girls completed a number of constant-work-rate transitions on cycle and upper body ergometers at 40% of the difference between the gas exchange threshold and peak VO2. The phase II VO2 time constant (τ) was significantly shorter in the trained girls during both cycle (T: 21 ± 6 vs. UT: 35 ± 11 s; P < 0.01) and upper body exercise (T: 29 ± 8 vs. UT: 44 ± 8 s; P < 0.01). The VO2 slow component was not influenced by training status. The [HHb] τ was significantly shorter in the trained girls during both cycle (T: 12 ± 2 vs. UT: 20 ± 6 s; P < 0.01) and upper body exercise (T: 13 ± 3 vs. UT: 21 ± 7 s; P < 0.01), as was the HR τ (cycle, T: 36 ± 5 vs. UT: 53 ± 9 s; upper body, T: 32 ± 3 vs. UT: 43 ± 2; P < 0.01). This study suggests that both central and peripheral factors contribute to the faster VO2 kinetics in the trained girls and that differences are evident in both lower and upper body exercise.
Abstract.
Author URL.
Winyard PG, Ryan B, Eggleton P, Nissim A, Taylor E, Lo Faro ML, Burkholz T, Szabó-Taylor KE, Fox B, Viner N, et al (2011). Measurement and meaning of markers of reactive species of oxygen, nitrogen and sulfur in healthy human subjects and patients with inflammatory joint disease.
Biochem Soc Trans,
39(5), 1226-1232.
Abstract:
Measurement and meaning of markers of reactive species of oxygen, nitrogen and sulfur in healthy human subjects and patients with inflammatory joint disease.
Reactive species of oxygen, nitrogen and sulfur play cell signalling roles in human health, e.g. recent studies have shown that increased dietary nitrate, which is a source of RNS (reactive nitrogen species), lowers resting blood pressure and the oxygen cost of exercise. In such studies, plasma nitrite and nitrate are readily determined by chemiluminescence. At sites of inflammation, such as the joints of RA (rheumatoid arthritis) patients, the generation of ROS (reactive oxygen species) and RNS overwhelms antioxidant defences and one consequence is oxidative/nitrative damage to proteins. For example, in the inflamed joint, increased RNS-mediated protein damage has been detected in the form of a biomarker, 3-nitrotyrosine, by immunohistochemistry, Western blotting, ELISAs and MS. In addition to NO•, another cell-signalling gas produced in the inflamed joint is H2S (hydrogen sulfide), an RSS (reactive sulfur species). This gas is generated by inflammatory induction of H2S-synthesizing enzymes. Using zinc-trap spectrophotometry, we detected high (micromolar) concentrations of H2S in RA synovial fluid and levels correlated with clinical scores of inflammation and disease activity. What might be the consequences of the inflammatory generation of reactive species? Effects on inflammatory cell-signalling pathways certainly appear to be crucial, but in the current review we highlight the concept that ROS/RNS-mediated protein damage creates neoepitopes, resulting in autoantibody formation against proteins, e.g. type-II collagen and the complement component, C1q. These autoantibodies have been detected in inflammatory autoimmune diseases.
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Author URL.
Skiba PF, Chidnok W, Vanhatalo A, Jones AM (2011). Modeling Charge / Discharge Kinetics of the W' During Intermittent Exercise.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
43(5), 141-141.
Author URL.
Davies RC, Eston RG, Fulford J, Rowlands AV, Jones AM (2011). Muscle damage alters the metabolic response to dynamic exercise in humans: a 31P-MRS study.
J Appl Physiol (1985),
111(3), 782-790.
Abstract:
Muscle damage alters the metabolic response to dynamic exercise in humans: a 31P-MRS study.
We used ³¹P-magnetic resonance spectroscopy to test the hypothesis that exercise-induced muscle damage (EIMD) alters the muscle metabolic response to dynamic exercise, and that this contributes to the observed reduction in exercise tolerance following EIMD in humans. Ten healthy, physically active men performed incremental knee extensor exercise inside the bore of a whole body 1.5-T superconducting magnet before (pre) and 48 h after (post) performing 100 squats with a load corresponding to 70% of body mass. There were significant changes in all markers of muscle damage [perceived muscle soreness, creatine kinase activity (434% increase at 24 h), and isokinetic peak torque (16% decrease at 24 h)] following eccentric exercise. Muscle phosphocreatine concentration ([PCr]) and pH values during incremental exercise were not different pre- and post-EIMD (P > 0.05). However, resting inorganic phosphate concentration ([P(i)]; pre: 4.7 ± 0.8; post: 6.7 ± 1.7 mM; P < 0.01) and, consequently, [P(i)]/[PCr] values (pre: 0.12 ± 0.02; post: 0.18 ± 0.05; P < 0.01) were significantly elevated following EIMD. These mean differences were maintained during incremental exercise (P < 0.05). Time to exhaustion was significantly reduced following EIMD (519 ± 56 and 459 ± 63 s, pre- and post-EIMD, respectively, P < 0.001). End-exercise pH (pre: 6.75 ± 0.04; post: 6.83 ± 0.04; P < 0.05) and [PCr] (pre: 7.2 ± 1.7; post: 14.5 ± 2.1 mM; P < 0.01) were higher, but end-exercise [P(i)] was not significantly different (pre: 19.7 ± 1.9; post: 21.1 ± 2.6 mM, P > 0.05) following EIMD. The results indicate that alterations in phosphate metabolism, specifically the elevated [P(i)] at rest and throughout exercise, may contribute to the reduced exercise tolerance observed following EIMD.
Abstract.
Author URL.
Vanhatalo A, Poole DC, DiMenna FJ, Bailey SJ, Jones AM (2011). Muscle fiber recruitment and the slow component of O2 uptake: constant work rate vs. all-out sprint exercise.
Am J Physiol Regul Integr Comp Physiol,
300(3), R700-R707.
Abstract:
Muscle fiber recruitment and the slow component of O2 uptake: constant work rate vs. all-out sprint exercise.
The slow component of pulmonary O(2) uptake (Vo(2)) during constant work rate (CWR) high-intensity exercise has been attributed to the progressive recruitment of (type II) muscle fibers. We tested the following hypotheses: 1) the Vo(2) slow component gain would be greater in a 3-min all-out cycle test than in a work-matched CWR test, and 2) the all-out test would be associated with a progressive decline, and the CWR test with a progressive increase, in muscle activation, as estimated from the electromyogram (EMG) of the vastus lateralis muscle. Eight men (aged 21-39 yr) completed a ramp incremental test, a 3-min all-out test, and a work- and time-matched CWR test to exhaustion. The maximum Vo(2) attained in an initial ramp incremental test (3.97 ± 0.83 l/min) was reached in both experimental tests (3.99 ± 0.84 and 4.03 ± 0.76 l/min for all-out and CWR, respectively). The Vo(2) slow component was greater (P < 0.05) in the all-out test (1.21 ± 0.31 l/min, 4.2 ± 2.2 ml·min(-1)·W(-1)) than in the CWR test (0.59 ± 0.22 l/min, 1.70 ± 0.5 ml·min(-1)·W(-1)). The integrated EMG declined by 26% (P < 0.001) during the all-out test and increased by 60% (P < 0.05) during the CWR test from the first 30 s to the last 30 s of exercise. The considerable reduction in muscle efficiency in the all-out test in the face of a progressively falling integrated EMG indicates that progressive fiber recruitment is not requisite for development of the Vo(2) slow component during voluntary exercise in humans.
Abstract.
Author URL.
Haskell CF, Thompson K, Jones AM, Blackwell JR, Winyard PG, Forster J, Kennedy DO (2011). Nitrate-rich beetroot juice modulates cerebral blood flow and cognitive performance in humans. Appetite, 57(2), 560-560.
Wilkerson DP, Poole DC, Jones AM, Fulford J, Mawson DM, Ball CI, Shore AC (2011). Older type 2 diabetic males do not exhibit abnormal pulmonary oxygen uptake and muscle oxygen utilization dynamics during submaximal cycling exercise.
Am J Physiol Regul Integr Comp Physiol,
300(3), R685-R692.
Abstract:
Older type 2 diabetic males do not exhibit abnormal pulmonary oxygen uptake and muscle oxygen utilization dynamics during submaximal cycling exercise.
There are reports of abnormal pulmonary oxygen uptake (Vo(2)) and deoxygenated hemoglobin ([HHb]) kinetics in individuals with Type 2 diabetes (T2D) below 50 yr of age with disease durations of
Abstract.
Author URL.
Jones AM, Bailey SJ, Vanhatalo A, Fulford J, Gilchrist M, Benjamin N, Winyard PG (2011). Reply to Lundberg, Larsen, and Weitzberg.
J Appl Physiol (1985),
111(2).
Author URL.
Jones AM, Vanhatalo A, Burnley M, Morton RH, Poole DC (2011). Response. Med Sci Sports Exerc, 43(3).
Jones AM, Grassi B, Christensen PM, Krustrup P, Bangsbo J, Poole DC (2011). Slow component of VO2 kinetics: mechanistic bases and practical applications.
Med Sci Sports Exerc,
43(11), 2046-2062.
Abstract:
Slow component of VO2 kinetics: mechanistic bases and practical applications.
The V·O₂ slow component, a slowly developing increase in V·O₂ during constant-work-rate exercise performed above the lactate threshold, represents a progressive loss of skeletal muscle contractile efficiency and is associated with the fatigue process. This brief review outlines the current state of knowledge concerning the mechanistic bases of the V·O₂ slow component and describes practical interventions that can attenuate the slow component and thus enhance exercise tolerance. There is strong evidence that, during constant-work-rate exercise, the development of the V·O₂ slow component is associated with the progressive recruitment of additional (type II) muscle fibers that are presumed to have lower efficiency. Recent studies, however, indicate that muscle efficiency is also lowered (resulting in a "mirror-image" V·O₂ slow component) during fatiguing, high-intensity exercise in which additional fiber recruitment is unlikely or impossible. Therefore, it seems that muscle fatigue underpins the V·O₂ slow component, although the greater fatigue sensitivity of recruited type II fibers might still play a crucial role in the loss of muscle efficiency in both situations. Several interventions can reduce the magnitude of the V·O₂ slow component, and these are typically associated with an enhanced exercise tolerance. These include endurance training, inspiratory muscle training, priming exercise, dietary nitrate supplementation, and the inspiration of hyperoxic gas. All of these interventions reduce muscle fatigue development either by improving muscle oxidative capacity and thus metabolic stability or by enhancing bulk muscle O2 delivery or local Q·O₂-to-V·O₂ matching. Future honing of these interventions to maximize their impact on the V·O₂ slow component might improve sports performance in athletes and exercise tolerance in the elderly or in patient populations.
Abstract.
Author URL.
Mauger AR, Jones AM, Williams CA (2011). The effect of non-contingent and accurate performance feedback on pacing and time trial performance in 4-km track cycling.
Br J Sports Med,
45(3), 225-229.
Abstract:
The effect of non-contingent and accurate performance feedback on pacing and time trial performance in 4-km track cycling.
OBJECTIVE: to determine whether the provision of comparative performance feedback during 4 km track cycling affects completion time. DESIGN: Five highly trained male cyclists first performed a baseline (BL) 4-km time trial (TT) on a velodrome track, followed by two further randomised 4-km TT, during which riders received either correct (COR) or non-contingent (FAL) feedback based on their BL performance. RESULTS: Participants completed the COR TT in a significantly faster time (t(4)=-3.10, p
Abstract.
Author URL.
McNarry MA, Welsman JR, Jones AM (2011). The influence of training and maturity status on girls' responses to short-term, high-intensity upper- and lower-body exercise.
Appl Physiol Nutr Metab,
36(3), 344-352.
Abstract:
The influence of training and maturity status on girls' responses to short-term, high-intensity upper- and lower-body exercise.
A maturational threshold has been suggested to be present in young peoples' responses to exercise, with significant influences of training status evidenced only above this threshold. The presence of such a threshold has not been investigated for short-term, high-intensity exercise. To address this, we investigated the relationship between swim-training status and maturity on the power output, pulmonary gas exchange, and metabolic responses to an upper- and lower-body Wingate anaerobic test (WAnT). Girls at 3 stages of maturity participated:, prepubertal (Pre: 8 trained (T), 10 untrained (UT)), pubertal (Pub: 9 T, 15 UT), and postpubertal (Post: 8 T, 10 UT). At all maturity stages, T exhibited higher peak power (PP) and mean power (MP) during upper-body exercise (PP: Pre, T, 163 ± 20 vs. UT, 124 ± 29; Pub, T, 230 ± 42 vs. UT, 173 ± 41; Post, T, 245 ± 41 vs. UT, 190 ± 40 W; MP: Pre, T, 130 ± 23 vs. UT, 85 ± 26; Pub, T, 184 ± 37 vs. UT, 123 ± 38; Post, T, 200 ± 30 vs. UT, 150 ± 15 W; all p < 0.05) but not lower-body exercise, whilst the fatigue index was significantly lower in T for both exercise modalities. Irrespective of maturity, the oxidative contribution, calculated by the area under the oxygen uptake response profile, was not influenced by training status. No interaction was evident between training status and maturity, with similar magnitudes of difference between T and UT at all 3 maturity stages. These results suggest that there is no maturational threshold which must be surpassed for significant influences of training status to be manifest in the "anaerobic" exercise performance of young girls.
Abstract.
Author URL.
Burnley M, Jones AM (2010). "Traditional" perspectives can explain the sprint finish.
J Appl Physiol (1985),
108(2).
Author URL.
Bailey SJ, Winyard PG, Vanhatalo A, Blackwell JR, DiMenna FJ, Wilkerson DP, Jones AM (2010). Acute L-arginine supplementation reduces the O2 cost of moderate-intensity exercise and enhances high-intensity exercise tolerance.
J Appl Physiol (1985),
109(5), 1394-1403.
Abstract:
Acute L-arginine supplementation reduces the O2 cost of moderate-intensity exercise and enhances high-intensity exercise tolerance.
It has recently been reported that dietary nitrate (NO(3)(-)) supplementation, which increases plasma nitrite (NO(2)(-)) concentration, a biomarker of nitric oxide (NO) availability, improves exercise efficiency and exercise tolerance in healthy humans. We hypothesized that dietary supplementation with L-arginine, the substrate for NO synthase (NOS), would elicit similar responses. In a double-blind, crossover study, nine healthy men (aged 19-38 yr) consumed 500 ml of a beverage containing 6 g of l-arginine (Arg) or a placebo beverage (PL) and completed a series of "step" moderate- and severe-intensity exercise bouts 1 h after ingestion of the beverage. Plasma NO(2)(-) concentration was significantly greater in the Arg than the PL group (331 ± 198 vs. 159 ± 102 nM, P < 0.05) and systolic blood pressure was significantly reduced (123 ± 3 vs. 131 ± 5 mmHg, P < 0.01). The steady-state O(2) uptake (VO(2)) during moderate-intensity exercise was reduced by 7% in the Arg group (1.48 ± 0.12 vs. 1.59 ± 0.14 l/min, P < 0.05). During severe-intensity exercise, the Vo(2) slow component amplitude was reduced (0.58 ± 0.23 and 0.76 ± 0.29 l/min in Arg and PL, respectively, P < 0.05) and the time to exhaustion was extended (707 ± 232 and 562 ± 145 s in Arg and PL, respectively, P < 0.05) following consumption of Arg. In conclusion, similar to the effects of increased dietary NO(3)(-) intake, elevating NO bioavailability through dietary L-Arg supplementation reduced the O(2) cost of moderate-intensity exercise and blunted the VO(2) slow component and extended the time to exhaustion during severe-intensity exercise.
Abstract.
Author URL.
Vanhatalo A, Bailey SJ, Blackwell JR, DiMenna FJ, Pavey TG, Wilkerson DP, Benjamin N, Winyard PG, Jones AM (2010). Acute and chronic effects of dietary nitrate supplementation on blood pressure and the physiological responses to moderate-intensity and incremental exercise.
Am J Physiol Regul Integr Comp Physiol,
299(4), R1121-R1131.
Abstract:
Acute and chronic effects of dietary nitrate supplementation on blood pressure and the physiological responses to moderate-intensity and incremental exercise.
Dietary nitrate (NO(3)(-)) supplementation with beetroot juice (BR) over 4-6 days has been shown to reduce the O(2) cost of submaximal exercise and to improve exercise tolerance. However, it is not known whether shorter (or longer) periods of supplementation have similar (or greater) effects. We therefore investigated the effects of acute and chronic NO(3)(-) supplementation on resting blood pressure (BP) and the physiological responses to moderate-intensity exercise and ramp incremental cycle exercise in eight healthy subjects. Following baseline tests, the subjects were assigned in a balanced crossover design to receive BR (0.5 l/day; 5.2 mmol of NO(3)(-)/day) and placebo (PL; 0.5 l/day low-calorie juice cordial) treatments. The exercise protocol (two moderate-intensity step tests followed by a ramp test) was repeated 2.5 h following first ingestion (0.5 liter) and after 5 and 15 days of BR and PL. Plasma nitrite concentration (baseline: 454 ± 81 nM) was significantly elevated (+39% at 2.5 h postingestion; +25% at 5 days; +46% at 15 days; P < 0.05) and systolic and diastolic BP (baseline: 127 ± 6 and 72 ± 5 mmHg, respectively) were reduced by ∼4% throughout the BR supplementation period (P < 0.05). Compared with PL, the steady-state Vo(2) during moderate exercise was reduced by ∼4% after 2.5 h and remained similarly reduced after 5 and 15 days of BR (P < 0.05). The ramp test peak power and the work rate at the gas exchange threshold (baseline: 322 ± 67 W and 89 ± 15 W, respectively) were elevated after 15 days of BR (331 ± 68 W and 105 ± 28 W; P < 0.05) but not PL (323 ± 68 W and 84 ± 18 W). These results indicate that dietary NO(3)(-) supplementation acutely reduces BP and the O(2) cost of submaximal exercise and that these effects are maintained for at least 15 days if supplementation is continued.
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Jones AM, Vanhatalo A, Burnley M, Morton RH, Poole DC (2010). Critical power: implications for determination of V˙O2max and exercise tolerance.
Med Sci Sports Exerc,
42(10), 1876-1890.
Abstract:
Critical power: implications for determination of V˙O2max and exercise tolerance.
For high-intensity muscular exercise, the time-to-exhaustion (t) increases as a predictable and hyperbolic function of decreasing power (P) or velocity (V ). This relationship is highly conserved across diverse species and different modes of exercise and is well described by two parameters: the "critical power" (CP or CV), which is the asymptote for power or velocity, and the curvature constant (W') of the relationship such that t = W'/(P - CP). CP represents the highest rate of energy transduction (oxidative ATP production, V˙O2) that can be sustained without continuously drawing on the energy store W' (composed in part of anaerobic energy sources and expressed in kilojoules). The limit of tolerance (time t) occurs when W' is depleted. The CP concept constitutes a practical framework in which to explore mechanisms of fatigue and help resolve crucial questions regarding the plasticity of exercise performance and muscular systems physiology. This brief review presents the practical and theoretical foundations for the CP concept, explores rigorous alternative mathematical approaches, and highlights exciting new evidence regarding its mechanistic bases and its broad applicability to human athletic performance.
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Bailey SJ, Fulford J, Vanhatalo A, Winyard PG, Blackwell JR, DiMenna FJ, Wilkerson DP, Benjamin N, Jones AM (2010). Dietary nitrate supplementation enhances muscle contractile efficiency during knee-extensor exercise in humans.
J Appl Physiol (1985),
109(1), 135-148.
Abstract:
Dietary nitrate supplementation enhances muscle contractile efficiency during knee-extensor exercise in humans.
The purpose of this study was to elucidate the mechanistic bases for the reported reduction in the O(2) cost of exercise following short-term dietary nitrate (NO(3)(-)) supplementation. In a randomized, double-blind, crossover study, seven men (aged 19-38 yr) consumed 500 ml/day of either nitrate-rich beet root juice (BR, 5.1 mmol of NO(3)(-)/day) or placebo (PL, with negligible nitrate content) for 6 consecutive days, and completed a series of low-intensity and high-intensity "step" exercise tests on the last 3 days for the determination of the muscle metabolic (using (31)P-MRS) and pulmonary oxygen uptake (Vo(2)) responses to exercise. On days 4-6, BR resulted in a significant increase in plasma [nitrite] (mean +/- SE, PL 231 +/- 76 vs. BR 547 +/- 55 nM; P < 0.05). During low-intensity exercise, BR attenuated the reduction in muscle phosphocreatine concentration ([PCr]; PL 8.1 +/- 1.2 vs. BR 5.2 +/- 0.8 mM; P < 0.05) and the increase in Vo(2) (PL 484 +/- 41 vs. BR 362 +/- 30 ml/min; P < 0.05). During high-intensity exercise, BR reduced the amplitudes of the [PCr] (PL 3.9 +/- 1.1 vs. BR 1.6 +/- 0.7 mM; P < 0.05) and Vo(2) (PL 209 +/- 30 vs. BR 100 +/- 26 ml/min; P < 0.05) slow components and improved time to exhaustion (PL 586 +/- 80 vs. BR 734 +/- 109 s; P < 0.01). The total ATP turnover rate was estimated to be less for both low-intensity (PL 296 +/- 58 vs. BR 192 +/- 38 microM/s; P < 0.05) and high-intensity (PL 607 +/- 65 vs. BR 436 +/- 43 microM/s; P < 0.05) exercise. Thus the reduced O(2) cost of exercise following dietary NO(3)(-) supplementation appears to be due to a reduced ATP cost of muscle force production. The reduced muscle metabolic perturbation with NO(3)(-) supplementation allowed high-intensity exercise to be tolerated for a greater period of time.
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Author URL.
Bailey SJ, Fulford J, Vanhatalo A, Winyard PG, Blackwell JR, DiMenna FJ, Wilkerson DP, Benjamin N, Jones AM (2010). Dietary nitrate supplementation enhances muscle contractile efficiency during knee-extensor exercise in humans. (vol 109, pg 135, 2010).
JOURNAL OF APPLIED PHYSIOLOGY,
109(3), 943-943.
Author URL.
Vanhatalo A, McNaughton LR, Siegler J, Jones AM (2010). Effect of induced alkalosis on the power-duration relationship of "all-out" exercise.
Med Sci Sports Exerc,
42(3), 563-570.
Abstract:
Effect of induced alkalosis on the power-duration relationship of "all-out" exercise.
PURPOSE: We tested the hypotheses that sodium bicarbonate (NaHCO3) ingestion would result in no alteration in critical power (CP) but would improve performance in a 3-min all-out cycling test by increasing the total amount of work done above CP (W'). METHODS: Eight habitually active subjects completed 3-min all-out sprints against fixed resistance in a blind randomized design after a dose of 0.3 g.kg body mass of NaHCO3 and 0.045 g.kg body mass of sodium chloride (placebo; PL trial). Blood acid-base status was assessed from arterialized fingertip blood samples before and after exercise. The CP was calculated as the mean power output during the final 30 s of the test, and the W' was estimated as the power-time integral >CP. RESULTS: the NaHCO3 dose was effective in inducing preexercise alkalosis as indicated by changes in blood pH (PL = 7.40 +/- 0.02 vs NaHCO3 = 7.46 +/- 0.01, P < 0.001), [bicarbonate] (PL = 21.9 +/- 3.0 vs NaHCO3 = 29.0 +/- 3.8 mM, P < 0.05), and base excess (PL = -1.9 +/- 2.5 vs NaHCO3 = 5.0 +/- 3.0 mM, P < 0.05). There were no significant differences in the total work done (PL = 62.8 +/- 10.1 vs NaHCO3 = 62.7 +/- 10.1 kJ), the CP (PL = 248 +/- 50 vs NaHCO3 = 251 +/- 51 W), or the W' (PL = 18.2 +/- 6.4 vs NaHCO3 = 17.5 +/- 6.0 kJ) estimates between treatments. CONCLUSIONS: Despite notably enhanced blood-buffering capacity, NaHCO3 ingestion had no effect on the W', the CP, or the overall performance during 3 min of all-out cycling. It is concluded that preexercise blood alkalosis had no influence on the power-duration relationship for all-out exercise.
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Author URL.
Vanhatalo A, McNaughton LR, Seigler J, Jones AM (2010). Effect of induced alkalosis on the power-duration relationship of all-out exercise. Med Sci Sports Exerc, 3(42), 563-570.
DiMenna FJ, Bailey SJ, Vanhatalo A, Chidnok W, Jones AM (2010). Elevated baseline VO2 per se does not slow O2 uptake kinetics during work-to-work exercise transitions.
J Appl Physiol (1985),
109(4), 1148-1154.
Abstract:
Elevated baseline VO2 per se does not slow O2 uptake kinetics during work-to-work exercise transitions.
We investigated whether the characteristic slowing of pulmonary oxygen uptake (VO2) kinetics during "work-to-work" exercise is attributable to elevations in baseline metabolic rate (VO2) as opposed to the elevated baseline work rate, per se. We hypothesized that a step transition to a higher work rate from "unloaded" cycling, but with elevations in VO2 [and heart rate (HR)] reflective of a work-to-work transition, would result in a lengthened phase II time constant (τ(p)). Seven male subjects (mean ± SD age 27 ± 10 yr) completed 1) transitions to a high-intensity work rate from a moderate-intensity work rate (M→H) and 2) two consecutive bouts of high-intensity exercise (U→H and E→H, respectively) initiated from unloaded cycling, with the time separating the exercise bouts chosen such that the baseline VO2 for the second transition was similar to the baseline VO2 for the M→H transition. The τ(p) for M→H (48 ± 16 s) was significantly greater (P < 0.05) than the τ(p) for U→H (28 ± 8 s) and E→H (27 ± 6 s), which did not differ significantly. These findings suggest that the altered VO2 dynamics that are observed during work-to-work exercise are not related to the elevated baseline VO2 (or HR) per se; rather, these effects appear to be linked to the elevated baseline work rate, which would be expected to dictate the subsequent muscle fiber recruitment profile.
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Author URL.
Bailey SJ, Fulford J, Vanhatalo A, Winyard PG, Blackwell JR, DiMenna FJ, Wilkerson DP, Benjamin N, Jones AM (2010). Errtum: Dietary nitrate supplementation enhances muscle contractile efficiency during knee-extensor exercise in humans (Journal of Applied Physiology (2010) 109 (135-148)). Journal of Applied Physiology, 109(3).
Mauger AR, Jones AM, Williams CA (2010). Influence of acetaminophen on performance during time trial cycling.
J Appl Physiol (1985),
108(1), 98-104.
Abstract:
Influence of acetaminophen on performance during time trial cycling.
To establish whether acetaminophen improves performance of self-paced exercise through the reduction of perceived pain, 13 trained male cyclists performed a self-paced 10-mile (16.1 km) cycle time trial (TT) following the ingestion of either acetaminophen (ACT) or a placebo (PLA), administered in randomized double-blind design. TT were completed in a significantly faster time (t(12) = 2.55, P < 0.05) under the ACT condition (26 min 15 s +/- 1 min 36 s vs. 26 min 45 s +/- 2 min 2 s). Power output (PO) was higher during the middle section of the TT in the ACT condition, resulting in a higher mean PO (P < 0.05) (265 +/- 12 vs. 255 +/- 15 W). Blood lactate concentration (B[La]) and heart rate (HR) were higher in the ACT condition (B[La] = 6.1 +/- 2.9 mmol/l; HR = 87 +/- 7%max) than in the PLA condition (B[La] = 5.1 +/- 2.6 mmol/l; HR = 84 +/- 9%max) (P < 0.05). No significant difference in rating of perceived exertion (ACT = 15.5 +/- 0.2; PLA = 15.7 +/- 0.2) or perceived pain (ACT = 5.6 +/- 0.2; PLA = 5.5 +/- 0.2) (P > 0.05) was observed. Using acetaminophen, participants cycled at a higher mean PO, with an increased HR and B[La], but without changes in perceived pain or exertion. Consequently, completion time was significantly faster. These findings support the notion that exercise is regulated by pain perception, and increased pain tolerance can improve exercise capacity.
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DiMenna FJ, Bailey SJ, Jones AM (2010). Influence of body position on muscle deoxy[Hb+Mb] during ramp cycle exercise.
Respir Physiol Neurobiol,
173(2), 138-145.
Abstract:
Influence of body position on muscle deoxy[Hb+Mb] during ramp cycle exercise.
We used near-infrared spectroscopy (NIRS) to test the hypothesis that body position alters the sigmoidal response profile of muscle fractional O(2) extraction (estimated using deoxy[Hb+Mb]) during incremental cycle exercise. Seven male subjects (mean±SD age 32±13 years) completed a ramp incremental cycling test to exhaustion (30W/min) in both the supine and upright body positions. The sigmoidal (as opposed to hyperbolic) model that provided the better fit to deoxy[Hb+Mb] data during upright cycling was also present for the supine response; however, the slope of the sigmoid was increased (upright: 0.052±0.012 vs. supine: 0.090±0.036%⋅%P(peak)(-1); P
Abstract.
Author URL.
Mauger AR, Jones AM, Williams CA (2010). Influence of exercise variation on the retention of a pacing strategy.
EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY,
108(5), 1015-1023.
Author URL.
Vanhatalo A, Fulford J, DiMenna FJ, Jones AM (2010). Influence of hyperoxia on muscle metabolic responses and the power-duration relationship during severe-intensity exercise in humans: a 31P magnetic resonance spectroscopy study.
Exp Physiol,
95(4), 528-540.
Abstract:
Influence of hyperoxia on muscle metabolic responses and the power-duration relationship during severe-intensity exercise in humans: a 31P magnetic resonance spectroscopy study.
Severe-intensity constant-work-rate exercise results in the attainment of maximal oxygen uptake, but the muscle metabolic milieu at the limit of tolerance (T(lim)) for such exercise remains to be elucidated. We hypothesized that T(lim) during severe-intensity exercise would be associated with the attainment of consistently low values of intramuscular phosphocreatine ([PCr]) and pH, as determined using (31)P magnetic resonance spectroscopy, irrespective of the work rate and the inspired O(2) fraction. We also hypothesized that hyperoxia would increase the asymptote of the hyperbolic power-duration relationship (the critical power, CP) without altering the curvature constant (W). Seven subjects (mean +/- s.d. age 30 +/- 9 years) completed four constant-work-rate knee-extension exercise bouts to the limit of tolerance (range, 3-10 min) both in normoxia (N) and in hyperoxia (H; 70% O(2)) inside the bore of 1.5 T superconducting magnet. The [PCr] (approximately 5-10% of resting baseline) and pH (approximately 6.65) at the limit of tolerance during each of the four trials was not significantly different either in normoxia or in hyperoxia. At the same fixed work rate, the overall rate at which [PCr] fell with time was attenuated in hyperoxia (mean response time: N, 59 +/- 20 versus H, 116 +/- 46 s; P < 0.05). The CP was higher (N, 16.1 +/- 2.6 versus H, 18.0 +/- 2.3 W; P < 0.05) and the W was lower (N, 1.92 +/- 0.70 versus H, 1.48 +/- 0.31 kJ; P < 0.05) in hyperoxia compared with normoxia. These data indicate that T(lim) during severe-intensity exercise is associated with the attainment of consistently low values of muscle [PCr] and pH. The CP and W parameters of the power-duration relationship were both sensitive to the inspiration of hyperoxic gas.
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Dimenna FJ, Fulford J, Bailey SJ, Vanhatalo A, Wilkerson DP, Jones AM (2010). Influence of priming exercise on muscle [PCr] and pulmonary O2 uptake dynamics during 'work-to-work' knee-extension exercise.
Respir Physiol Neurobiol,
172(1-2), 15-23.
Abstract:
Influence of priming exercise on muscle [PCr] and pulmonary O2 uptake dynamics during 'work-to-work' knee-extension exercise.
Metabolic transitions from rest to high-intensity exercise were divided into two discrete steps (i.e. rest-to-moderate-intensity (R-->M) and moderate-to-high-intensity (M-->H)) to explore the effect of prior high-intensity 'priming' exercise on intramuscular [PCr] and pulmonary VO₂ kinetics for different sections of the motor unit pool. It was hypothesized that [PCr] and VO₂ kinetics would be unaffected by priming during R-->M exercise, but that the time constants (tau) describing the fundamental [PCr] response and the phase II VO₂ response would be significantly reduced by priming for M-->H exercise. On three separate occasions, six male subjects completed two identical R-->M/M-->H 'work-to-work' prone knee-extension exercise bouts separated by 5min rest. Two trials were performed with measurement of pulmonary VO₂ and the integrated electromyogram (iEMG) of the right m. vastus lateralis. The third trial was performed within the bore of a 1.5-T superconducting magnet for (31)P-MRS assessment of muscle metabolic responses. Priming did not significantly affect the [PCr] or VO₂ tau during R-->M ([PCr] tau Unprimed: 24+/-16 vs. Primed: 22+/-14s; VO₂ tau Unprimed: 26+/-8 vs. Primed: 25+/-9s) or M-->H transitions ([PCr] tau Unprimed: 30+/-5 vs. Primed: 32+/-7s; VO₂ tau Unprimed: 37+/-5 vs. Primed: 38+/-9s). However, it did reduce the amplitudes of the [PCr] and VO₂ slow components by 50% and 46%, respectively, during M-->H (PH exercise after priming. It is concluded that the tau for the initial exponential change of muscle [PCr] and pulmonary VO₂ following the transition from moderate-to-high-intensity prone knee-extension exercise is not altered by priming exercise.
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Winlove MA, Jones AM, Welsman JR (2010). Influence of training status and exercise modality on pulmonary O(2) uptake kinetics in pre-pubertal girls.
Eur J Appl Physiol,
108(6), 1169-1179.
Abstract:
Influence of training status and exercise modality on pulmonary O(2) uptake kinetics in pre-pubertal girls.
The limited available evidence suggests that endurance training does not influence the pulmonary oxygen uptake (V(O)(2)) kinetics of pre-pubertal children. We hypothesised that, in young trained swimmers, training status-related adaptations in the V(O)(2) and heart rate (HR) kinetics would be more evident during upper body (arm cranking) than during leg cycling exercise. Eight swim-trained (T; 11.4 +/- 0.7 years) and eight untrained (UT; 11.5 +/- 0.6 years) girls completed repeated bouts of constant work rate cycling and upper body exercise at 40% of the difference between the gas exchange threshold and peak V(O)(2). The phase II V(O)(2) time constant was significantly shorter in the trained girls during upper body exercise (T: 25 +/- 3 vs. UT: 37 +/- 6 s; P < 0.01), but no training status effect was evident in the cycle response (T: 25 +/- 5 vs. UT: 25 +/- 7 s). The V(O)(2) slow component amplitude was not affected by training status or exercise modality. The time constant of the HR response was significantly faster in trained girls during both cycle (T: 31 +/- 11 vs. UT: 47 +/- 9 s; P < 0.01) and upper body (T: 33 +/- 8 vs. UT: 43 +/- 4 s; P < 0.01) exercise. The time constants of the phase II V(O)(2)and HR response were not correlated regardless of training status or exercise modality. This study demonstrates for the first time that swim-training status influences upper body V(O)(2) kinetics in pre-pubertal children, but that cycle ergometry responses are insensitive to such differences.
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Bailey SJ, Romer LM, Kelly J, Wilkerson DP, DiMenna FJ, Jones AM (2010). Inspiratory muscle training enhances pulmonary O(2) uptake kinetics and high-intensity exercise tolerance in humans.
J Appl Physiol (1985),
109(2), 457-468.
Abstract:
Inspiratory muscle training enhances pulmonary O(2) uptake kinetics and high-intensity exercise tolerance in humans.
Fatigue of the respiratory muscles during intense exercise might compromise leg blood flow, thereby constraining oxygen uptake (Vo(2)) and limiting exercise tolerance. We tested the hypothesis that inspiratory muscle training (IMT) would reduce inspiratory muscle fatigue, speed Vo(2) kinetics and enhance exercise tolerance. Sixteen recreationally active subjects (mean + or - SD, age 22 + or - 4 yr) were randomly assigned to receive 4 wk of either pressure threshold IMT [30 breaths twice daily at approximately 50% of maximum inspiratory pressure (MIP)] or sham treatment (60 breaths once daily at approximately 15% of MIP). The subjects completed moderate-, severe- and maximal-intensity "step" exercise transitions on a cycle ergometer before (Pre) and after (Post) the 4-wk intervention period for determination of Vo(2) kinetics and exercise tolerance. There were no significant changes in the physiological variables of interest after Sham. After IMT, baseline MIP was significantly increased (Pre vs. Post: 155 + or - 22 vs. 181 + or - 21 cmH(2)O; P < 0.001), and the degree of inspiratory muscle fatigue was reduced after severe- and maximal-intensity exercise. During severe exercise, the Vo(2) slow component was reduced (Pre vs. Post: 0.60 + or - 0.20 vs. 0.53 + or - 0.24 l/min; P < 0.05) and exercise tolerance was enhanced (Pre vs. Post: 765 + or - 249 vs. 1,061 + or - 304 s; P < 0.01). Similarly, during maximal exercise, the Vo(2) slow component was reduced (Pre vs. Post: 0.28 + or - 0.14 vs. 0.18 + or - 0.07 l/min; P < 0.05) and exercise tolerance was enhanced (Pre vs. Post: 177 + or - 24 vs. 208 + or - 37 s; P < 0.01). Four weeks of IMT, which reduced inspiratory muscle fatigue, resulted in a reduced Vo(2) slow-component amplitude and an improved exercise tolerance during severe- and maximal-intensity exercise. The results indicate that the enhanced exercise tolerance observed after IMT might be related, at least in part, to improved Vo(2) dynamics, presumably as a consequence of increased blood flow to the exercising limbs.
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DiMenna FJ, Wilkerson DP, Burnley M, Bailey SJ, Jones AM (2010). Priming exercise speeds pulmonary O2 uptake kinetics during supine "work-to-work" high-intensity cycle exercise.
J Appl Physiol (1985),
108(2), 283-292.
Abstract:
Priming exercise speeds pulmonary O2 uptake kinetics during supine "work-to-work" high-intensity cycle exercise.
We manipulated the baseline metabolic rate and body position to explore the effect of the interaction between recruitment of discrete sections of the muscle fiber pool and muscle O(2) delivery on pulmonary O(2) uptake (VO(2)) kinetics during cycle exercise. We hypothesized that phase II VO(2) kinetics (tau(p)) in the transition from moderate- to severe-intensity exercise would be significantly slower in the supine than upright position because of a compromise to muscle perfusion and that a priming bout of severe-intensity exercise would return tau(p) during supine exercise to tau(p) during upright exercise. Eight male subjects [35 +/- 13 (SD) yr] completed a series of "step" transitions to severe-intensity cycle exercise from an "unloaded" (20-W) baseline and a baseline of moderate-intensity exercise in the supine and upright body positions. tau(p) was not significantly different between supine and upright exercise during transitions from a 20-W baseline to moderate- or severe-intensity exercise but was significantly greater during moderate- to severe-intensity exercise in the supine position (54 +/- 19 vs. 38 +/- 10 s, P < 0.05). Priming significantly reduced tau(p) during moderate- to severe-intensity supine exercise (34 +/- 9 s), returning it to a value that was not significantly different from tau(p) in the upright position. This effect occurred in the absence of changes in estimated muscle fractional O(2) extraction (from the near-infrared spectroscopy-derived deoxygenated Hb concentration signal), such that the priming-induced facilitation of muscle blood flow matched increased O(2) utilization in the recruited fibers, resulting in a speeding of VO(2) kinetics. These findings suggest that, during supine cycling, priming speeds VO(2) kinetics by providing an increased driving pressure for O(2) diffusion in the higher-order (i.e. type II) fibers, which would be recruited in the transition from moderate- to severe-intensity exercise and are known to be especially sensitive to limitations in O(2) supply.
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Burnley M, Vanhatalo A, Fulford J, Jones AM (2010). Similar metabolic perturbations during all-out and constant force exhaustive exercise in humans: a (31)P magnetic resonance spectroscopy study.
Exp Physiol,
95(7), 798-807.
Abstract:
Similar metabolic perturbations during all-out and constant force exhaustive exercise in humans: a (31)P magnetic resonance spectroscopy study.
It is not possible to attain a metabolic steady state during exercise above the so-called critical force or critical power. We tested the hypothesis that the muscle metabolic perturbations at the end of a bout of maximal isometric contractions, which yield a stable end-test force (equal to the critical force), would be similar to that at task failure following submaximal contractions performed above the critical force. Eight healthy subjects (four female) performed isometric single knee-extension exercise in the bore of a 1.5 T superconducting magnet on two occasions. Following familiarization, subjects performed the following exercises: (1) 60 maximal contractions (3 s contraction, 2 s rest); and (2) submaximal contractions (the same contraction regime performed at 54 +/- 8% maximal voluntary contraction) to task failure. Phosphocreatine (PCr), inorganic phosphate (P(i)) and diprotonated phosphate (H(2)PO(4)()) concentrations and pH were determined using (31)P magnetic resonance spectroscopy throughout both tests. During the maximal contractions, force production fell from 213 +/- 33 N to reach a plateau in the last 30 s of the test at 100 +/- 20 N. The muscle metabolic responses at the end of each test were substantial, but not different between conditions: [PCr] was reduced (to 21 +/- 12 and 17 +/- 7% of baseline for maximal and submaximal contractions, respectively; P = 0.17), [P(i)] was elevated (to 364 +/- 98 and 363 +/- 135% of baseline, respectively; P = 0.98) and pH reduced (to 6.64 +/- 0.16 and 6.69 +/- 0.17, respectively; P = 0.43). The [H(2)PO(4)()] was also elevated at the end of both tests (to 607 +/- 252 and 556 +/- 269% of baseline, respectively; P = 0.22). These data suggest that the exercise-induced metabolic perturbations contributing to force depression in all-out exercise are the same as those contributing to task failure during submaximal contractions.
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Author URL.
Barker AR, Jones AM, Armstrong N (2010). The influence of priming exercise on oxygen uptake, cardiac output, and muscle oxygenation kinetics during very heavy-intensity exercise in 9- to 13-yr-old boys.
J Appl Physiol (1985),
109(2), 491-500.
Abstract:
The influence of priming exercise on oxygen uptake, cardiac output, and muscle oxygenation kinetics during very heavy-intensity exercise in 9- to 13-yr-old boys.
The present study examined the effect of priming exercise on O(2) uptake (Vo(2)) kinetics during subsequent very heavy exercise in eight 9- to 13-yr-old boys. We hypothesised that priming exercise would 1) elevate muscle O(2) delivery prior to the subsequent bout of very heavy exercise, 2) have no effect on the phase II Vo(2) tau, 3) elevate the phase II Vo(2) total amplitude, and 4) reduce the magnitude of the Vo(2) slow component. Each participant completed repeat 6-min bouts of very heavy-intensity cycling exercise separated by 6 min of light pedaling. During the tests Vo(2), muscle oxygenation (near infrared spectroscopy), and cardiac output (Q) (thoracic impedance) were determined. Priming exercise increased baseline muscle oxygenation and elevated Q at baseline and throughout the second exercise bout. The phase II Vo(2) tau was not altered by priming exercise (bout 1: 22 + or - 7 s vs. bout 2: 20 + or - 4 s; P = 0.30). However, the time constant describing the entire Vo(2) response from start to end of exercise was accelerated (bout 1: 43 + or - 8 s vs. bout 2: 36 + or - 5 s; P = 0.002) due to an increased total phase II Vo(2) amplitude (bout 1: 1.73 + or - 0.33 l/min vs. bout 2: 1.80 + or - 0.59 l/min; P = 0.002) and a reduced Vo(2) slow component amplitude (bout 1: 0.18 + or - 0.08 l/min vs. bout 2: 0.12 + or - 0.09 l/min; P = 0.048). These results suggest that phase II Vo(2) kinetics in young boys is principally limited by intrinsic muscle metabolic factors, whereas the Vo(2) total phase II and slow component amplitudes may be O(2) delivery sensitive.
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DiMenna FJ, Jones AM (2009). "Linear" Versus "Nonlinear" O<inf>2</inf> Responses to Exercise: Reshaping Traditional Beliefs.
Journal of Exercise Science and Fitness,
7(2), 67-84.
Abstract:
"Linear" Versus "Nonlinear" O2 Responses to Exercise: Reshaping Traditional Beliefs
A number of basic tenets in traditional exercise physiology have been formulated on the assumption that pulmonary oxygen uptake ({A figure is presented}O2) adapts to changes in metabolic rate with linear, first-order response kinetics. However, questions regarding this premise have been raised for over half a century and clear contradictions have been reported. Specifically, Boltzmann's principle of superposition that defines linearity is violated for exercise transitions of different magnitudes, and the symmetry between on- and off-responses that first-order kinetics implies is not always present. Furthermore, a single exponential model does not adequately describe the {A figure is presented}O2 response to high-intensity exercise because a supplementary response compartment of delayed onset is manifest. Collectively, these findings reflect a range of nonlinear behaviors that indicate greater complexity of the {A figure is presented}O2 response, and it is imperative that these deviations be universally recognized, both to reshape our interpretation of the acute metabolic adaptation to exercise and also to provide clues regarding cellular mechanisms of respiratory control. © 2009 Elsevier (Singapore) Pte Ltd. All rights reserved.
Abstract.
Benjamin N, Bailey SJ, Vanhatalo A, Winyard P, Jones AM (2009). Beware of the pickle: health effects of nitrate intake Reply.
JOURNAL OF APPLIED PHYSIOLOGY,
107(5), 1678-1678.
Author URL.
Jones AM (2009). Comments on point: counterpoint: the kinetics of oxygen uptake during muscular exercise do/do not manifest time-delayed phase. Delays and their determinants. Journal of applied physiology (Bethesda, Md. : 1985), 107(5).
Jones AM (2009). Delays and their determinants. Journal of Applied Physiology, 107(5).
Bailey SJ, Winyard P, Vanhatalo A, Blackwell JR, Dimenna FJ, Wilkerson DP, Tarr J, Benjamin N, Jones AM (2009). Dietary nitrate supplementation reduces the O2 cost of low-intensity exercise and enhances tolerance to high-intensity exercise in humans.
J Appl Physiol (1985),
107(4), 1144-1155.
Abstract:
Dietary nitrate supplementation reduces the O2 cost of low-intensity exercise and enhances tolerance to high-intensity exercise in humans.
Pharmacological sodium nitrate supplementation has been reported to reduce the O2 cost of submaximal exercise in humans. In this study, we hypothesized that dietary supplementation with inorganic nitrate in the form of beetroot juice (BR) would reduce the O2 cost of submaximal exercise and enhance the tolerance to high-intensity exercise. In a double-blind, placebo (PL)-controlled, crossover study, eight men (aged 19-38 yr) consumed 500 ml/day of either BR (containing 11.2 +/- 0.6 mM of nitrate) or blackcurrant cordial (as a PL, with negligible nitrate content) for 6 consecutive days and completed a series of "step" moderate-intensity and severe-intensity exercise tests on the last 3 days. On days 4-6, plasma nitrite concentration was significantly greater following dietary nitrate supplementation compared with PL (BR: 273 +/- 44 vs. PL: 140 +/- 50 nM; P < 0.05), and systolic blood pressure was significantly reduced (BR: 124 +/- 2 vs. PL: 132 +/- 5 mmHg; P < 0.01). During moderate exercise, nitrate supplementation reduced muscle fractional O2 extraction (as estimated using near-infrared spectroscopy). The gain of the increase in pulmonary O2 uptake following the onset of moderate exercise was reduced by 19% in the BR condition (BR: 8.6 +/- 0.7 vs. PL: 10.8 +/- 1.6 ml.min(-1).W(-1); P < 0.05). During severe exercise, the O2 uptake slow component was reduced (BR: 0.57 +/- 0.20 vs. PL: 0.74 +/- 0.24 l/min; P < 0.05), and the time-to-exhaustion was extended (BR: 675 +/- 203 vs. PL: 583 +/- 145 s; P < 0.05). The reduced O2 cost of exercise following increased dietary nitrate intake has important implications for our understanding of the factors that regulate mitochondrial respiration and muscle contractile energetics in humans.
Abstract.
Author URL.
Ingham SA, Fudge BW, Pringle JS, Jones AM (2009). Effect of Prior Warm-up on Oxygen Uptake Kinetics During an 800-m Performance Trial. Medicine & Science in Sports & Exercise, 41(5).
Palmer CD, Jones AM, Kennedy GJ, Cotter JD (2009). Effects of Prior Heavy Exercise on Energy Supply and 4000-m Cycling Performance.
MED SCI SPORT EXER,
41(1), 221-229.
Abstract:
Effects of Prior Heavy Exercise on Energy Supply and 4000-m Cycling Performance
PALMER, C. D. A.M. JONES, G. J. KENNEDY, and J. D. COTTER. Effects of Prior Heavy Exercise on Energy Supply and 4000-m Cycling Performance. Med. Sci. Sports Exerc. Vol. 41, No. 1, pp. 221-229, 2009. Purpose: This study was designed to determine the effects of prior exercise on energy supply and performance in a laboratory-based 4000-m time trial. Methods: After one familiarization trial, eight well-trained cyclists (mean +/- SD; age 30 +/- 8 yr, body mass = 78.7 +/- 8.6 kg, stature = 181 +/- 5 cm, (V) over dot O-2 (peak) = 63.7 +/- 6.7 mL.kg(-1).min(-1), peak power output (PPO) = 366 +/- 39 W) performed three 4000-m laboratory-based cycling time trials each preceded by one of three prior exercise regimens in randomized order: no prior exercise (control), prior heavy exercise, and self-selected prior exercise. Results: Cyclists adopted a wide range of self-selected prior exercise regimens: duration ranged 11-80 min, intensity = 48-120% PPO, and recovery = 2-11 min. Relative to control, pre-time-trial blood lactate was raised by 2.5 +/- 1.9 and 1.4 +/- 1.5 mmol.L-1 after prior heavy and self-selected exercise, respectively. The 4000 m was completed 2.0 +/- 2.3% and 2.2 +/- 1.9% faster after prior heavy and self-selected exercise regimens, respectively, and mean power output was 5.4 +/- 3.6% and 6.0 +/- 5.8% higher, respectively. The overall aerobic contribution ((V) over dot O-2) and oxygen deficit were not different between conditions (similar to 323 +/- 23 and similar to 64 +/- 22 mL.kg(-1), respectively), although (V) over dot O-2 was higher (P < 0.05) in the prior heavy (by 2.1-5.8 mL.kg(-1).min(-1)) and self-selected (2.5-4.3 mL.kg(-1).min(-1)) regimens compared with the control throughout the first half of the time trial. Conclusion: Very high intensity cycling performance was improved after both self-selected and prior heavy exercise. Such priming increased the early aerobic contribution but did not change overall aerobic contribution or oxygen deficit. Thus, athletes seem to manage their energy potential to exploit the available anaerobic capacity, independent of the aerobic contribution. Athletes are advised to perform a bout of heavy exercise as part of their prior exercise regimen.
Abstract.
Vanhatalo A, Jones AM (2009). Influence of Creatine Supplementation on the Parameters of the All-out Critical Power Test. Medicine & Science in Sports & Exercise, 41(5).
Vanhatalo A, Jones AM (2009). Influence of creatine supplementation on the parameters of the "All-out critical power test".
Journal of Exercise Science and Fitness,
7(1), 9-17.
Abstract:
Influence of creatine supplementation on the parameters of the "All-out critical power test"
We tested the hypotheses that creatine loading would result in no alteration in critical power (CP) or the total work done >CP (W') as estimated from a novel 3-minute all-out cycling protocol. Seven habitually active male subjects completed 3-minute all-out tests against fixed resistance on an electrically-braked cycle ergometer after a 5-day dietary supplementation with 20 g · d-1 of a glucose placebo (PL) and the same dose of creatine monohydrate (CR). The CP was estimated from the mean power output over the final 30 seconds of the test and the W' was estimated as the power-time integral above the end-test power output. Creatine supplementation resulted in a significant increase in body mass (from 80.4 ± 9.2 kg to 81.5 ± 9.5 kg; p0.05). There were no differences in the power outputs measured during the 3-minute all-out tests following PL and CR supplementation (CP-PL: 252±30W vs. CR: 255 ± 28 W, p>0.05; W'-PL: 19.4±3.5kJ vs. CR: 19.2 ± 3.4 kJ, p>0.05; total work done-PL: 64.8 ± 4.9 kJ vs. CR: 65.0 ± 4.9 kJ, p> 0.05). Creatine loading had no ergogenic effect on the CP measured using the novel all-out protocol. In contrast to earlier studies which established the power-duration relationship using the conventional protocol, the finite work capacity > CP (W') for all-out exercise was not enhanced by creatine loading. [J Exerc Sci Fit • Vol 7 • No 1 • 9-17 • 2009].
Abstract.
Vanhatalo A, Jones AM (2009). Influence of creatine supplementation on the parameters of the "all-out critical power test".
J EXERC SCI FIT,
7(1), 9-17.
Abstract:
Influence of creatine supplementation on the parameters of the "all-out critical power test"
We tested the hypotheses that creatine loading would result in no alteration in critical power (CP) or the total work done > CP (W') as estimated from a novel 3-minute all-out cycling protocol. Seven habitually active male subjects completed 3-minute all-out tests against fixed resistance on an electrically-braked cycle ergometer after a 5-day dietary supplementation with 20 g. d(-1) of a glucose placebo (PL) and the same dose of creatine monohydrate (CR). The CP was estimated from the mean power output over the final 30 seconds of the test and the W' was estimated as the power-time integral above the end-test power output. Creatine supplementation resulted in a significant increase in body mass (from 80.4 +/- 9.2 kg to 81.5 +/- 9.5 kg; p < 0.05), whereas the body mass was not different after placebo supplementation (80.3 +/- 9.3 kg; p > 0.05). There were no differences in the power outputs measured during the 3-minute all-out tests Following PL and CR supplementation (CP-PL: 252 +/- 30 W vs. CR: 255 +/- 28 W p > 0.05; W'-PL: 19.4 +/- 3.5 kJ vs. CR: 19.2 +/- 3.4 kJ, p > 0.05; total work done-PL: 64.8 +/- 4.9 kJ vs. CR: 65.0 +/- 4.9 kJ, p > 0.05). Creatine loading had no ergogenic effect on the CP measured using the novel all-out protocol. in contrast to earlier studies which established the power-duration relationship using the conventional protocol, the finite work capacity > CP (W') for all-out exercise was not enhanced by creatine loading. [J Exerc Sci Fit. Vol 7. No 1. 9-17. 2009]
Abstract.
Wilkerson DP, Campbell IT, Blackwell JR, Berger NJ, Jones AM (2009). Influence of dichloroacetate on pulmonary gas exchange and ventilation during incremental exercise in healthy humans.
Respir Physiol Neurobiol,
168(3), 224-229.
Abstract:
Influence of dichloroacetate on pulmonary gas exchange and ventilation during incremental exercise in healthy humans.
We hypothesised that dichloroacetate (DCA) would reduce blood lactate accumulation, pulmonary carbon dioxide output (.V(CO2)) and ventilation (.V(E)) at sub-maximal work rates, and improve exercise tolerance during incremental exercise in healthy humans. Nine males (mean+/-SD, age 27+/-4 years) completed, in random order, two ramp incremental cycle ergometer tests to the limit of tolerance following the intravenous infusion of DCA (75 mg/kg body mass in 80 ml saline) or an equivalent volume of saline (as placebo). Relative to control, blood [lactate] was significantly reduced by DCA immediately before exercise (CON: 0.7+/-0.2 vs. DCA: 0.5+/-0.2mM; P
Abstract.
Author URL.
Wilkerson DP, Campbell IT, Blackwell JR, Jones AM (2009). Influence of dichloroacetate on pulmonary gas exchange during incremental cycle exercise in healthy humans. Respir Physiol Neurobiol
Jones AM, Wilkerson DP, Fulford J (2009). Influence of dietary creatine supplementation on muscle phosphocreatine kinetics during knee-extensor exercise in humans.
Am J Physiol Regul Integr Comp Physiol,
296(4), R1078-R1087.
Abstract:
Influence of dietary creatine supplementation on muscle phosphocreatine kinetics during knee-extensor exercise in humans.
We hypothesized that increasing skeletal muscle total creatine (Cr) content through dietary Cr supplementation would result in slower muscle phosphocreatine concentration ([PCr]) kinetics, as assessed using (31)P magnetic resonance spectroscopy, following the onset and offset of both moderate-intensity (Mod) and heavy-intensity (Hvy) exercise. Seven healthy males (age 29 +/- 6 yr, mean +/- SD) completed a series of square-wave transitions to Mod and Hvy knee extensor exercise inside the bore of a 1.5-T superconducting magnet both before and after a 5-day period of Cr loading (4x 5 g/day of creatine monohydrate). Cr supplementation resulted in an approximately 8% increase in the resting muscle [PCr]-to-[ATP] ratio (4.66 +/- 0.27 vs. 5.04 +/- 0.22; P < 0.05), consistent with a significant increase in muscle total Cr content consequent to the intervention. The time constant for muscle [PCr] kinetics was increased following Cr loading for Mod exercise (control: 15 +/- 8 vs. Cr: 25 +/- 9 s; P < 0.05) and subsequent recovery (control: 14 +/- 8 vs. Cr: 27 +/- 8 s; P < 0.05) and for Hvy exercise (control: 54 +/- 18 vs. Cr: 72 +/- 30 s; P < 0.05), but not for subsequent recovery (control: 41 +/- 11 vs. Cr: 44 +/- 6 s). The magnitude of the increase in [PCr] following Cr loading was correlated (P < 0.05) with the extent of the slowing of the [PCr] kinetics for the moderate off-transient (r = 0.92) and the heavy on-transient (r = 0.71). These data demonstrate, for the first time in humans, that an increase in muscle [PCr] results in a slowing of [PCr] dynamics in exercise and subsequent recovery.
Abstract.
Author URL.
DiMenna FJ, Wilkerson DP, Burnley M, Bailey SJ, Jones AM (2009). Influence of extreme pedal rates on pulmonary O-2 uptake kinetics during transitions to high-intensity exercise from an elevated baseline.
RESPIRATORY PHYSIOLOGY & NEUROBIOLOGY,
169(1), 16-23.
Author URL.
DiMenna FJ, Wilkerson DP, Burnley M, Bailey SJ, Jones AM (2009). Influence of extreme pedal rates on pulmonary O<inf>2</inf> uptake kinetics during transitions to high-intensity exercise from an elevated baseline.
Respiratory Physiology and Neurobiology,
169(1), 16-23.
Abstract:
Influence of extreme pedal rates on pulmonary O2 uptake kinetics during transitions to high-intensity exercise from an elevated baseline
We used extreme pedal rates to investigate the influence of muscle fibre recruitment on pulmonary over(V, ̇)O2 kinetics during unloaded-to-moderate-intensity (U → M), unloaded-to-high-intensity (U → H), and moderate-intensity to high-intensity (M → H) cycling transitions. Seven healthy men completed transitions to 60% of the difference between gas-exchange threshold and peak over(V, ̇)O2 from both an unloaded and a moderate-intensity (95% GET) baseline at cadences of 35 and 115 rpm. Pulmonary gas exchange was measured breath-by-breath and iEMG of the m. vastus lateralis and m. gluteus maximus was measured during all tests. At 35 rpm, the phase II time constant (τp) values for U → M, U → H, and M → H were 26 ± 7, 31 ± 7 and 36 ± 8 s with the value for M → H being longer than for U → M (P < 0.05). At 115 rpm, the τp values for U → M, U → H, and M → H were 29 ± 8, 48 ± 16 and 53 ± 20 s with the value for U → M being shorter than for the other two conditions (P < 0.05). The over(V, ̇)O2 slow component was similar at both cadences, but iEMG only increased beyond minute 2 during high-intensity cycling at 115 rpm. These results demonstrate that over(V, ̇)O2 kinetics are influenced by an interaction of exercise intensity and pedal rate and are consistent with the notion that changes in muscle fibre recruitment are responsible for slower phase II over(V, ̇)O2 kinetics during high-intensity and work-to-work exercise transitions. © 2009 Elsevier B.V. All rights reserved.
Abstract.
Mauger AR, Jones AM, Williams CA (2009). Influence of feedback and prior experience on pacing during a 4-km cycle time trial.
Med Sci Sports Exerc,
41(2), 451-458.
Abstract:
Influence of feedback and prior experience on pacing during a 4-km cycle time trial.
PURPOSE: to determine the importance of distance knowledge, distance feedback, and prior experience on the setting of a pacing strategy. METHODS: Eighteen well-trained male cyclists were randomly assigned to a control (CON) group or an experimental (EXP) group and performed four consecutive 4-km time trials (TT), separated by a 17-min recovery. The CON group received prior knowledge of distance to be cycled and received distance feedback throughout each TT; the EXP group received neither but knew that each TT was of the same distance. RESULTS: the EXP group was significantly slower than the CON group to complete TT1 (367.4 +/- 21 vs 409.4 +/- 45.5 s, P < 0.001). Differences between groups in completion time reduced over successive TT (CON TT4 = 373.9 +/- 20 s vs EXP TT4 = 373.8 +/- 14.4 s), shown by a significant linear contrast (F1,16 = 12.39, P < 0.0005). Mean speed and power output also showed significantly reduced differences between groups over successive TT (P < 0.0005). However, peak power output showed no such convergence between groups over TT. End blood lactate was significantly different between groups in TT1, but differences between groups converged with successive TT. CONCLUSION: the progressively improving completion times in the EXP group show that distance feedback is not essential in developing an appropriate pacing strategy. Prior experience of an unknown distance appears to allow the creation of an internal, relative distance that is used to establish a pacing strategy.
Abstract.
Author URL.
DiMenna FJ, Wilkerson DP, Burnley M, Bailey SJ, Jones AM (2009). Influence of priming exercise on pulmonary O2 uptake kinetics during transitions to high-intensity exercise at extreme pedal rates.
J Appl Physiol (1985),
106(2), 432-442.
Abstract:
Influence of priming exercise on pulmonary O2 uptake kinetics during transitions to high-intensity exercise at extreme pedal rates.
We investigated the pedal rate dependency of the effect of priming exercise on pulmonary oxygen uptake (Vo(2)) kinetics. Seven healthy men completed two, 6-min bouts of high-intensity cycle exercise (separated by 6 min of rest) using different combinations of extreme pedal rates for the priming and criterion exercise bouts (i.e. 35-->35, 35-->115, 115-->35, and 115-->115 rev/min). Pulmonary gas exchange and heart rate were measured breath-by-breath, and muscle oxygenation was assessed using near-infrared spectroscopy. When the priming bout was performed at 35 rev/min (35-->35 and 35-->115 conditions), the phase II Vo(2) time constant (tau) was not significantly altered (bout 1: 31 +/- 7 vs. bout 2: 30 +/- 5 s and bout 1: 48 +/- 16 vs. bout 2: 46 +/- 21 s, respectively). However, when the priming bout was performed at 115 rev/min (115-->35 and 115-->115 conditions), the phase II tau was significantly reduced (bout 1: 31 +/- 7 vs. bout 2: 26 +/- 5 s and bout 1: 48 +/- 16 vs. bout 2: 39 +/- 9 s, respectively, P < 0.05). Muscle oxygenation was significantly higher after priming exercise in all four conditions, but significant effects on Vo(2) kinetics were only evident when muscle O(2) extraction (measured as Delta[deoxyhemoglobin]/DeltaVo(2)) was elevated in the fundamental response phase. These data indicate that prior high-intensity exercise at a high pedal rate can speed Vo(2) kinetics during subsequent high-intensity exercise, presumably through specific priming effects on type II muscle fibers.
Abstract.
Author URL.
Vanhatalo A, Jones AM (2009). Influence of prior sprint exercise on the parameters of the 'all-out critical power test' in men.
Exp Physiol,
94(2), 255-263.
Abstract:
Influence of prior sprint exercise on the parameters of the 'all-out critical power test' in men.
We tested the hypothesis that a prior 30 s sprint exercise bout would significantly reduce the curvature constant (W') but not the power-asymptote (critical power, CP) of the power-duration relationship as assessed using a novel 3 min all-out cycling test. Seven physically active male subjects completed the 3 min all-out test on three occasions in random order: following no prior sprint exercise (control, C); following a 30 s sprint and a 2 min recovery (S2); and following a 30 s sprint and a 15 min recovery period (S15). The CP was estimated from the mean power output sustained over the final 30 s of the test and the W' was estimated as the power-time integral above the end-test power. There were no significant differences in the estimated CP between the control 3 min all-out trial and the two prior sprint conditions (C, 235 +/- 44 W; S2, 223 +/- 46 W; and S15, 232 +/- 50 W; P > 0.05; coefficients of variation 2, 3 and 6% for C-S2, C-S15 and S2-S15, respectively). However, the W' in S2 (16.5 +/- 3.3 kJ) was significantly lower than in C (20.8 +/- 3.9 kJ) and S15 (21.2 +/- 4.5 kJ; P < 0.05). The total work done was lower in S2 than in the other conditions (S2, 56.4 +/- 7.2 kJ; C, 63.5 +/- 6.6 kJ; and S15, 63.0 +/- 6.0 kJ; P < 0.05). The W', but not the CP, is sensitive to a bout of prior sprint exercise which would be expected to result in significant muscle phosphocreatine depletion. These findings support the fundamental principles of the power-duration relationship as applied to all-out exercise.
Abstract.
Author URL.
Bailey SJ, Wilkerson DP, Dimenna FJ, Jones AM (2009). Influence of repeated sprint training on pulmonary O2 uptake and muscle deoxygenation kinetics in humans.
J Appl Physiol (1985),
106(6), 1875-1887.
Abstract:
Influence of repeated sprint training on pulmonary O2 uptake and muscle deoxygenation kinetics in humans.
We hypothesized that a short-term training program involving repeated all-out sprint training (RST) would be more effective than work-matched, low-intensity endurance training (ET) in enhancing the kinetics of oxygen uptake (Vo(2)) and muscle deoxygenation {deoxyhemoglobin concentration ([HHb])} following the onset of exercise. Twenty-four recreationally active subjects (15 men, mean +/- SD: age 21 +/- 4 yr, height 173 +/- 9 cm, body mass 71 +/- 11 kg) were allocated to one of three groups: RST, which completed six sessions of four to seven 30-s RSTs; ET, which completed six sessions of work-matched, moderate-intensity cycling; and a control group (CON). All subjects completed moderate-intensity and severe-intensity "step" exercise transitions before (Pre) and after the 2-wk intervention period (Post). Following RST, [HHb] kinetics were speeded, and the amplitude of the [HHb] response was increased during both moderate and severe exercise (P < 0.05); the phase II Vo(2) kinetics were accelerated for both moderate (Pre: 28 +/- 8, Post: 21 +/- 8 s; P < 0.01) and severe (Pre: 29 +/- 5, Post: 23 +/- 5 s; P < 0.05) exercise; the amplitude of the Vo(2) slow component was reduced (Pre: 0.52 +/- 0.19, Post: 0.40 +/- 0.17 l/min; P < 0.01); and exercise tolerance during severe exercise was improved by 53% (Pre: 700 +/- 234, Post: 1,074 +/- 431 s; P < 0.01). None of these parameters was significantly altered in the ET and CON groups. Six sessions of RST, but not ET, resulted in changes in [HHb] kinetics consistent with enhanced fractional muscle O(2) extraction, faster Vo(2) kinetics, and an increased tolerance to high-intensity exercise.
Abstract.
Author URL.
Jones AM, Krustrup P, Wilkerson DP, Calbet J, Bangsbo J (2009). Muscle and Pulmonary Oxygen Uptake Kinetics During Moderate and High-intensity Knee-extensor Exercise in Humans. Medicine & Science in Sports & Exercise, 41(5), 117-118.
Krustrup P, Jones AM, Wilkerson DP, Calbet JA, Bangsbo J (2009). Muscular and pulmonary O2 uptake kinetics during moderate and high-intensity sub-maximal knee-extensor exercise in humans. J Physiol, 587, 1843-1856.
Krustrup P, Jones AM, Wilkerson DP, Calbet JAL, Bangsbo J (2009). Muscular and pulmonary O2 uptake kinetics during moderate- and high-intensity sub-maximal knee-extensor exercise in humans.
J Physiol,
587(Pt 8), 1843-1856.
Abstract:
Muscular and pulmonary O2 uptake kinetics during moderate- and high-intensity sub-maximal knee-extensor exercise in humans.
The purpose of this investigation was to determine the contribution of muscle O(2) consumption (mVO2) to pulmonary O(2) uptake (pVO2) during both low-intensity (LI) and high-intensity (HI) knee-extension exercise, and during subsequent recovery, in humans. Seven healthy male subjects (age 20-25 years) completed a series of LI and HI square-wave exercise tests in which mVO2 (direct Fick technique) and pVO2 (indirect calorimetry) were measured simultaneously. The mean blood transit time from the muscle capillaries to the lung (MTTc-l) was also estimated (based on measured blood transit times from femoral artery to vein and vein to artery). The kinetics of mVO2 and pVO2 were modelled using non-linear regression. The time constant (tau) describing the phase II pVO2 kinetics following the onset of exercise was not significantly different from the mean response time (initial time delay + tau) for mVO2 kinetics for LI (30 +/- 3 vs 30 +/- 3 s) but was slightly higher (P < 0.05) for HI (32 +/- 3 vs 29 +/- 4 s); the responses were closely correlated (r = 0.95 and r = 0.95; P < 0.01) for both intensities. In recovery, agreement between the responses was more limited both for LI (36 +/- 4 vs 18 +/- 4 s, P < 0.05; r = -0.01) and HI (33 +/- 3 vs 27 +/- 3 s, P > 0.05; r = -0.40). MTTc-l was approximately 17 s just before exercise and decreased to 12 and 10 s after 5 s of exercise for LI and HI, respectively. These data indicate that the phase II pVO2 kinetics reflect mVO2 kinetics during exercise but not during recovery where caution in data interpretation is advised. Increased mVO2 probably makes a small contribution to during the first 15-20 s of exercise.
Abstract.
Author URL.
Bailey SJ, Vanhatalo A, Wilkerson DP, Dimenna FJ, Jones AM (2009). Optimizing the "priming" effect: influence of prior exercise intensity and recovery duration on O2 uptake kinetics and severe-intensity exercise tolerance.
J Appl Physiol (1985),
107(6), 1743-1756.
Abstract:
Optimizing the "priming" effect: influence of prior exercise intensity and recovery duration on O2 uptake kinetics and severe-intensity exercise tolerance.
It has been suggested that a prior bout of high-intensity exercise has the potential to enhance performance during subsequent high-intensity exercise by accelerating the O(2) uptake (Vo(2)) on-response. However, the optimal combination of prior exercise intensity and subsequent recovery duration required to elicit this effect is presently unclear. Eight male participants, aged 18-24 yr, completed step cycle ergometer exercise tests to 80% of the difference between the preestablished gas exchange threshold and maximal Vo(2) (i.e. 80%Delta) after no prior exercise (control) and after six different combinations of prior exercise intensity and recovery duration: 40%Delta with 3 min (40-3-80), 9 min (40-9-80), and 20 min (40-20-80) of recovery and 70%Delta with 3 min (70-3-80), 9 min (70-9-80), and 20 min (70-20-80) of recovery. Overall Vo(2) kinetics were accelerated relative to control in all conditions except for 40-9-80 and 40-20-80 conditions as a consequence of a reduction in the Vo(2) slow component amplitude; the phase II time constant was not significantly altered with any prior exercise/recovery combination. Exercise tolerance at 80%Delta was improved by 15% and 30% above control in the 70-9-80 and 70-20-80 conditions, respectively, but was impaired by 16% in the 70-3-80 condition. Prior exercise at 40%Delta did not significantly influence exercise tolerance regardless of the recovery duration. These data demonstrate that prior high-intensity exercise ( approximately 70%Delta) can enhance the tolerance to subsequent high-intensity exercise provided that it is coupled with adequate recovery duration (>or=9 min). This combination presumably optimizes the balance between preserving the effects of prior exercise on Vo(2) kinetics and providing sufficient time for muscle homeostasis (e.g. muscle phosphocreatine and H(+) concentrations) to be restored.
Abstract.
Author URL.
Jones AM, Burnley M (2009). Oxygen uptake kinetics: an underappreciated determinant of exercise performance.
Int J Sports Physiol Perform,
4(4), 524-532.
Abstract:
Oxygen uptake kinetics: an underappreciated determinant of exercise performance.
The rate at which VO(2) adjusts to the new energy demand following the onset of exercise strongly influences the magnitude of the "O(2) deficit" incurred and thus the extent to which muscle and systemic homeostasis is perturbed. Moreover, during continuous high-intensity exercise, there is a progressive loss of muscle contractile efficiency, which is reflected in a "slow component" increase in VO(2). The factors that dictate the characteristics of these fast and slow phases of the dynamic response of VO(2) following a step change in energy turnover remain obscure. However, it is clear that these features of the VO(2) kinetics have the potential to influence the rate of muscle fatigue development and, therefore, to affect sports performance. This commentary outlines the present state of knowledge on the characteristics of, and mechanistic bases to, the VO(2) response to exercise of different intensities. Several interventions have been reported to speed the early VO(2) kinetics and/or reduce the magnitude of the subsequent VO(2) slow component, and the possibility that these might enhance exercise performance is discussed.
Abstract.
Author URL.
Tolfrey K, Hansen SA, Dutton K, McKee T, Jones AM (2009). Physiological correlates of 2-mile run performance as determined using a novel on-demand treadmill.
Appl Physiol Nutr Metab,
34(4), 763-772.
Abstract:
Physiological correlates of 2-mile run performance as determined using a novel on-demand treadmill.
The purpose of this study was to assess the reproducibility of an on-demand motorised treadmill to measure 2-mile (3.2 km) race performance and to examine the physiological variables that best predict this free-running performance in active men. Twelve men (mean (SD): age, 28 (9) years; stature, 1.79 (0.05) m; body mass, 72 (9) kg) completed the study in which maximum oxygen uptake (VO2 max), running economy, and running speedin the abstract section. They appear in the rest of the paper.), running economy, and running speed at VO2 max (vVO2 max), lactate threshold (vLT), and 4 mmol.L-1 fixed blood lactate concentration (v4) were measured. Subsequently, the maximal lactate steady state (MLSS) was identified using a series of 30-min treadmill runs. Finally, each participant completed a 2-mile running performance trial on 2 separate occasions, using an on-demand treadmill that adjusts belt speed according to the participant's position on the moving belt. The average 2-mile run speed was 15.7 (SD, 1.9) km.h-1, with small individual differences between repeat-performance trials (intraclass correlation coefficient = 0.99, 95% CI 0.953 to 0.996; standard error of measurement as coefficient of variation = 1.5%, 95% CI 1.0% to 2.5%). Bivariate regression analyses identified VO2 max, vVO2 max, VO2 (mL.kg-1.min-1) at MLSS, vLT, v4, and velocity at MLSS (vMLSS) as the strongest individual predictor variables (r2 = 0.69 to 0.87; standard error of the estimate = 1.08 to 0.72 km.h-1) for 2-mile running performance. The vLT and vMLSS explained 85% and 87% of the variance in running performance, respectively, suggesting that there is considerable shared variance between these parameters. In conclusion, the on-demand treadmill system provided a reliable measure of distance running performance. Both vLT and vMLSS were strong predictors of 2-mile running performance, with vMLSS explaining marginally more of the variance.
Abstract.
Author URL.
Davison RCR, Van Someren KA, Jones AM (2009). Physiological monitoring of the Olympic athlete.
JOURNAL OF SPORTS SCIENCES,
27(13), 1433-1442.
Author URL.
Benjamin N, Bailey SJ, Vanhatalo A, Winyard P, Jones AM (2009). Reply to Derave and Taes. Journal of Applied Physiology, 107(5).
Jones AM, Davies RC, Ferreira LF, Barstow TJ, Koga S, Poole DC (2009). Reply to quaresima and ferrari. J Appl Physiol, 107(1), 372-373.
Jones AM, DiMenna F, Lothian F, Taylor E, Garland SW, Hayes PR, Thompson KG (2008). 'Priming' exercise and O2 uptake kinetics during treadmill running.
Respir Physiol Neurobiol,
161(2), 182-188.
Abstract:
'Priming' exercise and O2 uptake kinetics during treadmill running.
We tested the hypothesis that priming exercise would speed V(O2) kinetics during treadmill running. Eight subjects completed a square-wave protocol, involving two bouts of treadmill running at 70% of the difference between the running speeds at lactate threshold (LT) and V(O2) max, separated by 6-min of walking at 4 km h(-1), on two occasions. Oxygen uptake was measured breath-by-breath and subsequently modelled using non-linear regression techniques. Heart rate and blood lactate concentration were significantly elevated prior to the second exercise bout compared to the first. However, V(O2) kinetics was not significantly different between the first and second exercise bouts (mean+/-S.D. phase II time constant, Bout 1: 16+/-3s vs. Bout 2: 16+/-4s; V(O2) slow component amplitude, Bout 1: 0.24+/-0.10 L min(-1)vs. Bout 2: 0.20+/-0.12 L min(-1); mean response time, Bout 1: 34+/-4s vs. Bout 2: 34+/-6s; P>0.05 for all comparisons). These results indicate that, contrary to previous findings with other exercise modalities, priming exercise does not alter V(O2) kinetics during high-intensity treadmill running, at least in physically active young subjects. We speculate that the relatively fast V(O2) kinetics and the relatively small V(O2) slow component in the control ('un-primed') condition negated any enhancement of V(O2) kinetics by priming exercise in this exercise modality.
Abstract.
Author URL.
Jones AM (2008). Capillary blood volume increase in already perfused capillaries: Role for glycocalyx modulation. J APPL PHYSIOL, 104(3), 895-896.
Burnley M, Jones AM (2008). Commentaries on Viewpoint: Fatigue mechanisms determining exercise performance: Integrative physiology is systems physiology. J APPL PHYSIOL, 104(5), 1545-1546.
Poole DC, Barstow TJ, McDonough P, Jones AM (2008). Control of oxygen uptake during exercise.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
40(3), 462-474.
Abstract:
Control of oxygen uptake during exercise
Other than during sleep and contrived laboratory testing protocols, humans rarely exist in prolonged metabolic steady states; rather, they transition among different metabolic rates (VO2). The dynamic transition of VO2 (VO2 kinetics), initiated, for example, at exercise onset, provides a unique window into understanding metabolic control. This brief review presents the state-of-the art regarding control of VO2 kinetics within the context of a simple model that helps explain the work rate dependence of VO2 kinetics as well as the effects of environmental perturbations and disease. Insights emerging from application of novel approaches and technologies are integrated into established concepts to assess in what circumstances O-2 supply might exert a commanding role over VO2 kinetics, and where it probably does not. The common presumption that capillary blood flow dynamics can be extrapolated accurately from upstream arterial measurements is challenged. From this challenge, new complexities emerge with respect to the relationships between O-2 Supply and flux across the capillary-myocyte interface and the marked dependence of these processes on muscle fiber type. Indeed, because of interfiber type differences in O-2 supply relative to VO2, the presence of much lower O-2 levels in the microcirculation supplying fast-twitch muscle fibers, and the demonstrated metabolic sensitivity of muscle to O-2, it is possible that fiber type recruitment profiles (and changes thereof) might help explain the slowing of VO2 kinetics at higher work rates and in chronic diseases such as heart failure and diabetes.
Abstract.
Davies RC, Eston RG, Poole DC, Rowlands AV, DiMenna F, Wilkerson DP, Twist C, Jones AM (2008). Effect of eccentric exercise-induced muscle damage on the dynamics of muscle oxygenation and pulmonary oxygen uptake.
J Appl Physiol (1985),
105(5), 1413-1421.
Abstract:
Effect of eccentric exercise-induced muscle damage on the dynamics of muscle oxygenation and pulmonary oxygen uptake.
Unaccustomed eccentric exercise has a profound impact on muscle structure and function. However, it is not known whether associated microvascular dysfunction disrupts the matching of O2 delivery (Qo2) to O2 utilization (Vo2). Near-infrared spectroscopy (NIRS) was used to test the hypothesis that eccentric exercise-induced muscle damage would elevate the muscle Qo2:Vo2 ratio during severe-intensity exercise while preserving the speed of the Vo2 kinetics at exercise onset. Nine physically active men completed "step" tests to severe-intensity exercise from an unloaded baseline on a cycle ergometer before (Pre) and 48 h after (Post) eccentric exercise (100 squats with a load corresponding to 70% of body mass). NIRS and breath-by-breath pulmonary Vo2 were measured continuously during the exercise tests and subsequently modeled using standard nonlinear regression techniques. There were no changes in phase II pulmonary Vo2 kinetics following the onset of exercise (time constant: Pre, 25 +/- 4 s; Post, 24 +/- 2 s; amplitude: Pre, 2.36 +/- 0.23 l/min; Post, 2.37 +/- 0.23 l/min; all P > 0.05). However, the primary (Pre, 14 +/- 3 s; Post, 19 +/- 3 s) and overall (Pre, 16 +/- 4 s; Post, 21 +/- 4 s) mean response time of the [HHb] response was significantly slower following eccentric exercise (P < 0.05). The slower [HHb] kinetics observed following eccentric exercise is consistent with an increased Qo2:Vo2 ratio during transitions to severe-intensity exercise. We propose that unchanged primary phase Vo2 kinetics are associated with an elevated Qo2:Vo2 ratio that preserves blood-myocyte O2 flux.
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Author URL.
Gerstein HC, Miller ME, Byington RP, Goff DC, Bigger JT, Buse JB, Cushman WC, Genuth S, Ismail-Beigi F, Grimm RH, et al (2008). Effects of intensive glucose lowering in type 2 diabetes.
New England Journal of Medicine,
358(24), 2545-2559.
Abstract:
Effects of intensive glucose lowering in type 2 diabetes
Background Epidemiologic studies have shown a relationship between glycated hemoglobin levels and cardiovascular events in patients with type 2 diabetes. We investigated whether intensive therapy to target normal glycated hemoglobin levels would reduce cardiovascular events in patients with type 2 diabetes who had either established cardiovascular disease or additional cardiovascular risk factors. Methods in this randomized study, 10,250 patients (mean age, 60.2 years) with a median glycated hemoglobin level of 8.1% were assigned to receive intensive therapy (targeting a glycated hemoglobin level below 6.0%) or standard therapy (targeting a level from 7.0 to 7.9%). of these patients, 37% were women, and 7% had had a previous cardiovascular event. The primary outcome was a composite of nonfatal myocardial infarction, nonfatal stroke, or death from cardiovascular causes. The finding of higher mortality in the intensive-therapy group led to a discontinuation of intensive therapy after a mean of 3.5 years of follow-up. Results at 1 year, stable median glycated hemoglobin levels of 6.4% and 7.5% were achieved in the intensive-therapy group and the standard-therapy group, respectively. During follow-up, the primary outcome occurred in 70 patients in the intensive-therapy group, as compared with 359 in the standard-therapy group (hazard ratio, 0.88; 92% confidence interval [CI], 0.76 to 1.04; P = 0.16). At the same time, 255 patients in the intensive-therapy group died, as compared with 203 patients in the standardtherapy group (hazard ratio, 1.22; 92% CI, 1.01 to 1.45; P = 0.04). Hypoglycemia requiring assistance and weight gain of more than 10 kg were more frequent in the intensive-therapy group (P
Abstract.
Jones AM (2008). In response to "Point:Counterpoint: There is/is not capillary recruitment in active skeletal muscle during exercise".
J Appl Physiol (1985),
104(3), 895-896.
Author URL.
Jones AM, Wilkerson DP, Vanhatalo A, Burnley M (2008). Influence of pacing strategy on O2 uptake and exercise tolerance.
Scand J Med Sci Sports,
18(5), 615-626.
Abstract:
Influence of pacing strategy on O2 uptake and exercise tolerance.
Seven male subjects completed cycle exercise bouts to the limit of tolerance on three occasions: (1) at a constant work rate (340+/-57 W; even-pace strategy; ES); (2) at a work rate that was initially 10% lower than that in the ES trial but which then increased with time such that it was 10% above that in the ES trial after 120 s of exercise (slow-start strategy; SS); and, (3) at a work rate that was initially 10% higher than that in the ES trial but which then decreased with time such that it was 10% below that in the ES trial after 120 s of exercise (fast-start strategy; FS). The expected time to exhaustion predicted from the pre-established power-time relationship was 120 s in all three conditions. However, the time to exhaustion was significantly greater (P
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DiMenna FJ, Wilkerson DP, Burnley M, Jones AM (2008). Influence of priming exercise on pulmonary O2 uptake kinetics during transitions to high-intensity exercise from an elevated baseline.
J Appl Physiol (1985),
105(2), 538-546.
Abstract:
Influence of priming exercise on pulmonary O2 uptake kinetics during transitions to high-intensity exercise from an elevated baseline.
It has been suggested that the slower O2 uptake (VO2) kinetics observed when exercise is initiated from an elevated baseline metabolic rate are linked to an impairment of muscle O2 delivery. We hypothesized that "priming" exercise would significantly reduce the phase II time constant (tau) during subsequent severe-intensity cycle exercise initiated from an elevated baseline metabolic rate. Seven healthy men completed exercise transitions to 70% of the difference between gas exchange threshold (GET) and peak VO2 from a moderate-intensity baseline (90% GET) on three occasions in each of the "unprimed" and "primed" conditions. Pulmonary gas exchange, heart rate, and the electromyogram of m. vastus lateralis were measured during all tests. The phase II VO2 kinetics were slower when severe exercise was initiated from a baseline of moderate exercise compared with unloaded pedaling (mean+/-SD tau, 42+/-15 vs. 33+/-8 s; P0.05). The amplitude of the VO2 slow component and the change in electromyogram from minutes 2 to 6 were both significantly reduced following priming exercise (VO2 slow component: from 0.47+/-0.09 to 0.27+/-0.13 l/min; change in integrated electromyogram between 2 and 6 min: from 51+/-35 to 26+/-43% of baseline; P
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Jones AM, Fulford J, Wilkerson DP (2008). Influence of prior exercise on muscle [phosphorylcreatine] and deoxygenation kinetics during high-intensity exercise in men.
Exp Physiol,
93(4), 468-478.
Abstract:
Influence of prior exercise on muscle [phosphorylcreatine] and deoxygenation kinetics during high-intensity exercise in men.
(31)Phosphate-magnetic resonance spectroscopy and near infrared spectroscopy (NIRS) were used for the simultaneous assessment of changes in quadriceps muscle metabolism and oxygenation during consecutive bouts of high-intensity exercise. Six male subjects completed two 6 min bouts of single-legged knee-extension exercise at 80% of the peak work rate separated by 6 min of rest while positioned inside the bore of a 1.5 T superconducting magnet. The total haemoglobin and oxyhaemoglobin concentrations in the area of the quadriceps muscle interrogated with NIRS were significantly higher in the baseline period prior to the second compared with the first exercise bout, consistent with an enhanced muscle oxygenation. Intramuscular phosphorylcreatine concentration ([PCr]) dynamics were not different over the fundamental region of the response (time constant for bout 1, 51 +/- 15 s versus bout 2, 52 +/- 17 s). However, the [PCr] dynamics over the entire response were faster in the second bout (mean response time for bout 1, 72 +/- 16 s versus bout 2, 57 +/- 8 s; P < 0.05), as a consequence of a greater fall in [PCr] in the fundamental phase and a reduction in the magnitude of the 'slow component' in [PCr] beyond 3 min of exercise (bout 1, 10 +/- 6% versus bout 2, 5 +/- 3%; P < 0.05). These data suggest that the increased muscle O(2) availability afforded by the performance of a prior bout of high-intensity exercise does not significantly alter the kinetics of [PCr] hydrolysis at the onset of a subsequent bout of high-intensity exercise. The greater fall in [PCr] over the fundamental phase of the response following prior high-intensity exercise indicates that residual fatigue acutely reduces muscle efficiency.
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Author URL.
Jones AM, Wilkerson DP, Fulford J (2008). Muscle [phosphocreatine] dynamics following the onset of exercise in humans: the influence of baseline work-rate.
J Physiol,
586(3), 889-898.
Abstract:
Muscle [phosphocreatine] dynamics following the onset of exercise in humans: the influence of baseline work-rate.
The kinetics of pulmonary O(2) uptake is known to be substantially slower when exercise is initiated from a baseline of lower-intensity exercise rather than from rest. However, it is not known whether putative intracellular regulators of mitochondrial respiration (and in particular the phosphocreatine concentration, [PCr]) show similar non-linearities in their response dynamics. The purpose of this study was therefore to investigate the influence of baseline metabolic rate on muscle [PCr] kinetics (as assessed using (31)P-magnetic resonance spectroscopy) following the onset of exercise. Seven male subjects completed 'step' tests to heavy-intensity exercise (80% of peak work-rate) from a resting baseline and also from a baseline of moderate-intensity exercise (40% of peak work-rate) using a single-leg knee-extensor ergometer situated inside the bore of a 1.5 T super-conducting magnet. The time constant describing the kinetics of the initial exponential-like fall in [PCr] was significantly different between rest-to-moderate (25 +/- 14 s), rest-to-heavy (48 +/- 11 s) and moderate-to-heavy exercise (95 +/- 40 s) (P < 0.05 for all comparisons). A delayed-onset 'slow component' in the [PCr] response was observed in all subjects during rest-to-heavy exercise, but was attenuated in the moderate-to-heavy exercise condition. These data indicate that muscle [PCr] kinetics does not conform to 'linear, first-order' behaviour during dynamic exercise, and thus have implications for understanding the regulation of muscle oxidative metabolism.
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Author URL.
Jones AM, Wilkerson DP, DiMenna F, Fulford J, Poole DC (2008). Muscle metabolic responses to exercise above and below the "critical power" assessed using 31P-MRS.
Am J Physiol Regul Integr Comp Physiol,
294(2), R585-R593.
Abstract:
Muscle metabolic responses to exercise above and below the "critical power" assessed using 31P-MRS.
We tested the hypothesis that the asymptote of the hyperbolic relationship between work rate and time to exhaustion during muscular exercise, the "critical power" (CP), represents the highest constant work rate that can be sustained without a progressive loss of homeostasis [as assessed using (31)P magnetic resonance spectroscopy (MRS) measurements of muscle metabolites]. Six healthy male subjects initially completed single-leg knee-extension exercise at three to four different constant work rates to the limit of tolerance (range 3-18 min) for estimation of the CP (mean +/- SD, 20 +/- 2 W). Subsequently, the subjects exercised at work rates 10% below CP (CP) for as long as possible, while the metabolic responses in the contracting quadriceps muscle, i.e. phosphorylcreatine concentration ([PCr]), P(i) concentration ([P(i)]), and pH, were estimated using (31)P-MRS. All subjects completed 20 min of CP exercise was 14.7 +/- 7.1 min. During CP exercise, however, [PCr] continued to fall to the point of exhaustion and [P(i)] and pH changed precipitously to values that are typically observed at the termination of high-intensity exhaustive exercise (end-exercise values = 26 +/- 16% of baseline [PCr], 564 +/- 167% of baseline [P(i)], and pH 6.87 +/- 0.10, all P < 0.05 vs.
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Author URL.
Poole DC, Wilkerson DP, Jones AM (2008). Validity of criteria for establishing maximal O2 uptake during ramp exercise tests.
Eur J Appl Physiol,
102(4), 403-410.
Abstract:
Validity of criteria for establishing maximal O2 uptake during ramp exercise tests.
The incremental or ramp exercise test to the limit of tolerance has become a popular test for determination of maximal O(2) uptake (VO(2max)). However, many subjects do not evidence a definitive plateau of the VO(2) -work rate relationship on this test and secondary criteria based upon respiratory exchange ratio (RER), maximal heart rate (HR(max)) or blood [lactate] have been adopted to provide confidence in the measured VO(2max). We hypothesized that verification of VO(2max) using these variables is fundamentally flawed in that their use could either allow underestimation of VO(2max) (if, for any reason, a test were ended at a sub-maximal [Formula: see text]), or alternatively preclude subjects from recording a valid VO(2max). Eight healthy male subjects completed a ramp exercise test (at 20 W/min) to the limit of tolerance on an electrically braked cycle ergometer during which pulmonary gas exchange was measured breath-by-breath and blood [lactate] was determined every 90 s. Using the most widely used criterion values of RER (1.10 and 1.15), VO(2max) as determined during the ramp test (4.03 +/- 0.10 l/min) could be undermeasured by 27% (2.97 +/- 0.24 l/min) and 16% (3.41 +/- 0.15 l/min), respectively (both P < 0.05). The criteria of HR(max) (age predicted HR(max) +/- 10 b/min) and blood [lactate] (> or = 8 mM) were untenable because they resulted in rejection of 3/8 and 6/8 of the subjects, most of whom (5/8) had demonstrated a plateau of VO(2max) at VO(2max). These findings provide a clear mandate for rejecting these secondary criteria as a means of validating VO(2max) on ramp exercise tests.
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Kilding AE, Jones AM (2008). Vo(2) 'overshoot' during moderate-intensity exercise in endurance-trained athletes: the influence of exercise modality.
RESP PHYSIOL NEUROBI,
160(2), 139-146.
Abstract:
Vo(2) 'overshoot' during moderate-intensity exercise in endurance-trained athletes: the influence of exercise modality
The purpose of this study was to investigate the influence of exercise modality on the 'overshoot' in VO2 that has been reported following the onset of moderate-intensity (below the gas exchange threshold, GET) exercise in endurance athletes. Seven trained endurance cyclists and seven trained endurance runners completed six square-wave transitions to a work-rate or running speed requiring 80% of mode-specific GET during both cycle and treadmill running exercise. The kinetics of VO2 was assessed using non-linear regression and any overshoot in VO2 was quantified as the integrated volume (IV) of O-2 Consumed above the steady-state requirement. During cycling, an overshoot in VO2 was evident in all seven cyclists (IV = 136 +/- 41 ml) and in four runners (IV = 81 +/- 94 ml). During running, an overshoot in VO2 was evident in four runners (IV = 72 +/- 61 ml) but no cyclists. These data challenge the notion that VO2 always rises towards a steady-state with near-exponential kinetics in this exercise intensity domain. The greater incidence of the VO2 overshoot during cycling (11/14 subjects) compared to running (4/14 subjects) indicates that the overshoot phenomenon is related to an interaction between high levels of aerobic fitness and exercise modality. We speculate that a transient loss in muscle efficiency as a consequence of a non-constant ATP requirement following the onset of constant-work-rate exercise or an initially excessive recruitment of motor units (relative to the work-rate) might contribute to the overshoot phenomenon. (c) 2007 Elsevier B.V. All rights reserved.
Abstract.
Kilding AE, Jones AM (2008). over(V, ̇)<inf>O2</inf> 'overshoot' during moderate-intensity exercise in endurance-trained athletes: the influence of exercise modality.
Respiratory Physiology and Neurobiology,
160(2), 139-146.
Abstract:
over(V, ̇)O2 'overshoot' during moderate-intensity exercise in endurance-trained athletes: the influence of exercise modality
The purpose of this study was to investigate the influence of exercise modality on the 'overshoot' in over(V, ̇)O2 that has been reported following the onset of moderate-intensity (below the gas exchange threshold, GET) exercise in endurance athletes. Seven trained endurance cyclists and seven trained endurance runners completed six square-wave transitions to a work-rate or running speed requiring 80% of mode-specific GET during both cycle and treadmill running exercise. The kinetics of over(V, ̇)O2 was assessed using non-linear regression and any overshoot in over(V, ̇)O2 was quantified as the integrated volume (IV) of O2 consumed above the steady-state requirement. During cycling, an overshoot in over(V, ̇)O2 was evident in all seven cyclists (IV = 136 ± 41 ml) and in four runners (IV = 81 ± 94 ml). During running, an overshoot in over(V, ̇)O2 was evident in four runners (IV = 72 ± 61 ml) but no cyclists. These data challenge the notion that over(V, ̇)O2 always rises towards a steady-state with near-exponential kinetics in this exercise intensity domain. The greater incidence of the over(V, ̇)O2 overshoot during cycling (11/14 subjects) compared to running (4/14 subjects) indicates that the overshoot phenomenon is related to an interaction between high levels of aerobic fitness and exercise modality. We speculate that a transient loss in muscle efficiency as a consequence of a non-constant ATP requirement following the onset of constant-work-rate exercise or an initially excessive recruitment of motor units (relative to the work-rate) might contribute to the overshoot phenomenon. © 2007 Elsevier B.V. All rights reserved.
Abstract.
Jones AM, Wilkerson DP, Vanhatalo A, Burnley M (2007). A 'Fast-start' Pacing Strategy Enhances Performance During High-intensity Exercise. Medicine & Science in Sports & Exercise, 39(5).
Wilkerson DP, Jones AM (2007). Effects of Baseline Metabolic Rate on Pulmonary O2 Uptake On-kinetics During Heavy-intensity Exercise in Humans. Medicine & Science in Sports & Exercise, 39(5).
Wilkerson DP, Jones AM (2007). Effects of baseline metabolic rate on pulmonary O2 uptake on-kinetics during heavy-intensity exercise in humans.
Respir Physiol Neurobiol,
156(2), 203-211.
Abstract:
Effects of baseline metabolic rate on pulmonary O2 uptake on-kinetics during heavy-intensity exercise in humans.
We hypothesised that initiating heavy-intensity exercise from an elevated baseline metabolic rate would result in slower Phase II O2 uptake V(O2) kinetics and a greater overall 'gain' in V(O2) per unit increase in work rate. Seven healthy males performed a series of like-transitions on a cycle ergometer: (1) from light exercise to 'moderate' exercise (80% of the gas exchange threshold, GET; L-->M); (2) from light exercise to 'heavy' exercise (40% of the difference between GET and V(O2) peak; L-->H); (3) from moderate exercise to heavy exercise (M-->H). The Phase II time constant (tau) was significantly (PH condition (48+/-11 s) compared to the L-->M and L-->H conditions (26+/-6 s versus 27+/-4 s, respectively). Moreover, the end-exercise 'gain' values were significantly different between the three conditions (L-->M, 8.1+/-0.7 mL min-1 W-1; L-->H, 9.7+/-0.4 mL min-1 W-1; M-->H, 10.7+/-0.7 mL min-1 W-1; P
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Author URL.
Jones AM, Wilkerson DP, Berger NJ, Fulford J (2007). Influence of endurance training on muscle [PCr] kinetics during high-intensity exercise.
Am J Physiol Regul Integr Comp Physiol,
293(1), R392-R401.
Abstract:
Influence of endurance training on muscle [PCr] kinetics during high-intensity exercise.
We hypothesized that a period of endurance training would result in a speeding of muscle phosphocreatine concentration ([PCr]) kinetics over the fundamental phase of the response and a reduction in the amplitude of the [PCr] slow component during high-intensity exercise. Six male subjects (age 26 +/- 5 yr) completed 5 wk of single-legged knee-extension exercise training with the alternate leg serving as a control. Before and after the intervention period, the subjects completed incremental and high-intensity step exercise tests of 6-min duration with both legs separately inside the bore of a whole-body magnetic resonance spectrometer. The time-to-exhaustion during incremental exercise was not changed in the control leg [preintervention group (PRE): 19.4 +/- 2.3 min vs. postintervention group (POST): 19.4 +/- 1.9 min] but was significantly increased in the trained leg (PRE: 19.6 +/- 1.6 min vs. POST: 22.0 +/- 2.2 min; P < 0.05). During step exercise, there were no significant changes in the control leg, but end-exercise pH and [PCr] were higher after vs. before training. The time constant for the [PCr] kinetics over the fundamental exponential region of the response was not significantly altered in either the control leg (PRE: 40 +/- 13 s vs. POST: 43 +/- 10 s) or the trained leg (PRE: 38 +/- 8 s vs. POST: 40 +/- 12 s). However, the amplitude of the [PCr] slow component was significantly reduced in the trained leg (PRE: 15 +/- 7 vs. POST: 7 +/- 7% change in [PCr]; P < 0.05) with there being no change in the control leg (PRE: 13 +/- 8 vs. POST: 12 +/- 10% change in [PCr]). The attenuation of the [PCr] slow component might be mechanistically linked with enhanced exercise tolerance following endurance training.
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Author URL.
Burnley M, Jones AM (2007). Oxygen uptake kinetics as a determinant of sports performance.
EUR J SPORT SCI,
7(2), 63-79.
Abstract:
Oxygen uptake kinetics as a determinant of sports performance
It is well known that physiological variables such as maximal oxygen uptake (VO2max), exercise economy, the lactate threshold, and critical power are highly correlated with endurance exercise performance. In this review, we explore the basis for these relationships by explaining the influence of these "traditional'' variables on the dynamic profiles of the V.O-2 response to exercise of different intensities, and how these differences in V.O-2 dynamics are related to exercise tolerance and fatigue. The existence of a ``slow component'' of V.O-2 during exercise above the lactate threshold reduces exercise efficiency and mandates a greater consumption of endogenous fuel stores (chiefly muscle glycogen) for muscle respiration. For higher exercise intensities (above critical power), steady states in blood acid-base status and pulmonary gas exchange are not attainable and V.O-2 will increase with time until V.O-2max is reached. Here, we show that it is the interaction of the V.O-2 slow component, V.O-2max, and the "anaerobic capacity'' that determines the exercise tolerance. Essentially, we take the view that an appreciation of the various exercise intensity "domains'' and their characteristic effects on V.O-2 dynamics can be helpful in improving our understanding of the determinants of exercise tolerance and the limitations to endurance sports performance. The reciprocal effects of interventions such as training, prior exercise, and manipulations of muscle oxygen availability on aspects of V.O-2 kinetics and exercise tolerance are consistent with this view.
Abstract.
Jones AM, Berger NJ, Wilkerson DP, Campbell IT (2007). Plasma volume expansion does not influence oxygen uptake kinetics in trained cyclists - Reply to Zavorsky. J APPL PHYSIOL, 102(2), 829-829.
Berger NJA, Jones AM (2007). Pulmonary O-2 uptake on-kinetics in sprint- and endurance-trained athletes.
APPL PHYSIOL NUTR ME,
32(3), 383-393.
Abstract:
Pulmonary O-2 uptake on-kinetics in sprint- and endurance-trained athletes
Pulmonary O-2 uptake kinetics during "step" exercise have not been characterized in young, sprint-trained (SPT), athletes. Therefore, the objective of this study was to test the hypotheses that SPT athletes would have (i) slower phase II kinetics and (ii) a greater oxygen uptake "slow component" when compared with endurance-trained (ENT) athletes. Eight sub-elite SPT athletes (mean ( +/- SD) age = 25 (+/- 7) y; mass = 80.3 (+/- 7.3) kg) and 8 sub-elite ENT athletes (age = 28 (+/- 4) y; mass = 73.2 (+/- 5.1) kg) completed a ramp incremental cycle ergometer test, a Wingate 30 s anaerobic sprint test, and repeat "step" transitions in work rate from 20 W to moderate- and severe-intensity cycle exercise, during which pulmonary oxygen uptake was measured breath by breath. The phase II oxygen uptake kinetics were significantly slower in the SPT athletes both for moderate (time constant, tau; SPT 32 (+/- 4) s vs. ENT 17 (+/- 3) s; p < 0.01) and severe (SPT 32 (+/- 12) s vs. ENT 20 (+/- 6) s; p < 0.05) exercise. The amplitude of the slow component (derived by exponential modelling) was not significantly different between the groups (SPT 0.55 (+/- 0.12) L-min(-1) vs. ENT 0.50 (+/- 0.22) L-min(-1)), but the increase in oxygen uptake between 3 and 6 min of severe exercise was greater in the SPT athletes (SPT 0.37 (+/- 0.08) L-min(-1) vs. ENT 0.20 (+/- 0.09) L-min(-1); p < 0.01). The phase II tau was significantly correlated with indices of aerobic exercise performance (e.g. peak oxygen uptake (moderate-intensity r = -0.88, p < 0.01; severe intensity r = -0.62; p < 0.05), whereas the relative amplitude of the oxygen uptake slow component was significantly correlated with indices of anaerobic exercise performance (e.g. Wingate peak power output; r = 0.77; p < 0.01). Thus, it could be concluded that Sub-elite SPT athletes have slower phase II oxygen uptake kinetics and a larger oxygen uptake slow component compared with sub-elite ENT athletes. It appears that indices of aerobic and anaerobic exercise performance differentially influence the fundamental and slow components of the oxygen uptake kinetics.
Abstract.
Jones AM, Berger NJ, Wilkerson DP, Campbell IT (2007). Reply to Zavorsky [14]. Journal of Applied Physiology, 102(2).
Poole DC, Ferreira LF, Behnke BJ, Barstow TJ, Jones AM (2007). The final frontier: Oxygen flux into muscle at exercise onset.
EXERC SPORT SCI REV,
35(4), 166-173.
Abstract:
The final frontier: Oxygen flux into muscle at exercise onset
In humans at exercise onset, intramuscular phosphocreatine decreases immediately, whereas muscle oxygen (O-2) uptake seems to rise after a delay of up to 15 s which is inconsistent with models of metabolic control. Novel microcirculatory investigations reveal that elevated capillary-to-myocyte O-2 flux in rat muscle is, in fact, initiated simultaneously with contractions.
Abstract.
Midgley AW, McNaughton LR, Jones AM (2007). Training to enhance the physiological determinants of long-distance running performance: can valid recommendations be given to runners and coaches based on current scientific knowledge? (vol 37, pg 875, 2007). SPORTS MED, 37(11), 1000-1000.
Midgley AW, McNaughton LR, Jones AM (2007). Training to enhance the physiological determinants of long-distance running performance: can valid recommendations be given to runners and coaches based on current scientific knowledge?.
Sports Med,
37(10), 857-880.
Abstract:
Training to enhance the physiological determinants of long-distance running performance: can valid recommendations be given to runners and coaches based on current scientific knowledge?
This article investigates whether there is currently sufficient scientific knowledge for scientists to be able to give valid training recommendations to long-distance runners and their coaches on how to most effectively enhance the maximal oxygen uptake, lactate threshold and running economy. Relatively few training studies involving trained distance runners have been conducted, and these studies have often included methodological factors that make interpretation of the findings difficult. For example, the basis of most of the studies was to include one or more specific bouts of training in addition to the runners' 'normal training', which was typically not described or only briefly described. The training status of the runners (e.g. off-season) during the study period was also typically not described. This inability to compare the runners' training before and during the training intervention period is probably the main factor that hinders the interpretation of previous training studies. Arguably, the second greatest limitation is that only a few of the studies included more than one experimental group. Consequently, there is no comparison to allow the evaluation of the relative efficacy of the particular training intervention. Other factors include not controlling the runners' training load during the study period, and employing small sample sizes that result in low statistical power. Much of the current knowledge relating to chronic adaptive responses to physical training has come from studies using sedentary individuals; however, directly applying this knowledge to formulate training recommendations for runners is unlikely to be valid. Therefore, it would be difficult to argue against the view that there is insufficient direct scientific evidence to formulate training recommendations based on the limited research. Although direct scientific evidence is limited, we believe that scientists can still formulate worthwhile training recommendations by integrating the information derived from training studies with other scientific knowledge. This knowledge includes the acute physiological responses in the various exercise domains, the structures and processes that limit the physiological determinants of long-distance running performance, and the adaptations associated with their enhancement. In the future, molecular biology may make an increasing contribution in identifying effective training methods, by identifying the genes that contribute to the variation in maximal oxygen uptake, the lactate threshold and running economy, as well as the biochemical and mechanical signals that induce these genes. Scientists should be cautious when giving training recommendations to runners and coaches based on the limited available scientific knowledge. This limited knowledge highlights that characterising the most effective training methods for long-distance runners is still a fruitful area for future research.
Abstract.
Author URL.
Jones AM, Berger NJA, Wilkerson DP, Roberts CL (2006). Effects of "priming" exercise on pulmonary O2 uptake and muscle deoxygenation kinetics during heavy-intensity cycle exercise in the supine and upright positions.
J Appl Physiol (1985),
101(5), 1432-1441.
Abstract:
Effects of "priming" exercise on pulmonary O2 uptake and muscle deoxygenation kinetics during heavy-intensity cycle exercise in the supine and upright positions.
We hypothesized that the performance of prior heavy exercise would speed the phase 2 oxygen consumption (VO2) kinetics during subsequent heavy exercise in the supine position (where perfusion pressure might limit muscle O2 supply) but not in the upright position. Eight healthy men (mean +/- SD age 24 +/- 7 yr; body mass 75.0 +/- 5.8 kg) completed a double-step test protocol involving two bouts of 6 min of heavy cycle exercise, separated by a 10-min recovery period, on two occasions in each of the upright and supine positions. Pulmonary O2 uptake was measured breath by breath and muscle oxygenation was assessed using near-infrared spectroscopy (NIRS). The NIRS data indicated that the performance of prior exercise resulted in hyperemia in both body positions. In the upright position, prior exercise had no significant effect on the time constant tau of the VO2 response in phase 2 (bout 1: 29 +/- 10 vs. bout 2: 28 +/- 4 s; P = 0.91) but reduced the amplitude of the VO2 slow component (bout 1: 0.45 +/- 0.16 vs. bout 2: 0.22 +/- 0.14 l/min; P = 0.006) during subsequent heavy exercise. In contrast, in the supine position, prior exercise resulted in a significant reduction in the phase 2 tau (bout 1: 38 +/- 18 vs. bout 2: 24 +/- 9 s; P = 0.03) but did not alter the amplitude of the VO2 slow component (bout 1: 0.40 +/- 0.29 vs. bout 2: 0.41 +/- 0.20 l/min; P = 0.86). These results suggest that the performance of prior heavy exercise enables a speeding of phase 2 VO2 kinetics during heavy exercise in the supine position, presumably by negating an O2 delivery limitation that was extant in the control condition, but not during upright exercise, where muscle O2 supply was probably not limiting.
Abstract.
Author URL.
Jones AM, Berger NJ, Wilkerson DP, Campbell IT (2006). Influence of Acute Plasma Volume Expansion on Oxygen Uptake Kinetics in Severe-Intensity Exercise.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
38(5), S114-S114.
Author URL.
Wilkerson DP, Berger NJA, Jones AM (2006). Influence of Hyperoxia on Pulmonary O(2) Uptake On-Kinetics During Moderate, Heavy and Supra-Maximal Intensity Exercise in Humans.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
38(5), S382-S382.
Author URL.
Berger NJA, Campbell IT, Wilkerson DP, Jones AM (2006). Influence of acute plasma volume expansion on VO2 kinetics, VO2 peak, and performance during high-intensity cycle exercise.
J APPL PHYSIOL,
101(3), 707-714.
Abstract:
Influence of acute plasma volume expansion on VO2 kinetics, VO2 peak, and performance during high-intensity cycle exercise
The purpose of this study was to examine the influence of acute plasma volume expansion (APVE) on oxygen uptake (Vo(2)) kinetics, Vo(2) (peak), and time to exhaustion during severe-intensity exercise. Eight recreationally active men performed "step" cycle ergometer exercise tests at a work rate requiring 70% of the difference between the gas-exchange threshold and Vo(2) (max) on three occasions: twice as a "control" (Con) and once after intravenous infusion of a plasma volume expander (Gelofusine; 7 ml/kg body mass). Pulmonary gas exchange was measured breath by breath. APVE resulted in a significant reduction in hemoglobin concentration (preinfusion: 16.0 +/- 1.0 vs. postinfusion: 14.7 +/- 0.8 g/dl; P < 0.001) and hematocrit (preinfusion: 44 +/- 2 vs. postinfusion: 41 +/- 3%; P < 0.01). Despite this reduction in arterial O-2 content, APVE had no effect on Vo(2) kinetics ( phase II time constant, Con: 33 +/- 15 vs. APVE: 34 +/- 12 s; P = 0.74), and actually resulted in an increased Vo(2 peak) ( Con: 3.90 +/- 0.56 vs. APVE: 4.12 +/- 0.55 l/min; P = 0.006) and time to exhaustion ( Con: 365 +/- 58 vs. APVE: 424 +/- 64 s; P = 0.04). The maximum O-2 pulse was also enhanced by the treatment ( Con: 21.3 +/- 3.4 vs. APVE: 22.7 +/- 3.4 ml/beat; P = 0.04). In conclusion, APVE does not alter Vo(2) kinetics but enhances Vo(2 peak) and exercise tolerance during high-intensity cycle exercise in young recreationally active subjects.
Abstract.
Burnley M, Roberts CL, Thatcher R, Doust JH, Jones AM (2006). Influence of blood donation on O-2 uptake on-kinetics, peak O-2 uptake and time to exhaustion during severe-intensity cycle exercise in humans.
EXP PHYSIOL,
91(3), 499-509.
Abstract:
Influence of blood donation on O-2 uptake on-kinetics, peak O-2 uptake and time to exhaustion during severe-intensity cycle exercise in humans
We hypothesized that the reduction of O-2-carrying capacity caused by the withdrawal of similar to 450 ml blood would result in slower phase IIO2 uptake V-O2 kinetics, a lower. V-O2 peak and a reduced time to exhaustion during severe-intensity cycle exercise. Eleven healthy subjects (mean +/- S.D. age 23 +/- 6 years, body mass 77.2 +/- 11.0 kg) completed 'step' exercise tests from unloaded cycling to a severe-intensity work rate (80% of the difference between the predetermined gas exchange threshold and the. V-O2 peak) on two occasions before, and 24 h following, the voluntary donation of similar to 450 ml blood. Oxygen uptake was measured breath-by-breath, and. V-O2 kinetics estimated using non-linear regression techniques. The blood withdrawal resulted in a significant reduction in haemoglobin concentration (pre: 15.4 +/- 0.9 versus post: 14.7 +/- 1.3 g dl(-1); 95% confidence limits (CL): -0.04, -1.38) and haematocrit (pre: 44 +/- 2 versus post: 41 +/- 3%; 95% CL: -1.3, -5.1). Compared to the control condition, blood withdrawal resulted in significant reductions in. V(O2)peak (pre: 3.79 +/- 0.64 versus post: 3.64 +/- 0.61 l min-(1); 95% CL: -0.04, -0.27) and time to exhaustion (pre: 375 +/- 129 versus post: 321 +/- 99 s; 95% CL: -24, -85). However, the kinetic parameters of the fundamental. V-O2 response, including the phase II time constant (pre: 29 +/- 8 versus post: 30 +/- 6 s; 95% CL: 5, -3), were not altered by blood withdrawal. The magnitude of the. VO2 slow component was significantly reduced following blood donation owing to the lower. V-O2 peak attained. We conclude that a reduction in blood O-2-carrying capacity, achieved through the withdrawal of similar to 450 ml blood, results in a significant reduction in. V(O2)peak and exercise tolerance but has no effect on the fundamental phase of the. V-O2 on-kinetics during severe-intensity exercise.
Abstract.
Berger NJA, Tolfrey K, Williams AG, Jones AM (2006). Influence of continuous and interval training on oxygen uptake on-kinetics.
MED SCI SPORT EXER,
38(3), 504-512.
Abstract:
Influence of continuous and interval training on oxygen uptake on-kinetics
Purpose: to examine the relative effectiveness of moderate-intensity continuous training and high-intensity interval training on pulmonary O-2 uptake (VO2) kinetics at the onset of moderate- and severe-intensity cycle exercise in previously sedentary subjects. Methods: Twenty-three healthy subjects (I I males; mean +/- SD age 24 +/- 5 yr; VO2peak 34.3 +/- 5.5 mL(.)kg(-1.)min(-1)) were assigned to one of three groups: a continuous training group that completed three to four sessions per week of 30-min duration at 60% VO2peak (LO); an interval training group that completed three to four sessions per week involving 20 x 1-min exercise bouts at 90% VO2peak separated by 1-min rest periods (HI); or a control group (CON). Before and after the 6-wk intervention period, all subjects completed a series of step exercise tests to moderate and severe work rates during which pulmonary VO2 was measured breath-by-breath. Results: ANOVA revealed that continuous and interval training were similarly effective in reducing the phase II VO2 time constant during moderate (LO: from 31 +/- 8 to 23 +/- 5 s; HI: from 32 +/- 9 to 21 +/- 4 s; both P < 0.05; CON: from 30 +/- 6 to 29 +/- 7 s; NSD) and severe exercise (LO: from 35 +/- 6 to 24 +/- 7 s; HI: from 32 +/- 11 to 24 +/- 7 s; both P < 0.05; CON: from 27 +/- 7 to 25 +/- 5 s; NSD) and in reducing the amplitude of the VO2 slow component (LO: from 0.38 +/- 0.10 to 0.29 +/- 0.09 L(.)min(-1); HI: from 0.41 +/- 0.28 to 0.30 +/- 0.28 L(.)min(-1); both P < 0.05; CON: from 0.54 +/- 0.22 to 0.66 +/- 0.38 L(.)min(-1); NSD). Conclusions: Six weeks of low-intensity continuous training and high-intensity interval training were similarly effective in enhancing VO2 on-kinetics following step transitions to moderate and severe exercise in previously untrained subjects.
Abstract.
Smith PM, McCrindle E, Doherty M, Price MJ, Jones AM (2006). Influence of crank rate on the slow component of pulmonary O(2) uptake during heavy arm-crank exercise.
Appl Physiol Nutr Metab,
31(3), 292-301.
Abstract:
Influence of crank rate on the slow component of pulmonary O(2) uptake during heavy arm-crank exercise.
The principal aim of this study was to examine the influence of variations in crank rate on the slow component of the pulmonary oxygen uptake ((.)VO(2)) response to heavy-intensity arm-crank ergometry (ACE). We hypothesized that, for the same external work rate, a higher crank rate would elicit a greater amplitude of the (.)VO(2) "slow component". Eleven healthy males (mean (+/- SD) age, 25 ((+/-6) y; body mass, 89.1 ((+/-10.7) kg; ACE (.)VO(2)(peak), 3.36 ((+/-0.47) L x min(-1)) volunteered to participate. The subjects initially completed an incremental exercise test for the determination of (.)VO(2)(peak) and peak power on an electrically braked arm ergometer. Subsequently, they completed "step" transitions from an unloaded baseline to a work rate requiring 70% of peak power: 2 at a crank rate of 50 r x min(-1) (LO) and 2 at a crank rate of 90 r x min(-1) (HI). Pulmonary gas exchange was measured on a breath-by-breath basis and (.)VO(2) kinetics were evaluated from the mean response to each condition using non-linear regression techniques. In contradiction to our hypothesis, the (.)VO(2) slow component was significantly greater at 50 r x min(-1) than at 90 r x min(-1) (LO: 0.60 +/- 0.30 vs. HI: 0.47 +/- 0.21 L x min(-1); p < 0.05). The mean value for the localized rating of perceived exertion was also higher at 50 r x min(-1) than at 90 r x min(-1) (LO: 16.7 +/- 1.4 vs. HI: 15.2 +/- 1.3; p < 0.05), but there was no significant difference in end-exercise blood lactate concentration. It is possible that differences in muscle tension development and blood flow resulted in a greater contribution of "low-efficiency" type II muscle fibres to force production at the lower crank rate in ACE, and that this was linked to the greater (.)VO(2) slow component. However, other factors such as greater isometric contraction of the muscles of the trunk and legs at the lower crank rate might also be implicated.
Abstract.
Author URL.
Wilkerson DP, Berger NJA, Jones AM (2006). Influence of hyperoxia on pulmonary O2 uptake kinetics following the onset of exercise in humans. Respiratory Physiology & Neurobiology, 153(1), 92-106.
Wilkerson DP, Jones AM (2006). Influence of initial metabolic rate on pulmonary O2 uptake on-kinetics during severe intensity exercise.
Respir Physiol Neurobiol,
152(2), 204-219.
Abstract:
Influence of initial metabolic rate on pulmonary O2 uptake on-kinetics during severe intensity exercise.
We hypothesised that the fundamental (Phase II) component of pulmonary oxygen uptake (VO(2)) kinetics would be significantly slower when step transitions to severe intensity cycle exercise were initiated from elevated baseline metabolic rates, and that this would be associated with evidence for a greater activation of higher-order (i.e. type II) muscle fibres. Seven male subjects (age 22-34 years) completed repeat step transitions to a severe (S) work rate, estimated to require 100% VO(2) peak, from a baseline of: (1) 3 min of unloaded cycling (L-->S); (2) 6 min of moderate exercise (M-->S); (3) 6 min of heavy exercise (H-->S). Pulmonary gas exchange and the electromyogram (EMG) of the m. vastus lateralis were measured throughout all exercise tests. The Phase II VO(2) kinetics became progressively slower at higher baseline metabolic rates (tau was 37 +/- 6, 59 +/- 23, and 93 +/- 50 s for L-->S, M-->S, and H-->S, respectively; P < 0.05 between L-->S and H-->S). Both the integrated EMG and the mean power frequency were significantly higher immediately before the step transition to severe exercise when it was initiated from higher metabolic rates. Although indirect, these data suggest that the slower Phase II VO(2) kinetics observed at higher baseline metabolic rates was related to alterations in muscle activation and fibre recruitment patterns.
Abstract.
Author URL.
McDonough P, Jones AM, Poole DC (2006). Nitric oxide and muscle Vo(2) kinetics. J PHYSIOL-LONDON, 573(2), 565-566.
Burnley M, Wilkerson DP, Jones AM (2006). Point: Counterpoint: Cardiovascular variability is/is not an index of autonomic control of circulation. J APPL PHYSIOL, 101(2), 683-683.
Berger NJA, Rittweger J, Kwietz A, Michaelis I, Williams AG, Tolfrey K, Jones AM (2006). Pulmonary O-2 uptake on-kinetics in enduranceand sprint-trained master athletes.
INT J SPORTS MED,
27(12), 1005-1012.
Abstract:
Pulmonary O-2 uptake on-kinetics in enduranceand sprint-trained master athletes
The purpose of this study was to characterise the VO2 kinetic response to moderate intensity cycle exercise in endurance-trained (END) and sprint or power-trained (SPR) track and field master athletes ranging in age from 45 to 85 years. We hypothesised that the time constant (T) describing the Phase II VO2 on-response would be smaller in the END compared to the SPR athletes, and that the T would become greater with increasing age in both groups. Eighty-four master athletes who were competing at either the British or European Veteran Athletics Championships acted as subjects, and were classified as either END (800 m - marathon; n = 41), or SPR (100-400 m and field events; n = 43) specialists. Subjects completed two 6 minute "step" transitions to a work rate of moderate intensity on a cycle ergometer and pulmonary gas exchange was measured breath-by-breath. Analysis of variance revealed that SPR athletes had slower VO2 on-kinetics (i.e. greater t) compared to END athletes at each of the age groups studied: 46-55 yrs (END: 25 +/- 6 vs. SPR: 36 +/- 9 s; p < 0.10), 56-65 yrs (END: 25 p < 0.10), 56-65 yrs (END: 25 5 vs. SPR: 35 +/- 10 s; p < 0.05), 66 +/- 75 5 vs. SPR: 35 +/- 10 s; p < 0.05), 66-75 yrs (END: 29yrs (END: 29 10 vs. SPR: 40 +/- 13 s; 10 vs. SPR: 40 +/- 13 s; p < 0.05), and 76-85 yrs (END: 31 10 vs. SPR: 51 18 s; p < 0.05). The VO2 on-kinetics became slower with advancing age in the SPR athletes (p < 0.05 between 56-65 and 76-85 yrs) but were not significantly changed in the END athletes. The slower VO2 on-kinetics in SPR compared to END master athletes is consistent both with differences in physiology (e.g. muscle fibre type, oxidative/glycolytic capacity) and training between these specialist athletes. Master END athletes have similar T values to their younger counterparts (similar to 25 s) suggesting that participation in endurance exercise training limits the slowing of VO2 on-kinetics with age in this population.
Abstract.
Berger NJA, McNaughton LR, Keatley S, Wilkerson DP, Jones AM (2006). Sodium bicarbonate ingestion alters the slow but not the fast phase of VO2 kinetics.
MED SCI SPORT EXER,
38(11), 1909-1917.
Abstract:
Sodium bicarbonate ingestion alters the slow but not the fast phase of VO2 kinetics
Purpose: the influence of metabolic alkalosis (ALK) on pulmonary O-2 uptake (pVO(2)) kinetics during high-intensity cycle exercise is controversial. The purpose of this study was to examine the influence of ALK induced by sodium bicarbonate (NaHCO3) ingestion on pVO(2) kinetics, using a sufficient number of repeat-step transitions to provide high confidence in the results obtained. Methods: Seven healthy males completed step tests to a work rate requiring 80% pVO(2max) on six separate occasions: three times after ingestion of 0.3 g(.)kg(-1) body mass NaHCO3 in 1 L of fluid, and three times after ingestion of a placebo (CON). Blood samples were taken to assess changes in acid-base balance, and pVO(2) was measured breath-by-breath. Results: NaHCO3 ingestion significantly increased blood pH and [bicarbonate] both before and during exercise relative to the control condition (P < 0.001). The time constant of the phase II pVO(2) response was not different between conditions (CON: 29 +/- 6 vs ALK: 32 +/- 7 s; P = 0.21). However, the onset of the pVO(2) Slow component was delayed by NaHCO3 ingestion (CON: 120 +/- 19 vs ALK: 147 34 s; P < 0.01), resulting in a significantly reduced end-exercise pVO(2) (CON: 2.88 +/- 0.19 vs ALK: 2.79 +/- 0.23 L(.)min(-1); P < 0.05). Conclusions: Metabolic alkalosis has no effect on phase II pVO(2) kinetics but alters the pVO(2) slow-component response, possibly as a result of the effects of NaHCO3 ingestion on muscle pH.
Abstract.
Smith PM, Amaral I, Doherty M, Price MJ, Jones AM (2006). The influence of ramp rate on VO2peak and "excess" VO2 during arm crank ergometry.
Int J Sports Med,
27(8), 610-616.
Abstract:
The influence of ramp rate on VO2peak and "excess" VO2 during arm crank ergometry.
The principal aim of this study was to examine how different ramp rates influenced the attainment of peak physiological responses during incremental arm crank ergometry (ACE). Additionally, the study examined whether there was any evidence for the development of an "excess" VO (2) during ACE due to upward curvi-linearity in the VO (2)-work rate relationship, and whether this was influenced by the ramp rate. Sixteen physically active, though non-specifically trained, men (mean +/- S age 30 +/- 8 years; height 1.79 +/- 0.07 m; body mass 84.7 +/- 13.2 kg) volunteered to participate. Having completed a familiarisation test, all subjects returned to the laboratory to complete two ramp tests on an electrically-braked ergometer in a counter-balanced order. Both ramp tests started at 60 W with work rate subsequently incremented by either 6 or 12 W. min (-1). Pulmonary gas exchange was measured breath-by-breath throughout the tests. Subjects achieved a greater final work rate during the 12 W. min (-1) test compared to the 6 W. min (-1) test (168 +/- 28 vs. 149 +/- 26 W; p < 0.001). The VO (2peak) (3.06 +/- 0.65 vs. 2.96 +/- 0.48 L. min (-1); p = 0.27), HR (peak) (179 +/- 15 vs. 177 +/- 16 b. min (-1); p = 0.17) and V.E (peak) (112 +/- 22 vs. 105 +/- 16 L. min (-1); p = 0.09) were not different between the tests, but VCO (2peak) (3.54 +/- 0.64 vs. 3.27 +/- 0.46 L. min (-1); p = 0.01) RER (peak) (1.17 +/- 0.07 vs. 1.11 +/- 0.06; p < 0.001), and end-exercise blood (lactate) (11.9 +/- 2.1 vs. 10.8 +/- 2.6 mmol. L (-1); p = 0.005) were all higher in the 12 W. min (-1) test. An "excess" VO (2) was observed in 13 out of 16 tests at 12 W. min (-1) and in 15 out of 16 tests at 6 W. min (-1). Neither the magnitude of the "excess" VO (2) (0.42 +/- 0.41 vs. 0.37 +/- 0.18 L. min (-1); p = 0.66) nor the VO (2) at which the V.O (2)-work rate relationship departed from linearity (2.17 +/- 0.34 vs. 2.18 +/- 0.32 L. min (-1); p = 0.94) were significantly different between the two ramp tests. These data indicate that differences in ramp rate within the range of 6 - 12 W. min (-1) influence the peak values of work rate, VCO (2) and RER, but do not influence peak values of VO (2) or HR during ACE. The development of an "excess" VO (2) appears to be a common feature of ramp exercise in ACE, although the mechanistic basis for this effect is presently unclear.
Abstract.
Author URL.
Jones AM (2006). The physiology of the world record holder for the women's marathon. International Journal of Sports Science and Coaching, 101-116.
Burnley M, Doust JH, Jones AM (2006). Time required for the restoration of normal heavy exercise Vo(2) kinetics following prior heavy exercise.
J APPL PHYSIOL,
101(5), 1320-1327.
Abstract:
Time required for the restoration of normal heavy exercise Vo(2) kinetics following prior heavy exercise
Prior heavy exercise markedly alters the 02 uptake (Vo(2)) response to subsequent heavy exercise. However, the time required for Vo(2) to return to its normal profile following prior heavy exercise is not known. Therefore, we examined the Vo(2) responses to repeated bouts of heavy exercise separated by five different recovery durations. On separate occasions, nine male subjects completed two 6-min bouts of heavy cycle exercise separated by 10, 20, 30, 45, or 60 min of passive recovery. The second-by-second VO2 responses were modeled using nonlinear regression. Prior heavy exercise had no effect on the primary VO2 time constant (from 25.9 +/- 4.7 s to 23.9 +/- 8.8 s after 10 min of recovery; P = 0.338), but it increased the primary Vo(2) amplitude (from 2.42 +/- 0.39 to 2.53 +/- 0.41 l/min after 10 min of recovery; P = 0.001) and reduced the Vo(2) slow component (from 0.44 +/- 0.13 to 0.21 +/- 0.12 l/min after 10 min of recovery; P < 0.001). The increased primary amplitude was also evident after 20-45 min, but not after 60 min, of recovery. The increase in the primary Vo(2) amplitude was accompanied by an increased baseline blood lactate concentration (to 5.1 +/- 1.0 mM after 10 min of recovery; P < 0.001). Baseline blood lactate concentration was still elevated after 20 - 60 min of recovery. The priming effect of prior heavy exercise on the Vo(2) response persists for at least 45 min, although the mechanism underpinning the effect remains obscure.
Abstract.
Jones AM, Koppo K (2005). Chasing the "ghost" of the acetyl group deficit - Response. MED SCI SPORT EXER, 37(1), 163-163.
Timmons JA, Jones AM, Koppo K (2005). Chasing the "ghost" of the acetyl group deficit [1] (multiple letters). Medicine and Science in Sports and Exercise, 37(1), 162-163.
Burnley M, Jones AM (2005). Effect of warm-up exercise on energy provision and exercise performance in horses and humans: a comparative review. Equine and Comparative Exercise Physiology, 134-147.
Burnley M, Doust JH, Jones AM (2005). Effects of Prior Warm-up Regime on Severe Intensity Cycling Performance. Medicine & Science in Sports & Exercise, 37(Supplement).
Burnley M, Doust JH, Jones AM (2005). Effects of Prior Warm-up Regime on Severe Intensity Cycling Performance.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
37, S79-S79.
Author URL.
Burnley M, Doust JH, Jones AM (2005). Effects of prior warm-up regime on severe-intensity cycling performance.
MED SCI SPORT EXER,
37(5), 838-845.
Abstract:
Effects of prior warm-up regime on severe-intensity cycling performance
Purpose: the purpose of the present study was to determine the effect of three different warm-up regimes on cycling work output during a 7-min performance trial. Methods: After habituation to the experimental methods, 12 well-trained cyclists completed a series of 7-min performance trials, involving 2 min of constant-work rate exercise at &SIM; 90% VO2max and a further 5 min during which subjects attempted to maximize power output. This trial was performed without prior intervention and 10 min after bouts of moderate, heavy, or sprint exercise in a random order. Pulmonary gas exchange was measured breath by breath during all performance trials. Results: at the onset of the performance trial, baseline blood [lactate] was significantly elevated after heavy and sprint but not moderate exercise (mean &PLUSMN; SD: control, 1.0 &PLUSMN; 0.3 mM; moderate, 1.0 &PLUSMN; 0.2 mM; heavy, 3.0 &PLUSMN; 1.1 mM; sprint, 5.9 &PLUSMN; 1.5 mM). All three interventions significantly increased the amplitude of the primary VO2 response (control, 2.59 &PLUSMN; 0.28 L-min(-1); moderate, 2.69 &PLUSMN; 0.27 L-min(-1); heavy, 2.78 &PLUSMN; 0.26 L-min(-1); sprint, 2.78 &PLUSMN; 0.30 L-min(-1)). Mean power output was significantly increased by prior moderate and heavy exercise but not significantly reduced after sprint exercise (control, 330 42 W; moderate, 338 &PLUSMN; 39 W; heavy, 339 &PLUSMN; 42 W; sprint, 324 &PLUSMN; 45 W). Conclusions: These data indicate that priming exercise performed in the moderate- and heavy-intensity domains can improve severe-intensity cycling performance by &SIM; 2-3%, the latter condition doing so despite a mild lactacidosis being present at exercise onset.
Abstract.
Martin JA, Tolfrey K, Smith NC, Jones AM (2005). Heart rate responses of rugby union referees in the English Premiership.
J HUM MOVEMENT STUD,
48(3), 211-225.
Abstract:
Heart rate responses of rugby union referees in the English Premiership
Relatively little is known about the physiological demands placed upon referees during high-level rugby union matches. The purpose of this study was therefore to describe, for the first time, the heart rate (HR) responses of referees during rugby union matches in the English Premiership. Thirteen 'elite' referees (ranked in the top 20 referees in England, aged 34-51 years) had their HR recorded by telemetry during 1-4 matches. Within 2-3 weeks of these measurements they also completed a laboratory-based physiological assessment of their HR, (V) over dot o(2) and blood lactate responses to incremental treadmill exercise. The mean +/- SD HR of the referees during match play was 153 +/- 9b.min(-1) (equivalent to 84 +/- 5% of HR max). It was estimated from the individual regression equations of HR on (V) over dot O-2 derived from the incremental treadmill tests that the mean (V) over dot O-2 during match play was 3.17+/-0.40L.min(-1) (equivalent to 79 +/- 6% (V) over dot O-2 max). There was no significant difference in the mean HR recorded in the first and second halves of a match. High-level ruby union match refereeing is physically demanding and this should be taken into account in the assessment and development of task-specific fitness in rugby union referees.
Abstract.
Jones AM, Wilkerson DP, Naish P, Rittweger J (2005). Influence of recombinant human erythropoietin treatment on pulmonary O2 uptake kinetics during exercise in humans. The Journal of Physiology, 568(2), 639-652.
Jones AM, Poole DC (2005). Oxygen uptake dynamics: from muscle to mouth--an introduction to the symposium.
Med Sci Sports Exerc,
37(9), 1542-1550.
Abstract:
Oxygen uptake dynamics: from muscle to mouth--an introduction to the symposium.
The purpose of this paper is to provide an introduction to the study of oxygen uptake (VO(2)) dynamics or kinetics. Following the onset of exercise, both muscle and pulmonary VO(2) rise in a near-exponential fashion towards the anticipated "steady-state" VO(2) demand. However, it can take 2-4 min, or even longer at higher work rates, before this steady state is attained. Slow VO(2) kinetics increase the so-called O(2) deficit and obligate a greater contribution from anaerobic mechanisms of ATP production (involving the breakdown of muscle high energy phosphates and lactate production from glycogen) to meet the ATP requirement of the exercise task. A primary goal in this area of research is therefore to elucidate the physiological mechanisms which control and/or limit the rate at which muscle VO(2) increases following the onset of exercise. At higher intensities of exercise, a continued increase in both muscle and pulmonary VO(2) is observed with time despite the external work rate remaining constant. This continued rise in VO(2), beyond the anticipated steady-state requirement for the work rate, has been termed the VO(2) "slow component," and establishing the mechanistic basis for this phenomenon is another important goal of research in this field. This paper provides an overview of some of the factors which might contribute to both the fundamental and slow phases of the VO(2) kinetics and, in so doing, provides general background material for the more specific papers that follow.
Abstract.
Author URL.
Poole DC, Kindig CA, Behnke BJ, Jones AM (2005). Oxygen uptake kinetics in different species: a brief review. Equine and Comparative Exercise Physiology, 1-15.
Berger NJ, Rittweger J, Tolfrey K, Jones AM (2005). Pulmonary O(2) Uptake Kinetics in Sprint and Endurance Trained Master Athletes.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
37, S362-S362.
Author URL.
Berger NJ, Rittweger J, Tolfrey K, Jones AM (2005). Pulmonary O2 Uptake Kinetics in Sprint and Endurance Trained Master Athletes. Medicine & Science in Sports & Exercise, 37(Supplement).
Roberts CL, Wilkerson DP, Jones AM (2005). Pulmonary O2 uptake on-kinetics in rowing and cycle ergometer exercise.
Respir Physiol Neurobiol,
146(2-3), 247-258.
Abstract:
Pulmonary O2 uptake on-kinetics in rowing and cycle ergometer exercise.
The purpose of this study was to characterise, for the first time, the pulmonary O2 uptake (V(O2)) on-kinetic responses to step transitions to moderate and heavy intensity rowing ergometer exercise, and to compare the responses to those observed during upright cycle ergometer exercise. We hypothesised that the recruitment of a greater muscle mass in rowing ergometer exercise (Row) might limit muscle perfusion and result in slower Phase II V(O2) kinetics compared to cycle exercise (Cyc). Eight healthy males (aged 28+/-5 years) performed a series of step transitions to moderate (90% of the mode-specific gas exchange threshold, GET) and heavy (50% of the difference between the mode-specific GET and V(O2) max) work rates, for both Row and Cyc exercise. Pulmonary V(O2) was measured breath-by-breath and the V(O2) on-kinetics were described using standard non-linear regression techniques. With the exception of delta V(O2)delta WR which was approximately 12% greater for Row, the V(O2) kinetic responses were similar between the exercise modes. There was no significant difference in the time constant describing the Phase II V(O2) kinetics between the exercise modes for either moderate (rowing: 25.9+/-6.8 s versus cycling: 25.7+/-8.6 s) or heavy (rowing: 26.5+/-3.0 s versus cycling: 27.8+/-5.1s) exercise. Furthermore, there was no significant difference in the amplitude of the V(O2) slow component between the exercise modes (rowing: 0.34+/-0.13 L min(-1) versus cycling: 0.35+/-0.12 L min(-1)). These data suggest that muscle V(O2) increases towards the anticipated steady-state requirement at essentially the same rate following a step increase in ATP turnover in the myocytes, irrespective of the mode of exercise, at least in subjects with no particular sport specialism. The recruitment of a greater muscle mass in rowing compared to cycling apparently did not compromise muscle perfusion sufficiently to result either in slower Phase II V(O2) kinetics or a greater V(O2) slow component amplitude during heavy exercise.
Abstract.
Author URL.
Wilkerson DP, Koppo K, Jones AM (2005). Pulmonary Vo(2) On-kinetic Response to Step Exercise: Influence of Initial Metabolic Rate.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
37, S362-S363.
Author URL.
Kilding A, Jones AM (2005). The Validity of a Single Visit Protocol to Determine the Maximum Lactate Steady State. Medicine & Science in Sports & Exercise, 37(Supplement).
Kilding A, Jones AM (2005). The Validity of a Single Visit Protocol to Determine the Maximum Lactate Steady State.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
37, S101-S101.
Author URL.
Kilding AE, Jones AM (2005). Validity of a single-visit protocol to estimate the maximum lactate steady state.
MED SCI SPORT EXER,
37(10), 1734-1740.
Abstract:
Validity of a single-visit protocol to estimate the maximum lactate steady state
Introduction: the maximum lactate steady state (MLSS) represents the highest intensity of exercise at which a balance exists between the rate of lactate production and the rate of lactate clearance. The MLSS is an important determinant of endurance exercise performance but its determination, which involves 4-5 laboratory visits, is labor-intensive and time consuming. Purpose: to compare the MLSS estimated from a single-visit protocol (MLSSsingle) with the traditional, directly measured MLSS (MLSStrad). Methods: Following an incremental treadmill test for the determination of VO2peak, eight endurance-trained runners completed: 1) a series of 4-5 constant-speed treadmill runs of up to 30-min duration, on separate days, for determination of the MLSStrad; and 2) a single-visit protocol consisting of two constant-speed treadmill runs of 20-min duration at approximately 65 and 90% VOP2peak separated by 40 min of rest, for determination of MLSSsingle. Blood lactate concentration ([La]), oxygen uptake (VO2), and heart rate (HR) were measured every 5 min in all treadmill runs. Comparisons between values were made using paired t-tests. Results: the MLSSsingle significantly underestimated the MLSStrad with respect to speed (13.4 +/- 1.2 vs 16.4 +/- 1.6 km center dot h(-1), P = 0.002), HR (148 +/- 8 vs 170 +/- 10 b center dot min(-1), P < 0.001), blood [La] (2.3 +/- 1.5 vs 3.9 +/- 1.0 mmol center dot L-1; P = 0.01), and %VO2peak utilized (75 +/- 8 vs 90 +/- 2%, P = 0.002). The MLSStrad speed and MLSSsingle speed were poorly correlated (r = 0.29, P = 0.49). Conclusion: the single-visit method of determining the MLSS substantially underestimates the actual MLSS.
Abstract.
Shaw DJ, Holmes PS, Wilkerson DP, Jones AM (2004). Cardiorespiratory responses during observation of heavy intensity exercise. AUST J PSYCHOL, 56, 135-135.
Jones AM, Campbell, I.T. Koppo, K. Wilkerson, D.P. (2004). Dichloroacetate does not speed phase II pulmonary VO2 kinetics following the onset of heavy intensity cycle exercise. Pflugers Archives: European Journal of Physiology, 447(6), 867-874.
Bouckaert J, Jones AM, Koppo K (2004). Effect of glycogen depletion on the oxygen uptake slow component in humans.
Int J Sports Med,
25(5), 351-356.
Abstract:
Effect of glycogen depletion on the oxygen uptake slow component in humans.
Previous studies have indicated that the (.-)VO(2) slow component is related to the recruitment of type II muscle fibres. We therefore hypothesised that an exercise and dietary regimen designed to deplete type I muscle fibres of glycogen would result in a greater contribution of type II muscle fibres to the exercise power output and therefore a larger amplitude of the (.-)VO(2) slow component. Eight male subjects took part in this study. On day 1, the subjects reported to the laboratory at 8 a.m. and completed a 9 min constant-load cycling test at a work rate equivalent to 85 % (.-)VO(2) peak. On day 2 at 12 p.m. the subjects were fed a 4200 kJ meal (60 % protein, 40 % fat); at 6 p.m. they completed a 2 h cycling test at 60 % (.-)VO(2) peak. On day 3 at 8 a.m. the subjects performed an exercise test identical to that of day 1. Metabolic and respiratory measurements indicated that our experimental design was effective in reducing the muscle glycogen content. (.-)VO(2) was significantly higher (by approximately 140 ml x min (-1)) throughout exercise following glycogen depletion but no appreciable changes in (.-)VO(2) kinetics were found: neither the time constant of the primary response (from 35.4 +/- 2.5 to 33.2 +/- 4.4 s) nor the amplitude of the slow component (from 404 +/- 95 to 376 +/- 81 ml x min (-1)) was significantly altered. Therefore, we suggest that the increased (.-)VO(2) throughout exercise and the unaltered (.-)VO(2) slow component following glycogen depletion might be explained by a shift towards a greater reliance on fat metabolism in type I muscle fibres with no appreciable change in fibre type recruitment patterns.
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Author URL.
Wilkerson DP, Koppo K, Barstow TJ, Jones AM (2004). Effect of prior multiple-sprint exercise on pulmonary O2 uptake kinetics following the onset of perimaximal exercise.
J Appl Physiol (1985),
97(4), 1227-1236.
Abstract:
Effect of prior multiple-sprint exercise on pulmonary O2 uptake kinetics following the onset of perimaximal exercise.
We hypothesized that the metabolic acidosis resulting from the performance of multiple-sprint exercise would enhance muscle perfusion and result in a speeding of pulmonary oxygen uptake (VO2)kinetics during subsequent perimaximal-intensity constant work rate exercise, if O2 availability represented a limitation to VO2 kinetics in the control (i.e. no prior exercise) condition. On two occasions, seven healthy subjects completed two bouts of exhaustive cycle exercise at a work rate corresponding to approximately 105% of the predetermined Vo2 peak, separated by 3 x 30-s maximal sprint cycling and 15-min recovery (MAX1 and MAX2). Blood lactate concentration (means +/- SD: MAX1: 1.3 +/- 0.4 mM vs. MAX2: 7.7 +/- 0.9 mM; P < 0.01) was significantly greater immediately before, and heart rate was significantly greater both before and during, perimaximal exercise when it was preceded by multiple-sprint exercise. Near-infrared spectroscopy also indicated that muscle blood volume and oxygenation were enhanced when perimaximal exercise was preceded by multiple-sprint exercise. However, the time constant describing the primary component (i.e. phase II) increase in VO2 was not significantly different between the two conditions (MAX1: 33.8 +/- 5.5 s vs. MAX2: 33.2 +/- 7.7 s). Rather, the asymptotic "gain" of the primary Vo2 response was significantly increased by the performance of prior sprint exercise (MAX1: 8.1 +/- 0.9 ml.min(-1).W(-1) vs. MAX2: 9.0 +/- 0.7 ml.min(-1).W(-1); P < 0.05), such that VO2 was projecting to a higher "steady-state" amplitude with the same time constant. These data suggest that priming exercise, which apparently increases muscle O2 availability, does not influence the time constant of the primary-component VO2 response but does increase the amplitude to which VO2 may rise following the onset of perimaximal-intensity cycle exercise.
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Author URL.
Wilkerson DP, Koppo K, Barstow TJ, Jones AM (2004). Effect of work rate on the functional 'gain' of Phase II pulmonary O2 uptake response to exercise.
Respir Physiol Neurobiol,
142(2-3), 211-223.
Abstract:
Effect of work rate on the functional 'gain' of Phase II pulmonary O2 uptake response to exercise.
It has recently been reported that the 'gain' of Phase II increase in pulmonary oxygen uptake (i.e. the 'fundamental' increase in V(O(2)) per unit increase in work rate; G(p)) does not attain the anticipated value of approximately 10 ml min(-1)W(-1) following the onset of high-intensity exercise. In the present study, we hypothesised that G(p) would fall significantly below 10 ml min(-1)W(-1) only when the work rate exceeded the so-called 'critical power' (CP). Seven healthy males completed several 'square-wave' transitions from 'unloaded' cycling to work rates requiring 60 and 90% of the gas exchange threshold (GET), 40 and 80% of the difference between the GET and V(O(2)) peak (i.e. below and above the CP, respectively), and 100, 110 and 120% of V(O(2)) peak. Pulmonary V(O(2)) was measured breath-by-breath and V(O(2)) kinetics were determined using non-linear regression techniques. The asymptotic G(p) was significantly lower at work rates above (7.2-8.6 ml min(-1)W(-1)) compared to work rates below (9.3-9.7 ml min(-1)W(-1)) the CP (P < 0.05). We conclude that the gain of Phase II increase in V(O(2)) becomes significantly reduced when the work rate exceeds the CP.
Abstract.
Author URL.
Koppo K, Bouckaert J, Jones AM (2004). Effects of training status and exercise intensity on phase II VO2 kinetics.
Med Sci Sports Exerc,
36(2), 225-232.
Abstract:
Effects of training status and exercise intensity on phase II VO2 kinetics.
PURPOSE: to test the hypotheses that: 1) the time constant for the fast component of. VO2 kinetics (tau1) at exercise onset would be faster in trained than in untrained subjects for both moderate and heavy exercise, and that 2) tau1 would become progressively slower in untrained subjects at higher power outputs but be invariant in trained subjects. METHODS: Eight untrained subjects (.VO2peak: 42.9 +/- 5.1 mL.kg-1.min-1) and seven trained cyclists (.VO2peak: 66.6 +/- 2.5 mL.kg-1.min-1) completed square-wave transitions to power outputs requiring 60% and 80% of gas exchange threshold (GET), and 50% of the difference between GET and. VO2 peak (50%Delta) from a baseline of "unloaded" cycling. VO2 was measured breath-by-breath and individual responses were modeled using nonlinear regression techniques. RESULTS: a repeated measures ANOVA revealed that the tau1 was significantly smaller (i.e. the kinetics were faster) in the trained compared with the untrained subjects and that tau1 became significantly greater (i.e. the kinetics were slowed) at higher power outputs both in the untrained (60%GET: 17.8 +/- 3.8 s, 80%GET: 21.5 +/- 6.6 s, and 50%Delta: 23.5 +/- 2.8 s) and the trained (60%GET: 8.9 +/- 1.3 s, 80%GET: 11.7 +/- 2.5 s, and 50%Delta: 15.2 +/- 2.0 s) subjects (P < 0.05). CONCLUSION: Phase II. VO2 kinetics became progressively slower at higher power outputs in both trained and untrained subjects. That a greater tau1 was evident at a higher power output within the moderate exercise intensity domain (
Abstract.
Author URL.
Pringle JSM, Doust JH, Carter H, Tolfrey K, Campbell IT, Sakkas GK, Jones AM (2004). Erratum: Oxygen uptake kinetics during moderate, heavy and severe intensity 'submaximal' exercise in humans: the influence of muscle fibre type and capillarisation (European Journal of Applied Physiology (2004) vol. 89 (289-300) 10.1007/s00421-003-0799-1). European Journal of Applied Physiology, 92(1-2).
Koppo K, Wilkerson DP, Bouckaert J, Wilmshurst S, Campbell IT, Jones AM (2004). Influence of DCA on pulmonary (.-)V(O2) kinetics during moderate-intensity cycle exercise.
Med Sci Sports Exerc,
36(7), 1159-1164.
Abstract:
Influence of DCA on pulmonary (.-)V(O2) kinetics during moderate-intensity cycle exercise.
PURPOSE: to test the hypothesis that pharmacological activation of the pyruvate dehydrogenase enzyme complex (PDC) with dichloroacetate (DCA) would speed phase II pulmonary oxygen uptake ((.-)V(O2)) kinetics after the onset of subsequent moderate-intensity (40-45% ((.-)V(O2)) peak) cycle exercise. METHODS: Seven healthy males (mean +/- SD age 25 +/- 4 yr, body mass 75.3 +/- 9.4 kg) performed four "square-wave" transitions from unloaded cycling to a work rate requiring 90% of the predetermined gas exchange threshold either with or without prior infusion of DCA (50 mg x kg body mass in 50 mL saline). Pulmonary ((.-)V(O2)) was measured breath-by-breath in all tests and ((.-)V(O2)) kinetics were determined from the averaged individual response to each condition using nonlinear regression techniques. RESULTS: the blood [lactate] measured immediately before the onset of exercise was significantly reduced in the DCA condition (C: 1.1 +/- 0.3 vs DCA: 0.6 +/- 0.3 mM; P < 0.01) consistent with successful activation of the PDC. However, DCA had no discernible effect on the rate at which ((.-)V(O2)) increased toward the steady state after the onset of exercise as reflected in the phase II time constant (C: 28.5 +/- 11.8 vs DCA: 29.4 +/- 14.9 s). CONCLUSIONS: the results suggest that PDC activation does not represent a principal intramuscular limitation to ((.-)V(O2)) kinetics after the onset of moderate-intensity exercise.
Abstract.
Author URL.
Jones AM, Wilkerson DP, Wilmshurst S, Campbell IT (2004). Influence of L-NAME on pulmonary O2 uptake kinetics during heavy-intensity cycle exercise.
J Appl Physiol (1985),
96(3), 1033-1038.
Abstract:
Influence of L-NAME on pulmonary O2 uptake kinetics during heavy-intensity cycle exercise.
We hypothesized that inhibition of nitric oxide synthase (NOS) by N(G)-nitro-L-arginine methyl ester (L-NAME) would alleviate the inhibition of mitochondrial oxygen uptake (Vo(2)) by nitric oxide and result in a speeding of phase II pulmonary Vo(2) kinetics at the onset of heavy-intensity exercise. Seven men performed square-wave transitions from unloaded cycling to a work rate requiring 40% of the difference between the gas exchange threshold and peak Vo(2) with and without prior intravenous infusion of L-NAME (4 mg/kg in 50 ml saline over 60 min). Pulmonary gas exchange was measured breath by breath, and Vo(2) kinetics were determined from the averaged response to two exercise bouts performed in each condition. There were no significant differences between the control (C) and L-NAME conditions (L) for baseline Vo(2), the duration of phase I, or the amplitude of the primary Vo(2) response. However, the time constant of the Vo(2) response in phase II was significantly smaller (mean +/- SE: C: 25.1 +/- 3.0 s; L: 21.8 +/- 3.3 s; P < 0.05), and the amplitude of the Vo(2) slow component was significantly greater (C: 240 +/- 47 ml/min; L: 363 +/- 24 ml/min; P < 0.05) after L-NAME infusion. These data indicate that inhibition of NOS by L-NAME results in a significant (13%) speeding of Vo(2) kinetics and a significant increase in the amplitude of the Vo(2) slow component in the transition to heavy-intensity cycle exercise in men. The speeding of the primary component Vo(2) kinetics after L-NAME infusion indicates that at least part of the intrinsic inertia to oxidative metabolism at the onset of heavy-intensity exercise may result from inhibition of mitochondrial Vo(2) by nitric oxide. The cause of the larger Vo(2) slow-component amplitude with L-NAME requires further investigation but may be related to differences in muscle blood flow early in the rest-to-exercise transition.
Abstract.
Author URL.
Jones AM, Campbell IT, Pringle JSM (2004). Influence of muscle fibre type and pedal rate on the VO2-work rate slope during ramp exercise.
Eur J Appl Physiol,
91(2-3), 238-245.
Abstract:
Influence of muscle fibre type and pedal rate on the VO2-work rate slope during ramp exercise.
We hypothesised that the ratio between the increase in oxygen uptake and the increase in work rate (Delta VO(2)/DeltaWR) during ramp cycle exercise would be significantly related to the percentage type II muscle fibres at work rates above the gas exchange threshold (GET) where type II fibres are presumed to be active. We further hypothesised that ramp exercise at higher pedal rates, which would be expected to increase the proportional contribution of type II fibres to the total power delivered, would increase the Delta VO(2)/DeltaWR slope at work rates above the GET. Fourteen healthy subjects [four female; mean (SD): age 25 (3) years, body mass 74.3 (15.1) kg] performed a ramp exercise test to exhaustion (25 W min(-1)) at a pedal rate of 75 rev min(-1), and consented to a muscle biopsy of the vastus lateralis. Eleven of the subjects also performed two further ramp tests at pedal rates of 35 and 115 rev min(-1). The Delta VO(2)/DeltaWR slope for exercise
Abstract.
Author URL.
Wilkerson DP, Campbell IT, Jones AM (2004). Influence of nitric oxide synthase inhibition on pulmonary O2 uptake kinetics during supra-maximal exercise in humans. The Journal of Physiology, 561(2), 623-635.
Wilkerson DP, Campbell IT, Jones AM (2004). Influence of nitric oxide synthase inhibition on pulmonary O2 uptake kinetics during supra-maximal exercise in humans.
J Physiol,
561(Pt 2), 623-635.
Abstract:
Influence of nitric oxide synthase inhibition on pulmonary O2 uptake kinetics during supra-maximal exercise in humans.
We have recently reported that inhibition of nitric oxide synthase (NOS) with N(G)-nitro-L-arginine methyl ester (L-NAME) accelerates the 'phase II' pulmonary O2 uptake (VO2) kinetics following the onset of moderate and heavy intensity submaximal exercise in humans. These data suggest that the influence of nitric oxide (NO) on mitochondrial function is an important factor in the inertia to aerobic respiration that is evident in the transition from a lower to a higher metabolic rate. The purpose of the present study was to investigate the influence of L-NAME on pulmonary VO2 kinetics following the onset of supra-maximal exercise, where it has been suggested that O2 availability represents an additional limitation to VO2 kinetics. Seven healthy young men volunteered to participate in this study. Following an incremental cycle ergometer test for the determination of VO2max, the subjects returned on two occasions to perform a 'step' exercise test from a baseline of unloaded cycling to a work rate calculated to require 105% VO2max, preceded either by systemic infusion of L-NAME (4 mg kg(-1) in 50 ml saline) or 50 ml saline as a control (Con). Pulmonary gas exchange was measured on a breath-by-breath basis throughout the exercise tests. The duration of 'phase I' was greater with L-NAME (Con: 14.0 +/- 2.1 versus L-NAME: 16.0 +/- 1.6 s; P = 0.03), suggestive of a slower cardiovascular adaptation following the onset of exercise. However, the phase II VO2 time constant was reduced by 44% with L-NAME (Con: 36.3 +/- 17.3 versus L-NAME: 20.4 +/- 8.3 s; P = 0.01). The accumulation of blood lactate during exercise was also reduced with L-NAME (Con: 4.0 +/- 1.1 versus L-NAME: 2.7 +/- 2.1 mM; P = 0.04). These data indicate that skeletal muscle NO production represents an important limitation to the acceleration of oxidative metabolism following the onset of supra-maximal exercise in humans.
Abstract.
Author URL.
Tolfrey K, Jones AM, Campbell IG (2004). Lipid-lipoproteins in children: an exercise dose-response study.
Med Sci Sports Exerc,
36(3), 418-427.
Abstract:
Lipid-lipoproteins in children: an exercise dose-response study.
PURPOSE: to study the effect of exercise volume on pre- and early-pubertal children's lipid-lipoprotein profile. METHODS: Thirty-four children (15 girls) completed 12 wk of exercise training, preceded by a 12-wk control period. Sixteen (7 girls and 9 boys) expended an additional 422 +/- 5 kJ.kg BM (LOW, 100 kcal.kg), whereas 18 (8 girls and 10 boys) expended an additional 586 +/- 7 kJ.g (MOD, 140 kcal.kg) as a result of the training program. They all exercised on three nonconsecutive days per week at 80 +/- 1% HRpeak. Exercise duration was individualized to match energy expenditure targets. Plasma TG, TC, and HDL-C were measured precontrol, pretraining, and posttraining. LDL-C, TC/HDL-C, and LDL-C/HDL-C were also calculated. RESULTS: Group mean lipid-lipoprotein concentrations did not change as a result of training energy expenditure in either of the groups (P > 0.05). Dietary composition, habitual physical activity, and body composition were also relatively stable over the intervention period (P > 0.05). In the LOW, but not the MOD group, peak VO2 (mL.kg.min) tended to increase over the intervention period (P = 0.07). Pearson's product moment correlation analyses indicated that pretraining concentrations of TG, TC, LDL-C, TC/HDL-C, and LDL-C/HDL-C were all related to the small changes seen in the lipid-lipoprotein profile (P < 0.01). CONCLUSION: Additional energy expenditure of 422 or 586 kJ.kg, as a direct result of aerobic exercise training over a 12-wk period, did not cause significant alterations in the lipid-lipoprotein profile in pre- and early-pubertal children. This may indicate that the exercise volume was insufficient, the lipoprotein profiles of the majority of children in this study were classified as "desirable," or more likely a combination of these factors.
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Author URL.
Almarwaey OA, Jones AM, Tolfrey K (2004). Maximal lactate steady state in trained adolescent runners.
J Sports Sci,
22(2), 215-225.
Abstract:
Maximal lactate steady state in trained adolescent runners.
The aims of this study were: (1) to identify the exercise intensity that corresponds to the maximal lactate steady state in adolescent endurance-trained runners; (2) to identify any differences between the sexes; and (3) to compare the maximal lactate steady state with commonly cited fixed blood lactate reference parameters. Sixteen boys and nine girls volunteered to participate in the study. They were first tested using a stepwise incremental treadmill protocol to establish the blood lactate profile and peak oxygen uptake (VO2). Running speeds corresponding to fixed whole blood lactate concentrations of 2.0, 2.5 and 4.0 mmol x l(-1) were calculated using linear interpolation. The maximal lactate steady state was determined from four separate 20-min constant-speed treadmill runs. The maximal lactate steady state was defined as the fastest running speed, to the nearest 0.5 km x h(-1), where the change in blood lactate concentration between 10 and 20 min was < 0.5 mmol x l(-1). Although the boys had to run faster than the girls to elicit the maximal lactate steady state (15.7 vs 14.3 km x h(-1), P < 0.01), once the data were expressed relative to percent peak VO2 (85 and 85%, respectively) and percent peak heart rate (92 and 94%, respectively), there were no differences between the sexes (P > 0.05). The running speed and percent peak VO2 at the maximal lactate steady state were not different to those corresponding to the fixed blood lactate concentrations of 2.0 and 2.5 mmol x l(-1) (P > 0.05), but were both lower than those at the 4.0 mmol x l(-1) concentration (P < 0.05). In conclusion, the maximal lactate steady state corresponded to a similar relative exercise intensity as that reported in adult athletes. The running speed, percent peak VO2 and percent peak heart rate at the maximal lactate steady state are approximated by the fixed blood lactate concentration of 2.5 mmol x l(-1) measured during an incremental treadmill test in boys and girls.
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Author URL.
Carter H, Pringle JSM, Boobis L, Jones AM, Doust JH (2004). Muscle glycogen depletion alters oxygen uptake kinetics during heavy exercise.
Med Sci Sports Exerc,
36(6), 965-972.
Abstract:
Muscle glycogen depletion alters oxygen uptake kinetics during heavy exercise.
PURPOSE: to test the hypothesis that muscle fiber recruitment patterns influence the oxygen uptake (VO2) kinetic response, constant-load exercise was performed after glycogen depletion of specific fiber pools. METHODS: After validation of protocols for the selective depletion of Type I and II muscle fibers, 19 subjects performed square-wave exercise at 80% VT (moderate) and at 50% of the difference between VT and VO2max (heavy) without any prior depleting exercise (CON), after HIGH (10 x 1-min exercise bouts at 120% VO2max), and after LOW (3 h of exercise at 30% VO2max) exercise. RESULTS: Differences in VO2 kinetic parameters were only observed in heavy exercise AFTER HIGH: the VO2 primary component was higher (1.75 +/- 0.12 L x min) compared with CON (1.65 +/- 0.11 L x min, P < 0.05), and the VO2 slow component was lower (0.18 +/- 0.03 L x min) compared with CON (0.24 +/- 0.04 L x min, P < 0.05). CONCLUSIONS: the results indicate that the VO2 response to heavy constant-load exercise can be altered by depletion of glycogen in the Type II muscle fibers, lending support to the theory that muscle fiber recruitment influences both the VO2 primary and slow component amplitudes during heavy intensity exercise.
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Author URL.
Jones AM, Wilkerson DP, Campbell IT (2004). Nitric oxide synthase inhibition with L-NAME reduces maximal oxygen uptake but not gas exchange threshold during incremental cycle exercise in man.
J Physiol,
560(Pt 1), 329-338.
Abstract:
Nitric oxide synthase inhibition with L-NAME reduces maximal oxygen uptake but not gas exchange threshold during incremental cycle exercise in man.
We hypothesized that the effective inhibition of nitric oxide synthase (NOS), achieved via systemic infusion of N(G)-nitro-l-arginine methyl ester (l-NAME), would reduce the gas exchange threshold (GET) and the maximal oxygen uptake (V(.)(O(2)max)) during incremental cycle exercise in man if NO is important in the regulation of muscle vasodilatation. Seven healthy males, aged 18-34 years, volunteered to participate in this ethically approved study. On two occasions, the subjects completed an incremental exercise test to exhaustion on an electrically braked cycle ergometer following the infusion of either l-NAME (4 mg kg(-1) in 50 ml saline) or placebo (50 ml saline, CON). At rest, the infusion of l-NAME resulted in a significant increase in mean arterial pressure (MAP; CON vs. l-NAME, 89 +/- 8 vs. 103 +/- 11 mmHg (mean +/- s.d.; P < 0.05)) and a significant reduction in heart rate (HR; CON vs. l-NAME, 60 +/- 12 vs. 51 +/- 8 beats min(-1); P < 0.01). At submaximal work rates, there was no significant difference in V(.)(O(2)) between the conditions and no difference in the GET (CON vs. l-NAME, 1.94 +/- 0.47 vs. 2.01 +/- 0.41 l min(-1)). However, at higher work rates, differences in V(.)(O(2)) between the conditions became more pronounced such that V(.)(O(2)max) was significantly lower with l-NAME (CON vs. l-NAME, 4.02 +/- 0.41 vs. 3.80 +/- 0.34 l min(-1); P < 0.05). The reduction in V(.)(O(2)max) was associated with a reduction in HR(max) (CON vs. l-NAME, 186 +/- 10 vs. 178 +/- 7 beats min(-1); P < 0.01). These results demonstrate that NOS inhibition with l-NAME has no effect on GET but reduces V(.)(O(2)max) during large muscle group exercise in man, presumably by direct or indirect effects on cardiac output and muscle blood flow.
Abstract.
Author URL.
Koppo K, Whipp BJ, Jones AM, Aeyels D, Bouckaert J (2004). Overshoot in VO2 following the onset of moderate-intensity cycle exercise in trained cyclists.
Eur J Appl Physiol,
93(3), 366-373.
Abstract:
Overshoot in VO2 following the onset of moderate-intensity cycle exercise in trained cyclists.
We have previously observed that following the onset of moderate intensity cycle ergometry, the pulmonary O2 uptake (VO2) in trained cyclists often does not increase towards its steady-state value with the typical mono-exponential characteristics; rather, there is a transient "overshoot". The purpose of this study was to systematically examine this phenomenon by comparing the VO2 responses to two moderate-intensity work rates and one high-intensity work rate in trained and untrained subjects. Following a ramp exercise test to the limit of tolerance for the determination of the gas exchange threshold (GET) and VO2(peak), seven trained cyclists [mean (SD); VO2(peak) 66.6 (2.5) ml x kg(-1) x min(-1)] and eight sedentary subjects [VO2(peak) 42.9 (5.1) ml x kg(-1) x min(-1)] completed six step transitions from baseline cycling to work rates requiring 60% and 80% GET and three step transitions from baseline cycling to a work rate requiring 50% of the difference between GET and VO2(peak) (50%delta). VO2 was measured breath-by-breath and modelled using standard techniques. The sedentary subjects did not overshoot the steady-state VO2 at any intensity. At 60% GET, six of the seven cyclists overshot the steady-state VO2 [by an integral volume of 164 (44) ml between approximately 45 and 125 s]. At 80% GET, four of the seven cyclists overshot the steady-state VO2 [by an integral volume of 185 (92) ml between approximately 55 and 140 s]. None of the cyclists showed an overshoot at 50%delta. These results indicate that trained cyclists evidence an overshoot in VO2 before steady-state is reached in the transition to moderate-intensity exercise. The mechanism(s) responsible for this effect remains to be elucidated, as does whether the overshoot confers any functional or performance benefit to the trained cyclist.
Abstract.
Author URL.
Pringle JSM, Doust JH, Carter H, Tolfrey K, Campbell IT, Sakkas GK, Jones AM (2004). Oxygen uptake kinetics during moderate, heavy and severe intensity 'submaximal' exercise in humans: the influence of muscle fibre type and capillarisation (vol 89, pg 289, 2003). EUR J APPL PHYSIOL, 92(1-2), 232-232.
Jones AM, Carter H (2004). Oxygen uptake-work rate relationship during two consecutive ramp exercise tests.
Int J Sports Med,
25(6), 415-420.
Abstract:
Oxygen uptake-work rate relationship during two consecutive ramp exercise tests.
The performance of prior high intensity constant work rate (CWR) exercise significantly influences the gain of the fundamental oxygen uptake (VO2) response during subsequent high intensity CWR exercise. The purpose of the present study was to investigate whether equivalent effects could be elicited in the second of two bouts of exhaustive ramp exercise. We therefore hypothesised that a prior bout of exhaustive ramp exercise would increase the VO2-work rate (DeltaVO2/DeltaWR) slope during subsequent ramp exercise. Nine healthy males performed two ramp exercise tests to exhaustion on an electrically braked cycle ergometer separated by a 10-min period of cycling at 20 W. Pulmonary VO2 was measured breath-by-breath throughout both tests, and the mean response time (MRT) and the DeltaVO2/DeltaWR slope for exercise below the gas exchange threshold (GET) (S1), above the GET (S2), and over the S1 + S2 region (ST) were determined. Paired t-tests were used to analyse the data with significance accepted at p < 0.05. Blood [lactate] was higher at the onset of the second ramp test compared to the first (mean +/- SEM 1.2 +/- 0.1 vs. 6.2 +/- 0.7 mM; p < 0.01), but baseline VO2 was not significantly different between tests (0.93 +/- 0.05 vs. 0.99 +/- 0.06 L. min (-1)). The MRT (42 +/- 4 vs. 40 +/- 5 s) did not differ between tests, but the DeltaVO2/DeltaWR slope was steeper in the second ramp test for S2 (9.1 +/- 0.4 vs. 9.8 +/- 0.5 ml. min (-1). W (-1); p < 0.01) and ST (9.0 +/- 0.4 vs. 9.6 +/- 0.5 ml. min (-1). W (-1); p < 0.05). The demonstration that prior ramp exercise increases the DeltaVO2/DeltaWR slope during subsequent ramp exercise is consistent with the results of previous CWR studies and indicates that exercise economy is sensitive to the prior activity of the engaged muscles.
Abstract.
Author URL.
Pringle JSM, Doust JH, Carter H, Tolfrey K, Jones AM (2003). Effect of pedal rate on primary and slow-component oxygen uptake responses during heavy-cycle exercise.
J Appl Physiol (1985),
94(4), 1501-1507.
Abstract:
Effect of pedal rate on primary and slow-component oxygen uptake responses during heavy-cycle exercise.
We hypothesized that a higher pedal rate (assumed to result in a greater proportional contribution of type II motor units) would be associated with an increased amplitude of the O(2) uptake (Vo(2)) slow component during heavy-cycle exercise. Ten subjects (mean +/- SD, age 26 +/- 4 yr, body mass 71.5 +/- 7.9 kg) completed a series of square-wave transitions to heavy exercise at pedal rates of 35, 75, and 115 rpm. The exercise power output was set at 50% of the difference between the pedal rate-specific ventilatory threshold and peak Vo(2), and the baseline power output was adjusted to account for differences in the O(2) cost of unloaded pedaling. The gain of the Vo(2) primary component was significantly higher at 35 rpm compared with 75 and 115 rpm (mean +/- SE, 10.6 +/- 0.3, 9.5 +/- 0.2, and 8.9 +/- 0.4 ml. min(-1). W(-1), respectively; P < 0.05). The amplitude of the Vo(2) slow component was significantly greater at 115 rpm (328 +/- 29 ml/min) compared with 35 rpm (109 +/- 30 ml/min) and 75 rpm (202 +/- 38 ml/min) (P < 0.05). There were no significant differences in the time constants or time delays associated with the primary and slow components across the pedal rates. The change in blood lactate concentration was significantly greater at 115 rpm (3.7 +/- 0.2 mM) and 75 rpm (2.8 +/- 0.3 mM) compared with 35 rpm (1.7 +/- 0.4 mM) (P < 0.05). These data indicate that pedal rate influences Vo(2) kinetics during heavy exercise at the same relative intensity, presumably by altering motor unit recruitment patterns.
Abstract.
Author URL.
Koppo K, Jones AM, Bouckaert J (2003). Effect of prior heavy arm and leg exercise on VO2 kinetics during heavy leg exercise.
Eur J Appl Physiol,
88(6), 593-600.
Abstract:
Effect of prior heavy arm and leg exercise on VO2 kinetics during heavy leg exercise.
The aim of the present study was to examine the effect of prior exercise at a remote site on the VO(2) kinetics during subsequent heavy cycle exercise using a model that allowed us to discriminate between the VO(2) fast and slow component responses. Ten male subjects completed a constant-load exercise of 6 min cycling at 90% of the VO(2)peak in three conditions: without prior exercise (LE-C), after heavy cycling exercise (6 min at 90% of the VO(2)peak) (LE-L) and after heavy arm-cranking exercise (6 min at 90% of the arm VO(2)peak) (LE-A). Subjects performed four repetitions of each exercise protocol, separated by at least 1 day. VO(2) was measured on a breath-by-breath basis and VO(2) kinetics were determined with a biexponential model. There were no significant differences in the VO(2) fast component parameters between LE-C, LE-L and LE-A. However, the VO(2) slow component amplitude was significantly reduced in LE-L and LE-A compared to LE-C, but the reduction was less pronounced in LE-A [the value of the VO(2) slow exponential term at the end of exercise, A(2)', was 657 (SD 200) ml x min(-1) in LE-C versus 384 (SD 136) ml x min(-1) in LE-L and 551 (SD 169) m x min(-1) in LE-A; P
Abstract.
Author URL.
Jones AM, Koppo K, Burnley M (2003). Effects of prior exercise on metabolic and gas exchange responses to exercise.
Sports Med,
33(13), 949-971.
Abstract:
Effects of prior exercise on metabolic and gas exchange responses to exercise.
'Warm-up' activity is almost universally performed by athletes prior to their participation in training or competition. However, relatively little is known about the optimal intensity and duration for such exercise, or about the potential mechanisms primed by warm-up that might enhance performance. Recent studies demonstrate that vigorous warm-up exercise that normally results in an elevated blood and presumably muscle lactate concentration has the potential to increase the aerobic energy turnover in subsequent high-intensity exercise. The reduced oxygen deficit is associated with a reduction in both the depletion of the intramuscular phosphocreatine stores and the rate at which lactic acid is produced. Furthermore, the oxygen uptake 'slow component' that develops during high-intensity, ostensibly submaximal, exercise is attenuated. These factors would be hypothesised to predispose to increased exercise tolerance. Interestingly, the elevation of muscle temperature by prior exercise does not appear to be implicated in the altered metabolic and gas exchange responses observed during subsequent exercise. The physiological mechanism(s) that limit the rate and the extent to which muscle oxygen uptake increases following the onset of exercise, and which are apparently altered by the performance of prior heavy exercise, are debated. However, these mechanisms could include oxygen availability, enzyme activity and/or availability of metabolic substrate, and motor unit recruitment patterns. Irrespective of the nature of the control mechanisms that are influenced, 'priming' exercise has the potential to significantly enhance exercise tolerance and athletic performance. The optimal combination of the intensity, duration and mode of 'warm-up' exercise, and the recovery period allowed before the criterion exercise challenge, remain to be determined.
Abstract.
Author URL.
Jones AM, Koppo K, Wilkerson DP, Campbell IT (2003). Inhibition of nitric oxide synthase by L-NAME speeds VO2 kinetics in the transition to moderate intensity exercise in man. The Journal of Physiology, 552(1), 265-272.
Burnley M, Jones AM (2003). Interpreting Vo(2) kinetics in heavy exercise revisited. J APPL PHYSIOL, 94(6), 2548-2549.
Burnley M, Jones AM, Hughson RL, Tordi N, Perrey S (2003). Interpreting V̇<inf>O2</inf> kinetics in heavy exercise revisited [2] (multiple letters). Journal of Applied Physiology, 94(6), 2548-2550.
Campbell, I.T. Wilkerson, D.P. Jones AM (2003). Nitric oxide synthase inhibition with L-NAME reduces maximal oxygen uptake but not gas exchange threshold during incremental cycle excercise in man. Journal of Physiology, 560, 265-272.
Jones AM, Campbell IT, Carter H, Doust JH (2003). Oxygen uptake kinetics during moderate, heavy and severe intensity 'submaximal' exercise in humans: the influence of muscle fibre type and capillarisation. European Journal of Applied Physiology, 89(3-4), 289-300.
Almarwaey OA, Jones AM, Tolfrey K (2003). Physiological correlates with endurance running performance in trained adolescents.
MED SCI SPORT EXER,
35(3), 480-487.
Abstract:
Physiological correlates with endurance running performance in trained adolescents
Purpose: to examine the relationship between competitive 800-m and 1500-m performance times and a number of physiological variables in a group of endurance-trained, adolescent runners. Methods: Twenty-three boys and 17 girls volunteered to participate in the study. Track-based, running performance times were available for 18 boys and 14 girls for the 800 in, and 16 boys and 13 girls for the 1500 in. The relationships between these times and the following physiological variables were determined: peak (V) over dot O-2, running economy (RE), estimated running speed at peak (V) over dot O-2 v (V) over dot O-2peak, peak and mean anaerobic power, and fixed [BLa-] at 2.0, 2.5, and 4.0 mmol(.)L(-1). Results: RE and v (V) over dot O-2peak were significant independent variables for the boys' 800 m (r = 0.62 and -0.62, P < 0.01). For the girls, once chronological age was partialled out, none of the measured variables were significantly related to 800-m performance. For the 1500-m event, peak (V) over dot O-2, v (V) over dot O-2peak, and the running speed at 2.5 mmol(.)L(-1) (v2.5) were significant independent variables in the boys (r = -0.43, -0.39, and -0.53, P < 0.05) and girls (r = -0.50, -0.61, and -0.54, P < 0.05). In addition, the (V) over dot O-2 at 2.5 mmol.L-1 (V) over dot O-2 2.5) was related to the 1500-m time in the girls (r = -0.54, P < 0.05). Conclusion: the physiological variables that were most strongly correlated with middle-distance running performance were v2.5 and the v (V) over dot O-2 peak. To a lesser extent peak (V) over dot O-2 may also play a role although it is understood that its contribution may be accounted by v (V)over dot O-2peak.
Abstract.
Jones AM, Wilkerson DP, Burnley M, Koppo K (2003). Prior heavy exercise enhances performance during subsequent perimaximal exercise.
Med Sci Sports Exerc,
35(12), 2085-2092.
Abstract:
Prior heavy exercise enhances performance during subsequent perimaximal exercise.
PURPOSE: to test the hypothesis that prior heavy exercise increases the time to exhaustion during subsequent perimaximal exercise. METHODS: Seven healthy males (mean +/- SD 27 +/- 3 yr; 78.4 +/- 0.7 kg) completed square-wave transitions from unloaded cycling to work rates equivalent to 100, 110, and 120% of the work rate at VO2peak (W-[VO2peak) after no prior exercise (control, C) and 10 min after a 6-min bout of heavy exercise at 50% Delta (HE; half-way between the gas exchange threshold (GET) and VO2peak), in a counterbalanced design. RESULTS: Blood [lactate] was significantly elevated before the onset of the perimaximal exercise bouts after prior HE (approximately 2.5 vs approximately 1.1 mM; P < 0.05). Prior HE increased time to exhaustion at 100% (mean +/- SEM. C: 386 +/- 92 vs HE: 613 +/- 161 s), 110% (C: 218 +/- 26 vs HE: 284 +/- 47 s), and 120% (C: 139 +/- 18 vs HE: 180 +/- 29 s) of W-VO2peak, (all P < 0.01). VO2 was significantly higher at 1 min into exercise after prior HE at 110% W-VO2peak (C: 3.11 +/- 0.14 vs HE: 3.42 +/- 0.16 L x min(-1); P < 0.05), and at 1 min into exercise (C: 3.25 +/- 0.12 vs HE: 3.67 +/- 0.15; P < 0.01) and at exhaustion (C: 3.60 +/- 0.08 vs HE: 3.95 +/- 0.12 L x min(-1); P < 0.01) at 120% of W-VO2peak. CONCLUSIONS: This study demonstrate that prior HE, which caused a significant elevation of blood [lactate], resulted in an increased time to exhaustion during subsequent perimaximal exercise presumably by enabling a greater aerobic contribution to the energy requirement of exercise.
Abstract.
Author URL.
Koppo K, Jones AM, Bouckaert J (2003). VO2 OVERSHOOTS THE STEADY-STATE VALUE IN THE TRANSITION TO MODERATE EXERCISE IN TRAINED CYCLISTS. Medicine & Science in Sports & Exercise, 35(5).
Jones AM, Whipp BJ (2002). Bioenergetic constraints on tactical decision making in middle distance running.
Br J Sports Med,
36(2), 102-104.
Abstract:
Bioenergetic constraints on tactical decision making in middle distance running.
BACKGROUND: the highest velocity that a runner can sustain during middle distance races is defined by the intersection of the runner's individual velocity-time curve and the distance-time curve. The velocity-time curve is presumably fixed at the onset of a race; however, whereas the race distance is ostensibly fixed, the actual distance-time curve is not. That is, it is possible for a runner to run further than the race distance if he or she runs wide on bends in track races. In this instance, the point of intersection of the individual velocity-time curve and the distance-time curve will move downwards and to the right, reducing the best average velocity that can be sustained for the distance. METHODS: to illustrate this point, the race tactics used by the gold and silver medallists at 800 m and 5000 m in the Sydney Olympics were analysed. The paths taken by the runners were carefully tracked and the total distance they covered during the races and the average velocity they sustained over the distances they actually covered were calculated. RESULTS: in both the Olympic 800 m and 5000 m finals, for example, the winner was not the runner who ran at the highest average velocity in the race. Rather, the winners of these races were able to husband their metabolic resources to better effect by running closer to the actual race distance. CONCLUSIONS: Race results in middle distance running events are dependent not just on the energetic potential of the runners at the start of the race and their strategy for pace allocation, but also on the effect of their tactical approach to positioning on the total distance covered in the race. Middle distance runners should be conscious of minimising the distance covered in races if they wish to optimise their performance.
Abstract.
Author URL.
Jones AM (2002). Calculation of additional (XS) (V)over-dot-O-2 during incremental exercise. MED SCI SPORT EXER, 34(11), 1859-1859.
Jones AM, Pedersen PK (2002). Calculation of additional (xs) V̇O<inf>2</inf> during incremental exercise (multiple letters). Medicine and Science in Sports and Exercise, 34(11), 1859-1860.
Jones AM, Carter H, Pringle JSM, Campbell IT (2002). Effect of creatine supplementation on oxygen uptake kinetics during submaximal cycle exercise.
J Appl Physiol (1985),
92(6), 2571-2577.
Abstract:
Effect of creatine supplementation on oxygen uptake kinetics during submaximal cycle exercise.
The purpose of this study was to test the effect of oral creatine (Cr) supplementation on pulmonary oxygen uptake (VO(2)) kinetics during moderate [below ventilatory threshold (VT)] and heavy (above VT) submaximal cycle exercise. Nine subjects (7 men; means +/- SD: age 28 +/- 3 yr, body mass 73.2 +/- 5.6 kg, maximal VO(2) 46.4 +/- 8.0 ml. kg(-1). min(-1)) volunteered to participate in this study. Subjects performed transitions of 6-min duration from unloaded cycling to moderate (80% VT; 8-12 repeats) and heavy exercise (50% change; i.e. halfway between VT and maximal VO(2); 4-6 repeats), both in the control condition and after Cr loading, in a crossover design. The Cr loading regimen involved oral consumption of 20 g/day of Cr monohydrate for 5 days, followed by a maintenance dose of 5 g/day thereafter. VO(2) was measured breath by breath and modeled by using two (moderate) or three (heavy) exponential terms. For moderate exercise, there were no differences in the parameters of the VO(2) kinetic response between control and Cr-loaded conditions. For heavy exercise, the time-based parameters of the VO(2) response were unchanged, but the amplitude of the primary component was significantly reduced with Cr loading (means +/- SE: control 2.00 +/- 0.12 l/min; Cr loaded 1.92 +/- 0.10 l/min; P < 0.05) as was the end-exercise VO(2) (control 2.19 +/- 0.13 l/min; Cr loaded 2.12 +/- 0.14 l/min; P < 0.05). The magnitude of the reduction in submaximal VO(2) with Cr loading was significantly correlated with the percentage of type II fibers in the vastus lateralis (r = 0.87; P < 0.01; n = 7), indicating that the effect might be related to changes in motor unit recruitment patterns or the volume of muscle activated.
Abstract.
Author URL.
Koppo K, Jones AM, Vanden Bossche L, Bouckaert J (2002). Effect of prior exercise on VO(2) slow component is not related to muscle temperature.
Med Sci Sports Exerc,
34(10), 1600-1604.
Abstract:
Effect of prior exercise on VO(2) slow component is not related to muscle temperature.
INTRODUCTION: it has been widely reported that the VO(2) slow component is reduced in the second of two bouts of heavy exercise. It has also been shown that an increase in muscle temperature (Tm) produced by wearing hot-water-perfused pants causes a reduction in the VO(2) slow component. Therefore, the aim of this study was to investigate whether the effect of prior heavy exercise on the VO(2) slow component of subsequent heavy exercise is related to the warming-up of the exercising limbs. METHODS: Six male subjects completed an exercise protocol consisting of two constant-load exercise bouts (EX-1 and EX-2) at 90% VO(2peak), separated by 6 min of rest. The Tm of the m. vastus lateralis was measured with an indwelling thermistor. Seven days later, the subjects completed a second exercise protocol consisting of a passive warming-up of the upper legs until the same Tm was reached as after EX-1, followed by a constant-load work bout (EX-3) identical to EX-1 and EX-2. RESULTS: Tm reached comparable levels at the start of EX-2 and EX-3 (37.3 +/- 0.6 degrees C and 37.2 +/- 0.3 degrees C, respectively). The VO(2) slow component (measured as deltaVO(2)(6-2 min)) was reduced by 57% after prior heavy exercise ( < 0.05), whereas no significant reduction was observed after prior passive warming-up. CONCLUSIONS: the results of this study indicate that the reduction in VO(2) slow component observed after prior heavy exercise cannot be explained by an increase in muscle temperature of the upper legs.
Abstract.
Author URL.
Jones AM, Ball D, Burnley M, Doust JH (2002). Effects of prior heavy exercise on VO2 kinetics during heavy exercise are related to changes in muscle activity. Journal of Applied Physiology, 93(1), 167-174.
Burnley M, Doust JH, Jones AM (2002). Effects of prior heavy exercise, prior sprint exercise and passive warming on oxygen uptake kinetics during heavy exercise in humans.
Eur J Appl Physiol,
87(4-5), 424-432.
Abstract:
Effects of prior heavy exercise, prior sprint exercise and passive warming on oxygen uptake kinetics during heavy exercise in humans.
Prior heavy exercise (above the lactate threshold, Th(la)) increases the amplitude of the primary oxygen uptake (VVO(2)) response and reduces the amplitude of the VO(2) slow component during subsequent heavy exercise. The purpose of this study was to determine whether these effects required the prior performance of an identical bout of heavy exercise, or if prior short-duration sprint exercise could cause similar effects. A secondary purpose of this study was to determine the effect of elevating muscle temperature (through passive warming) on VO(2) kinetics during heavy exercise. Nine male subjects performed a 6-min bout of heavy exercise on a cycle ergometer 6 min after: (1) an identical bout of heavy exercise; (2) a 30-s bout of maximal sprint cycling; (3) a 40-min period of leg warming in a hot water bath at 42 degrees C. Prior sprint exercise elevated blood [lactate] prior to the onset of heavy exercise (by aproximately 5.6 mM) with only a minor increase in muscle temperature (of approximately 0.7 degrees C). In contrast, prior warming had no effect on baseline blood lactate concentration, but elevated muscle temperature by approximately 2.6 degrees C. Both prior heavy exercise and prior sprint exercise significantly increased the absolute primary VO(2) amplitude (by approximately 230 ml x min(-1) and 260 ml x min(-1), respectively) and reduced the amplitude of the VO(2) slow component (by approximately 280 ml x min(-1) and 200 ml x min(-1), respectively) during heavy exercise, whereas prior warming had no significant effect on the VO(2) response. We conclude that the VO(2) response to heavy exercise can be markedly altered by both sustained heavy-intensity submaximal exercise and by short-duration sprint exercise that induces a residual acidosis. In contrast, passive warming elevated muscle temperature but had no effect on the VO(2) response.
Abstract.
Author URL.
Tolfrey K, Almarwaey OA, Abbott J, Satherley H, Jones AM (2002). MAXIMUM LACTATE STEADY STATE IN TRAINED ADOLESCENT BOYS AND GIRLS. Medicine & Science in Sports & Exercise, 34(5).
Pringle JSM, Jones AM (2002). Maximal lactate steady state, critical power and EMG during cycling.
Eur J Appl Physiol,
88(3), 214-226.
Abstract:
Maximal lactate steady state, critical power and EMG during cycling.
We hypothesised that: (1) the maximal lactate steady state (MLSS), critical power (CP) and electromyographic fatigue threshold (EMG(FT)) occur at the same power output in cycling exercise, and (2) exercise above the power output at MLSS (P-MLSS) results in continued increases in oxygen uptake (VO(2)), blood lactate concentration ([La]) and integrated electromyogram (iEMG) with time. Eight healthy subjects [mean (SD) age 25 (3) years, body mass 72.1 (8.2) kg] performed a series of laboratory tests for the determination of MLSS, CP and EMG(FT). The CP was determined from four exhaustive trials of between 2 and 15 min duration. The MLSS was determined as the highest power output at which the increase in blood [La] was less than 1.0 mM across the last 20 min of a series of 30-min trials. The EMG(FT) was determined from four trials of 2 min duration at different power outputs. The surface electromyogram was recorded continuously from the vastus lateralis muscle. The CP was significantly higher than the P-MLSS [242 (25) vs. 222 (23) W; P
Abstract.
Author URL.
Koppo K, Bouckaert J, Jones AM (2002). Oxygen uptake kinetics during high-intensity arm and leg exercise.
Respir Physiol Neurobiol,
133(3), 241-250.
Abstract:
Oxygen uptake kinetics during high-intensity arm and leg exercise.
The purpose of the present study was to examine the oxygen uptake kinetics during heavy arm exercise using appropriate modelling techniques, and to compare the responses to those observed during heavy leg exercise at the same relative intensity. We hypothesised that any differences in the response might be related to differences in muscle fibre composition that are known to exist between the upper and lower body musculature. To test this, ten subjects completed several bouts of constant-load cycling and arm cranking exercise at 90% of the mode specific V(O(2)) peak. There was no difference in plasma [lactate] at the end of arm and leg exercise. The time constant of the fast component response was significantly longer in arm exercise compared to leg exercise (mean+/-S.D. 48+/-12 vs. 21+/-5 sec; P < 0.01), while the fast component gain was significantly greater in arm exercise (12.1+/-1.0 vs. 9.2+/-0.5 ml min(-1) W(-1); P < 0.01). The V(O(2)) slow component emerged later in arm exercise (126+/-27 vs. 95+/-20 sec; P < 0.01) and, in relative terms, increased more per unit time (5.5 vs. 4.4% min(-1); P < 0.01). These differences between arm crank and leg cycle exercise are consistent with a greater and/or earlier recruitment of type II muscle fibres during arm crank exercise.
Abstract.
Author URL.
Pringle JSM, Carter H, Doust JH, Jones AM (2002). Oxygen uptake kinetics during horizontal and uphill treadmill running in humans.
Eur J Appl Physiol,
88(1-2), 163-169.
Abstract:
Oxygen uptake kinetics during horizontal and uphill treadmill running in humans.
The aim of this study was to examine the effect of increasing the ratio of concentric to eccentric muscle activation on oxygen uptake (VO(2)) kinetics during treadmill running. Nine subjects [2 women; mean (SD) age 29 (7) years, height 1.77 (0.07) m, body mass 73.0 (7.5) kg] completed incremental treadmill tests to exhaustion at 0% and 10% gradients to establish the gradient-specific ventilatory threshold (VT) and maximal oxygen uptake (VO(2max)). Subsequently, the subjects performed repeated moderate intensity (80% of gradient-specific VT) and heavy intensity (50% of the difference between the gradient specific VT and VO(2max)) square-wave runs with the treadmill gradient set at 0% and 10%. For moderate intensity exercise, there were no significant differences between treadmill gradients for VO(2) kinetics. For heavy intensity exercise, the amplitude of the primary component of VO(2) was not significantly different between 0% and 10% treadmill gradients [mean (SEM) 2,940 (196) compared to 2,869 (156) ml x min(-1), respectively], but the amplitude of the VO(2) slow component was significantly greater at the 10% gradient [283 (43) compared to 397 (37) ml x min(-1); P < 0.05]. These results indicate that the muscle contraction regimen (i.e. the relative contribution of concentric and eccentric muscle action) significantly influences the amplitude of the VO(2) slow component.
Abstract.
Author URL.
Carter H, Pringle JSM, Jones AM, Doust JH (2002). Oxygen uptake kinetics during treadmill running across exercise intensity domains.
Eur J Appl Physiol,
86(4), 347-354.
Abstract:
Oxygen uptake kinetics during treadmill running across exercise intensity domains.
The purpose of the present study was to examine comprehensively the kinetics of oxygen uptake (VO2) during treadmill running across the moderate, heavy and severe exercise intensity domains. Nine subjects [mean (SD age, 27 (7) years; mass, 69.8 (9.0) kg; maximum VO2, VO2max, 4,137 (697) ml x min(-1)] performed a series of "square-wave" rest-to-exercise transitions of 6 min duration at running speeds equivalent to 80% and 100% of the VO2 at lactate threshold (LT; moderate exercise); and at 20%, 40%, 60%, 80% and 100% of the difference between the VO2 at LT and VO2max (delta heavy and severe exercise). Critical velocity (CV) was also determined using four maximal treadmill runs designed to result in exhaustion in 2-15 min. The VO2 response was modelled using non-linear regression techniques. As expected, the amplitude of the VO2 primary component increased with exercise intensity [from 1,868 (136) ml x min-( 1) at 80% LT to 3,296 (218) ml x min-(1) at 100% delta, P < 0.05]. However, there was a non-significant trend for the "gain" of the primary component to decrease as exercise intensity increased [181 (7) ml x kg(-1) x km(-1) at 80% LT to 160 (6) ml x kg(-1) x km(-1) at 100% delta]. The time constant of the primary component was not different between supra-LT running speeds (mean value range = 17.9-19.1 s), but was significantly shorter during the 80% LT trial [12.7 (1.4) s, P < 0. 05]. The VO2 slow component increased with exercise intensity from 139 (39) ml x min(-1) at 20% delta to 487 (57) ml x min(-1) at 80% delta (P < 0.05), but decreased to 317 (84) ml x min(-1) during the 100% delta trial (P < 0.05). During both the 80% delta and 100% delta trials, the VO2 at the end of exercise reached VOmax [4,152 (242) ml x min(-1) and 4,154 (114) ml x min(-1), respectively]. Our results suggest that the "gain" of the primary component is not constant as exercise intensity increases across the moderate, heavy and severe domains of treadmill running. These intensity-dependent changes in the amplitudes and kinetics of the VO2 response profiles may be associated with the changing patterns of muscle fibre recruitment that occur as exercise intensity increases.
Abstract.
Author URL.
Jones AM (2002). Running economy is negatively related to sit-and-reach test performance in international-standard distance runners.
Int J Sports Med,
23(1), 40-43.
Abstract:
Running economy is negatively related to sit-and-reach test performance in international-standard distance runners.
The purpose of this study was to investigate the relationship between running economy (RE) and lower body flexibility. Thirty-four international-standard male distance runners (mean +/- s, age 27 +/- 5 years; body mass 64.9 +/- 4.2 kg; VO(2)max 72.8 +/- 3.7 ml x kg(-1) x min(-1)) gave written consent to participate in this study. The subjects performed an incremental treadmill test for the assessment of RE, lactate threshold and VO(2)max, and the sit-and-reach test was used to assess their general lower body and trunk flexibility. Running speeds below the lactate threshold were used to explore the relationship between running economy and sit-and-reach test performance. At 16.0 km x h(-1), the VO(2) was 50.6 +/- 3.7 ml x kg(-1) x min(-1) (range: 44.2 to 57.1 ml x kg(-1) x min(-1)). Pearson product moment correlation coefficients revealed no significant relationships between aerobic demand at 16.0 km x h(-1) and age (r = - 0.19), height (r = 0.15), body mass (r = - 0.18), or VO(2)max (r = - 0.004). However, there was a highly significant relationship between aerobic demand at 16.0 km x h(-1) and the sit-and-reach test score (r = 0.68; p < 0.0001). These results suggest that the least flexible runners are also the most economical. It is possible that stiffer musculotendinous structures reduce the aerobic demand of submaximal running by facilitating a greater elastic energy return during the shortening phase of the stretch-shortening cycle.
Abstract.
Author URL.
Carter H, Jones AM, Maxwell NS, Doust JH (2002). The effect of interdian and diurnal variation on oxygen uptake kinetics during treadmill running.
J Sports Sci,
20(11), 901-909.
Abstract:
The effect of interdian and diurnal variation on oxygen uptake kinetics during treadmill running.
The aim of this study was to examine the variability of the oxygen uptake (VO2) kinetic response during moderate- and high-intensity treadmill exercise within the same day (at 06:00, 12:00 and 18:00 h) and across days (on five occasions). Nine participants (age 25 +/- 8 years, mass 70.2 +/- 4.7 kg, VO2max 4137 +/- 697 ml x min(-1); mean +/- s) took part in the study. Six of the participants performed replicate 'square-wave' rest-to-exercise transitions of 6 min duration at running speeds calculated to require 80% VO2 at the ventilatory threshold (moderate-intensity exercise) and 50% of the difference between VO2 at the ventilatory threshold and VO2max (50% delta; high-intensity exercise) on 5 different days. Although the amplitudes of the VO2 response were relatively constant (coefficient of variation approximately 6%) from day to day, the time-based parameters were more variable (coefficient of variation approximately 15 to 30%). All nine participants performed replicate square-waves for each time of day. There was no diurnal effect on the time-based parameters of VO2 kinetics during either moderate- or high-intensity exercise. However, for high-intensity exercise, the amplitude of the primary component was significantly lower during the 12:00 h trial (2859 +/- 142 ml x min(-1) vs 2955 +/- 135 ml x min(-1) at 06:00 h and 2937 +/- 137 ml x min(-1) at 18:00 h; P < 0.05), but this effect was eliminated when expressed relative to body mass. The results of this study indicate that the amplitudes of the VO2 kinetic responses to moderate- and high-intensity treadmill exercise are similar within and across test days. The time-based parameters, however, are more variable from day to day and multiple transitions are, therefore, recommended to increase confidence in the data.
Abstract.
Author URL.
Martin J, Smith NC, Tolfrey K, Jones AM (2001). Activity analysis of English Premiership rugby football union refereeing.
Ergonomics,
44(12), 1069-1075.
Abstract:
Activity analysis of English Premiership rugby football union refereeing.
Little is known about the physiological demands placed on officials during sporting activities. The purpose of this study was to ascertain the movement activities of referees during English Premiership rugby football union matches, and to determine the frequency and duration of these activities. Nine referees who were ranked in the top 20 referees in England were videotaped during a total of 19 matches. During playback of the videotapes, a single observer coded the referees' activities into one of six distinct categories (standing, walking forwards, walking backwards, jogging, running and sprinting) using a computerized video editing system (Observer Video-Pro). The referees were timed over a 20 m distance for the modes of locomotory activity, and the average velocity of the referee for each activity was used to calculate the total distance covered in each mode of activity during matches. The total distance covered during a match was (chi +/- SD) 8581 +/- 668 m. The mean percentage of total playing time spent in each activity was: standing still, 37.0 +/- 11.0%; walking forward, 29.5 +/- 7.2%; walking backward, 9.9 +/- 3.2%; jogging, 12.8 +/- 3.2%; running, 9.8 +/- 2.3%; and sprinting, 1.0 +/- 0.4%. There were a total of 672 transitions between modes of activity during a match. The results of this study suggest that refereeing top English rugby football union matches is physically demanding. Although the major physiological load is placed on the oxygen transport system, frequent sprint bouts and the associated requirements for acceleration and deceleration impose additional metabolic demands on referees. This information may be used in the design of physical training programmes to optimize performance in referees.
Abstract.
Author URL.
Burnley M, Doust JH, Carter H, Jones AM (2001). Effects of prior exercise and recovery duration on oxygen uptake kinetics during heavy exercise in humans.
Exp Physiol,
86(3), 417-425.
Abstract:
Effects of prior exercise and recovery duration on oxygen uptake kinetics during heavy exercise in humans.
Prior heavy exercise (above the lactate threshold, LT) reduces the amplitude of the pulmonary oxygen uptake (VO2) slow component during heavy exercise, yet the precise effect of prior heavy exercise on the phase II VO2 response remains to be established. This study was designed to test the hypotheses that (1) prior heavy exercise increases the amplitude of the phase II VO2 response independently of changes in the baseline VO2 value and (2) the effect of prior exercise depends on the amount of external work done during prior exercise, irrespective of the intensity of the prior exercise. Nine subjects performed two 6 min bouts of heavy cycling exercise separated by 6 min baseline pedalling recovery (A), two 6 min heavy exercise bouts separated by 12 min recovery (6 min rest and 6 min baseline pedalling, B), and a bout of moderate exercise (below the LT) in which the same amount of external work was performed as during the prior heavy exercise, followed by 6 min heavy exercise (C). In both tests a and B, prior heavy exercise significantly increased the absolute VO2 amplitude at the end of phase II (by approximately 150 ml x min(-1)), and reduced the amplitude of the VO2 slow component by a similar amount. Following 12 min of recovery (B), baseline VO2, but not blood [lactate], had returned to pre-exercise levels, indicating that these effects occurred independently of changes in baseline VO2. Prior moderate exercise (C) had no effect on either the VO2 or blood [lactate] responses to subsequent heavy exercise. The VO2 response to heavy exercise was therefore dependent on the intensity of prior exercise, and the effects on the amplitudes of the phase II and slow VO2 components persisted for at least 12 min following prior heavy exercise.
Abstract.
Author URL.
Jones AM, Burnley M, Carter H, Doust JH (2001). Interpreting VO2 kinetics in heavy exercise - Reply. J APPL PHYSIOL, 91(1), 531-532.
Hughson RL, MacDonald MJ, Tschakovsky ME, Jones AM, Burnley M, Carter H, Doust JH (2001). Interpreting V˙o 2 Kinetics in Heavy Exercise. Journal of Applied Physiology, 91(1), 530-532.
Williams CA, Carter H, Jones AM, Doust JH (2001). Oxygen uptake kinetics during treadmill running in boys and men.
J Appl Physiol (1985),
90(5), 1700-1706.
Abstract:
Oxygen uptake kinetics during treadmill running in boys and men.
The purpose of this study was to compare the kinetics of the oxygen uptake (VO(2)) response of boys to men during treadmill running using a three-phase exponential modeling procedure. Eight boys (11-12 yr) and eight men (21-36 yr) completed an incremental treadmill test to determine lactate threshold (LT) and maximum VO(2). Subsequently, the subjects exercised for 6 min at two different running speeds corresponding to 80% of VO(2) at LT (moderate exercise) and 50% of the difference between VO(2) at LT and maximum VO(2) (heavy exercise). For moderate exercise, the time constant for the primary response was not significantly different between boys [10.2 +/- 1.0 (SE) s] and men (14.7 +/- 2.8 s). The gain of the primary response was significantly greater in boys than men (239.1 +/- 7.5 vs. 167.7 +/- 5.4 ml. kg(-1). km(-1); P < 0.05). For heavy exercise, the VO(2) on-kinetics were significantly faster in boys than men (primary response time constant = 14.9 +/- 1.1 vs. 19.0 +/- 1.6 s; P < 0.05), and the primary gain was significantly greater in boys than men (209.8 +/- 4.3 vs. 167.2 +/- 4.6 ml. kg(-1). km(-1); P < 0.05). The amplitude of the VO(2) slow component was significantly smaller in boys than men (19 +/- 19 vs. 289 +/- 40 ml/min; P < 0.05). The VO(2) responses at the onset of moderate and heavy treadmill exercise are different between boys and men, with a tendency for boys to have faster on-kinetics and a greater initial increase in VO(2) for a given increase in running speed.
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Author URL.
Smith CG, Jones AM (2001). The relationship between critical velocity, maximal lactate steady-state velocity and lactate turnpoint velocity in runners.
Eur J Appl Physiol,
85(1-2), 19-26.
Abstract:
The relationship between critical velocity, maximal lactate steady-state velocity and lactate turnpoint velocity in runners.
In cycle exercise, it has been suggested that critical power, maximal lactate steady state, and lactate turnpoint all demarcate the transition between the heavy exercise domain (in which blood lactate is elevated above resting values but remains stable over time) and the very heavy exercise domain (in which blood lactate increases continuously throughout constant-intensity exercise). The purpose of the present study was to assess the level of agreement between critical velocity (CV), maximal lactate steady-state velocity (MLSSV), and lactate turnpoint velocity (LTPV) during treadmill running. Eight male subjects [mean (SD) age 28 (5) years, body mass 71.2 (8.0) kg, maximum oxygen uptake 54.9 (3.2) ml.kg(-1).min(-1)) performed an incremental treadmill test for the determination of LTPV (defined as a sudden and sustained increase in blood lactate concentration ([La]) at approximately equals 2.0-5.0 mM). The subjects returned to the laboratory on eight or nine occasions for the determination of CV and MLSSV. The CV was determined from four treadmill runs at velocities that were chosen to result in exhaustion within 2-12 min. The MLSSV was determined from four or five treadmill runs of up to 30 min duration and defined as the highest velocity at which blood [La] increased by no more than 1.0 mM after between 10 and 30 min of exercise. Analysis of variance revealed no significant differences between [mean (SD)] CV [14.4 (1.1) km.h(-1)], MLSSV [13.8 (1.1) km.h(-1)] and LTPV [13.7 (0.6) km.h(-1)]. However, the bias +/-95% limits of agreement for comparisons between CV and MLSSV [0.6 (2.2) km.h(-1)], CV and LTPV [0.7 (2.7) km.h(-1)], and MLSSV and LTPV [0.1 (1.8) km.h(-1)] suggest that the extent of disagreement is too great to allow one variable to be estimated accurately from another in individual subjects. Direct determination of MLSSV is necessary if precision is required in experimental studies.
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Author URL.
Carter H, Jones AM, Doust JH (2000). Changes in blood lactate and pyruvate concentrations and the lactate-to-pyruvate ratio during the lactate minimum speed test.
J Sports Sci,
18(3), 213-225.
Abstract:
Changes in blood lactate and pyruvate concentrations and the lactate-to-pyruvate ratio during the lactate minimum speed test.
The aim of this study was to assess the responses of blood lactate and pyruvate during the lactate minimum speed test. Ten participants (5 males, 5 females; mean +/- s: age 27.1+/-6.7 years, VO2max 52.0+/-7.9 ml x kg(-1) x min(-1)) completed: (1) the lactate minimum speed test, which involved supramaximal sprint exercise to invoke a metabolic acidosis before the completion of an incremental treadmill test (this results in a 'U-shaped' blood lactate profile with the lactate minimum speed being defined as the minimum point on the curve); (2) a standard incremental exercise test without prior sprint exercise for determination of the lactate threshold; and (3) the sprint exercise followed by a passive recovery. The lactate minimum speed (12.0+/-1.4 km x h(-1)) was significantly slower than running speed at the lactate threshold (12.4+/-1.7 km x h(-1)) (P < 0.05), but there were no significant differences in VO2, heart rate or blood lactate concentration between the lactate minimum speed and running speed at the lactate threshold. During the standard incremental test, blood lactate and the lactate-to-pyruvate ratio increased above baseline values at the same time, with pyruvate increasing above baseline at a higher running speed. The rate of lactate, but not pyruvate, disappearance was increased during exercising recovery (early stages of the lactate minimum speed incremental test) compared with passive recovery. This caused the lactate-to-pyruvate ratio to fall during the early stages of the lactate minimum speed test, to reach a minimum point at a running speed that coincided with the lactate minimum speed and that was similar to the point at which the lactate-to-pyruvate ratio increased above baseline in the standard incremental test. Although these results suggest that the mechanism for blood lactate accumulation at the lactate minimum speed and the lactate threshold may be the same, disruption to normal submaximal exercise metabolism as a result of the preceding sprint exercise, including a three- to five-fold elevation of plasma pyruvate concentration, makes it difficult to interpret the blood lactate response to the lactate minimum speed test. Caution should be exercised in the use of this test for the assessment of endurance capacity.
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Author URL.
Carter H, Jones AM, Barstow TJ, Burnley M, Williams CAP, Doust JH (2000). Effect of endurance training on oxygen uptake kinetics during treadmill running. Journal of Applied Physiology, 89, 1744-1752.
Carter H, Jones AM, Barstow TJ, Burnley M, Williams C, Doust JH (2000). Effect of endurance training on oxygen uptake kinetics during treadmill running.
J Appl Physiol (1985),
89(5), 1744-1752.
Abstract:
Effect of endurance training on oxygen uptake kinetics during treadmill running.
The purpose of this study was to examine the effect of endurance training on oxygen uptake (VO(2)) kinetics during moderate [below the lactate threshold (LT)] and heavy (above LT) treadmill running. Twenty-three healthy physical education students undertook 6 wk of endurance training that involved continuous and interval running training 3-5 days per week for 20-30 min per session. Before and after the training program, the subjects performed an incremental treadmill test to exhaustion for determination of the LT and the VO(2 max) and a series of 6-min square-wave transitions from rest to running speeds calculated to require 80% of the LT and 50% of the difference between LT and maximal VO(2). The training program caused small (3-4%) but significant increases in LT and maximal VO(2) (P
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Author URL.
Burnley M, Jones AM, Carter H, Doust JH (2000). Effects of prior heavy exercise on phase II pulmonary oxygen uptake kinetics during heavy exercise.
J Appl Physiol (1985),
89(4), 1387-1396.
Abstract:
Effects of prior heavy exercise on phase II pulmonary oxygen uptake kinetics during heavy exercise.
We tested the hypothesis that heavy-exercise phase II oxygen uptake (VO(2)) kinetics could be speeded by prior heavy exercise. Ten subjects performed four protocols involving 6-min exercise bouts on a cycle ergometer separated by 6 min of recovery: 1) moderate followed by moderate exercise; 2) moderate followed by heavy exercise; 3) heavy followed by moderate exercise; and 4) heavy followed by heavy exercise. The VO(2) responses were modeled using two (moderate exercise) or three (heavy exercise) independent exponential terms. Neither moderate- nor heavy-intensity exercise had an effect on the VO(2) kinetic response to subsequent moderate exercise. Although heavy-intensity exercise significantly reduced the mean response time in the second heavy exercise bout (from 65.2 +/- 4.1 to 47.0 +/- 3.1 s; P < 0.05), it had no significant effect on either the amplitude or the time constant (from 23.9 +/- 1.9 to 25.3 +/- 2.9 s) of the VO(2) response in phase II. Instead, this "speeding" was due to a significant reduction in the amplitude of the VO(2) slow component. These results suggest phase II VO(2) kinetics are not speeded by prior heavy exercise.
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Barstow TJ, Jones AM, Nguyen PH, Casaburi R (2000). Influence of muscle fibre type and fitness on the oxygen uptake/power output slope during incremental exercise in humans.
Exp Physiol,
85(1), 109-116.
Abstract:
Influence of muscle fibre type and fitness on the oxygen uptake/power output slope during incremental exercise in humans.
We recently reported that a higher percentage of type I fibres in vastus lateralis and a greater peak oxygen uptake (O2) were associated with a greater initial rise in O2 (O2 /W, where W is work rate) following the onset of heavy constant power output exercise (above the lactate threshold, LT). It was unclear if these results were true only for heavy exercise, or if the association between fibre type and/or fitness and O2 /W would also be seen for moderate (< LT) exercise. The purpose of the present study was to compare the relationships between fibre type or peak O2 and O2 /W determined for moderate (< LT) and heavy (> LT) exercise intensities during incremental exercise. Nine healthy subjects performed an incremental ramp test on a cycle ergometer. The O2 /Wslope was calculated for the domain of power outputs up to the LT (S1), from the LT towards peak O2 (S2), and over the entire linear portion of the O2 /W response (ST), and compared to fibre type distribution determined from biopsy of the vastus lateralis, and to peak O2 (as ml kg-1 min-1). Significant correlations between O2 /W and the proportion of type I fibres were found for each exercise domain (r is 0.69, 0.71 and 0.84 for S1, S2 and ST, respectively, P < 0.05). S1 ranged between about 9 ml min-1 W-1 for a low proportion of type I fibres and 11 ml min-1 W-1 for a high proportion of type I fibres. Similar correlations were also found between S2 (r = 0.70) and ST (r = 0.76) and peak O2. These results are consistent with our previous findings during > LT constant power output exercise, and suggest that the proportion of type I fibres, and possibly fitness as indicated by peak O2, is associated with greater O2 /W during the initial adjustment to < LT as well as > LT exercise. These results do not appear to be explained by classical descriptions of the kinetics of adjustment of O2 following the onset of ramp or constant power output exercise. They might reflect enhanced motor unit recruitment in subjects with a greater percentage of type I fibres, and/or who are more aerobically fit. However, the underlying mechanism for these findings must await further study.
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Pringle JSM, Carter H, Doust JH, Jones AM (2000). Oxygen uptake kinetics and electromyographic activity during level and graded treadmill running. J PHYSIOL-LONDON, 523, 243P-244P.
Carter H, Jones AM, Barstow TJ, Burnley M, Williams CA, Doust JH (2000). Oxygen uptake kinetics in treadmill running and cycle ergometry: a comparison.
J Appl Physiol (1985),
89(3), 899-907.
Abstract:
Oxygen uptake kinetics in treadmill running and cycle ergometry: a comparison.
The purpose of the present study was to comprehensively examine oxygen consumption (VO(2)) kinetics during running and cycling through mathematical modeling of the breath-by-breath gas exchange responses to moderate and heavy exercise. After determination of the lactate threshold (LT) and maximal oxygen consumption (VO(2 max)) in both cycling and running exercise, seven subjects (age 26.6 +/- 5.1 yr) completed a series of "square-wave" rest-to-exercise transitions at running speeds and cycling power outputs that corresponded to 80% LT and 25, 50, and 75%Delta (Delta being the difference between LT and VO(2 max)). VO(2) responses were fit with either a two- (LT) exponential model. The parameters of the VO(2) kinetic response were similar between exercise modes, except for the VO(2) slow component, which was significantly (P < 0.05) greater for cycling than for running at 50 and 75%Delta (334 +/- 183 and 430 +/- 159 ml/min vs. 205 +/- 84 and 302 +/- 154 ml/min, respectively). We speculate that the differences between the modes are related to the higher intramuscular tension development in heavy cycle exercise and the higher eccentric exercise component in running. This may cause a relatively greater recruitment of the less efficient type II muscle fibers in cycling.
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Author URL.
Jones AM, Pringle JSM, Martin JA (2000). Running economy is negatively related to lower limb flexibility in international male distance runners. Journal of Sports Sciences, 18(1), 33-34.
Tolfrey K, Jones AM, Campbell IG (2000). The effect of aerobic exercise training on the lipid-lipoprotein profile of children and adolescents.
Sports Med,
29(2), 99-112.
Abstract:
The effect of aerobic exercise training on the lipid-lipoprotein profile of children and adolescents.
Longitudinal paediatric population studies have provided evidence that the risk factor theory may be extended to children and adolescents. These studies could assist in identifying individuals at increased coronary risk. Numerous studies have focused on the effects of regular exercise on the paediatric lipoprotein profile, a recognised primary risk factor, with equivocal results. Cross-sectional comparisons of dichotomised groups provide the strongest evidence of an exercise effect. 'Trained' or 'active' children and adolescents demonstrate 'favourable' levels of high density lipoprotein-cholesterol (HDL-C), triacylglycerol, total cholesterol (TC)/HDL-C and low density lipoprotein-cholesterol (LDL-C)/HDL-C, whilst TC is generally unaffected. The evidence regarding LDL-C in these studies is equivocal. A possible self-selection bias means that a cause-effect relationship between exercise and the lipoprotein profile cannot be readily established from this design. Correlational studies are difficult to interpret because of differences in participant characteristics, methods employed to assess peak oxygen uptake and habitual physical activity (HPA), and the statistical techniques used to analyse multivariate data. Directly measured cardiorespiratory fitness does not appear to be related to lipoprotein profiles in the children and adolescents studied to date, although there are data to the contrary. The relationship with HPA is more difficult to decipher. The evidence suggests that a 'favourable' lipoprotein profile may be related to higher levels of HPA, although differences in assessment methods preclude a definitive answer. While few prospective studies exist, the majority of these longitudinal investigations suggest that imposed regular exercise has little, if any, influence on the lipoprotein levels of children and adolescents. However, most prospective studies have several serious methodological design weaknesses, including low sample size, inadequate exercise training volume and a lack of control individuals. Recent studies have suggested that increases in HDL-C and reductions in LDL-C may be possible with regular exercise. The identification of a dose-response relationship between exercise training and the lipoprotein profile during the paediatric years remains elusive.
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Author URL.
Jones AM, Carter H (2000). The effect of endurance training on parameters of aerobic fitness.
Sports Med,
29(6), 373-386.
Abstract:
The effect of endurance training on parameters of aerobic fitness.
Endurance exercise training results in profound adaptations of the cardiorespiratory and neuromuscular systems that enhance the delivery of oxygen from the atmosphere to the mitochondria and enable a tighter regulation of muscle metabolism. These adaptations effect an improvement in endurance performance that is manifest as a rightward shift in the 'velocity-time curve'. This shift enables athletes to exercise for longer at a given absolute exercise intensity, or to exercise at a higher exercise intensity for a given duration. There are 4 key parameters of aerobic fitness that affect the nature of the velocity-time curve that can be measured in the human athlete. These are the maximal oxygen uptake (VO2max), exercise economy, the lactate/ventilatory threshold and oxygen uptake kinetics. Other parameters that may help determine endurance performance, and that are related to the other 4 parameters, are the velocity at VO2max (V-VO2max) and the maximal lactate steady state or critical power. This review considers the effect of endurance training on the key parameters of aerobic (endurance) fitness and attempts to relate these changes to the adaptations seen in the body's physiological systems with training. The importance of improvements in the aerobic fitness parameters to the enhancement of endurance performance is highlighted, as are the training methods that may be considered optimal for facilitating such improvements.
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Author URL.
Burnley M, Carter H, Jones AM, Williams CA, Doust JH (2000). The effect of two different mathematical modelling procedures on the characterization of oxygen uptake kinetics during heavy exercise. Journal of Sports Sciences, 18(1), 28-29.
Burnley M, Carter H, Jones AM, Williams CA, Doust JH (2000). The effects of prior exercise on phase II pulmonary oxygen uptake kinetics and the slow component during heavy exercise in humans. Journal of Sports Sciences, 18(7).
Jones A (2000). Vo<inf>2</inf> slow component and performance in endurance sports [1]. British Journal of Sports Medicine, 34(6).
Jones AM, Carter H, Doust JH (1999). A disproportionate increase in VO2 coincident with lactate threshold during treadmill exercise.
Med Sci Sports Exerc,
31(9), 1299-1306.
Abstract:
A disproportionate increase in VO2 coincident with lactate threshold during treadmill exercise.
PURPOSE: the purpose of this study was to assess the relationship between pulmonary VO2 and running speed over a range of exercise intensities. During constant-load cycle exercise above the lactate threshold (Tlac), it has been shown that VO2 does not attain a steady state within 3 min but continues to rise until either a delayed but elevated steady-state VO2 is attained or exhaustion occurs. Since this greater oxygen cost of exercise (V02 slow component) has only been demonstrated at discrete exercise intensities above Tlac, it was hypothesised that the onset of the VO2 slow component would coincide with Tlac during an incremental test if the stage durations were of sufficient length. METHODS: Five male subjects (mean +/- SD age 31 +/- 2 yr: VO2peak 60.1 +/- 5.8 mL x kg(-1) x min(-1)) performed four identical treadmill tests within an 8-d period. The tests involved the completion of six stages of 7-min duration. Running speed was increased by 0.5 km x h(-1) between stages. In the first test, fingertip capillary blood was sampled at the end of each stage for determination of Tlac. For all tests expired air was collected into Douglas bags from 3.0 to 3.75 min and from 6.0 to 6.75 min of each stage to determine any increase in V02 (deltaVO2) over the duration of the stage. RESULTS: the mean deltaVO2 for each stage over the four tests was determined for each subject. Repeated measures ANOVA with post-hoc Tukey tests revealed a significant increase in deltaVO2 at running speeds above, but not below, Tlac. CONCLUSIONS: the results of this study confirm the close association between the VO2 slow component and the onset of lactic acidosis and demonstrate alinearity in the VO2-exercise intensity relationship above Tlac for incremental treadmill exercise.
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Carter H, Jones AM, Doust JH (1999). Effect of 6 weeks of endurance training on the lactate minimum speed.
J Sports Sci,
17(12), 957-967.
Abstract:
Effect of 6 weeks of endurance training on the lactate minimum speed.
The aim of this study was to assess the sensitivity of the lactate minimum speed test to changes in endurance fitness resulting from a 6 week training intervention. Sixteen participants (mean +/- s: age 23+/-4 years; body mass 69.7+/-9.1 kg) completed 6 weeks of endurance training. Another eight participants (age 23+/-4 years; body mass 72.7+/-12.5 kg) acted as non-training controls. Before and after the training intervention, all participants completed: (1) a standard multi-stage treadmill test for the assessment of VO2max, running speed at the lactate threshold and running speed at a reference blood lactate concentration of 3 mmol x l(-1); and (2) the lactate minimum speed test, which involved two supramaximal exercise bouts and an 8 min walking recovery period to increase blood lactate concentration before the completion of an incremental treadmill test. Additionally, a subgroup of eight participants from the training intervention completed a series of constant-speed runs for determination of running speed at the maximal lactate steady state. The test protocols were identical before and after the 6 week intervention. The control group showed no significant changes in VO2max, running speed at the lactate threshold, running speed at a blood lactate concentration of 3 mmol x l(-1) or the lactate minimum speed. In the training group, there was a significant increase in VO2max (from 47.9+/-8.4 to 52.2+/-2.7 ml x kg(-1) x min(-1)), running speed at the maximal lactate steady state (from 13.3+/-1.7 to 13.9+/-1.6 km x h(-1)), running speed at the lactate threshold (from 11.2+/-1.8 to 11.9+/-1.8 km x h(-1)) and running speed at a blood lactate concentration of 3 mmol x l(-1) (from 12.5+/-2.2 to 13.2+/-2.1 km x h(-1)) (all P < 0.05). Despite these clear improvements in aerobic fitness, there was no significant difference in lactate minimum speed after the training intervention (from 11.0+/-0.7 to 10.9+/-1.7 km x h(-1)). The results demonstrate that the lactate minimum speed, when assessed using the same exercise protocol before and after 6 weeks of aerobic exercise training, is not sensitive to changes in endurance capacity.
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Jones AM, McConnell AM (1999). Effect of exercise modality on oxygen uptake kinetics during heavy exercise.
Eur J Appl Physiol Occup Physiol,
80(3), 213-219.
Abstract:
Effect of exercise modality on oxygen uptake kinetics during heavy exercise.
The mechanisms responsible for the oxygen uptake (VO2) slow component during high-intensity exercise have yet to be established. In order to explore the possibility that the VO2 slow component is related to the muscle contraction regimen used, we examined the pulmonary VO2 kinetics during constant-load treadmill and cycle exercise at an exercise intensity that produced the same level of lactacidaemia for both exercise modes. Eight healthy subjects, aged 22-37 years, completed incremental exercise tests to exhaustion on both a cycle ergometer and a treadmill for the determination of the ventilatory threshold (defined as the lactate threshold, Th1a) and maximum VO2 (VO2max). Subsequently, the subjects completed two "square-wave" transitions from rest to a running speed or power output that required a VO2 that was halfway between the mode-specific Th1a and VO2max. Arterialised blood lactate concentration was determined immediately before and after each transition. The VO2 responses to the two transitions for each exercise mode were time-aligned and averaged. The increase in blood lactate concentration produced by the transitions was not significantly different between cycling [mean (SD) 5.9 (1.5) mM] and running [5.5 (1.6) mM]. The increase in VO2 between 3 and 6 min of exercise; (i.e. the slow component) was significantly greater in cycling than in running, both in absolute terms [290 (102) vs 200 (45) ml x min(-1); P
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Author URL.
Carter H, Jones AM, Doust JH (1999). Effect of incremental test protocol on the lactate minimum speed.
Med Sci Sports Exerc,
31(6), 837-845.
Abstract:
Effect of incremental test protocol on the lactate minimum speed.
PURPOSE: the purpose of this study was to investigate the effect of altering the initial running speed (RS) in the incremental portion of the lactate minimum test on the lactate minimum speed (LMS). METHODS: Eight well-trained endurance runners (mean +/- SD age 29.0 +/- 5.4 yr, body mass 72.0 +/- 5.6 kg, VO2max 63.1 +/- 3.8 mL x kg(-1) min(-1)) completed a standard incremental treadmill test for the assessment of the lactate threshold (LT) and VO2max, and eight lactate minimum tests. Following a period of supramaximal exercise, subjects were allowed 8 min of recovery to allow blood [lactate] to peak. Subjects then undertook eight randomly-assigned incremental treadmill tests from different initial running speeds (3.0, 2.5, 2.0, 1.5, 1.0, and 0.5 km x h(-1) below the predetermined RS-LT, at the RS-LT, and at 1.0 km x h(-1) above the RS-LT) with RS increased by 1.0 km x h(-1) every 5 min until volitional fatigue. Blood samples for the determination of blood [lactate] were taken at the end of each stage and the LMS was determined by fitting a spline function to the data. RESULTS: No LMS could be determined for the two highest initial RS conditions. For the other conditions, the LMS was significantly affected by the initial RS used in the incremental test and varied from 13.8 +/- 0.7 km x h(-1) with an initial RS of 3.0 km x h(-1) below the RS-LT, to 15.8 +/- 0.8 km x h(-1) with an initial RS of 0.5 km x h(-1) below the RS-LT. The LMS was significantly different from the RS-LT (15.4 +/- 0.8 km x h(-1)) (P < 0.05), except when the incremental test started at 1.0 or 1.5 km x h(-1) below the RS-LT. CONCLUSIONS: These results suggest that the LMS test is not a valid method for estimation of the LT since it is profoundly influenced by the starting speed selected for the incremental portion of the test.
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Author URL.
Tolfrey K, Campbell IG, Jones AM (1999). Intra-individual variation of plasma lipids and lipoproteins in prepubescent children.
Eur J Appl Physiol Occup Physiol,
79(5), 449-456.
Abstract:
Intra-individual variation of plasma lipids and lipoproteins in prepubescent children.
Estimates of the average intra-individual biological variability for plasma lipids and lipoproteins differs substantially among published studies. Moreover, this topic does not appear to have received consideration in exercise and health literature with normal, healthy children as subjects. The purpose of this study was, therefore, to determine the short-term, day-to-day variability of the lipid-lipoprotein profile from 19 children [mean (SD), 11.5 (0.8) years] from 3 separate venous blood samples. Intra-individual standard deviations, variances and coefficients of variance were determined for total cholesterol (TC), triacylglycerol (TG), high-density lipoprotein-cholesterol (HDL-C), HDL-C sub-fractions HDL2 and HDL3, and low-density lipoprotein-cholesterol (LDL-C). The intra-individual variation for TC and LDL-C was used to calculate the 95% confidence intervals (CIs) around the National Cholesterol Education Programme (NCEP 1991) cut-off points. The main finding was that all of the measured blood analytes including TC, TG, HDL-C, HDL2, HDL3, and LDL-C varied considerably from day-to-day. Coefficients of total variation ranged from 3.5% for HDL3 to 25.4% for TG. Classification of individuals using NCEP guidelines was difficult based on only one or two blood samples. The magnitude of variation for LDL-C meant that a 95% CI could not be constructed around the NCEP borderline-high classification from either one or two samples. However, averaging three TC and LDL-C measurements increased the likelihood of classification within the 95% CI. The results indicate that when using the NCEP guidelines for children and adolescents, true concentrations for TC and LDL-C should be based on the mean of multiple samples.
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Author URL.
Jones AM, Atter T, Georg KP (1999). Oral creatine supplementation improves multiple sprint performance in elite ice-hockey players.
J Sports Med Phys Fitness,
39(3), 189-196.
Abstract:
Oral creatine supplementation improves multiple sprint performance in elite ice-hockey players.
BACKGROUND: the purpose of this study was to assess the effect of oral creatine monohydrate supplementation on multiple sprint cycle and skating performance in ice-hockey players. PARTICIPANTS: sixteen elite ice-hockey players were selected as subjects. EXPERIMENTAL DESIGN: subjects were randomly assigned to either a creatine (Cr) (n = 8) or a placebo (P) group (n = 8) in a double blind design. After familiarization and baseline tests, subjects loaded with 5 g of creatine monohydrate or placebo (glucose) four times per day for 5 days, after which a maintenance dose of 5 g per day for 10 weeks was administered. At baseline, and after 10 days and 10 weeks of supplementation, subjects performed i) a cycle test involving 5 all-out sprints of 15 sec duration separated by 15 sec recovery with the resistance set at 0.075 body mass (kg), and ii) 6 timed 80-m skating sprints with the sprints initiated every 30 sec and a split time taken at 47 m. RESULTS: a two-way ANOVA demonstrated no significant change in any of the variables in the P group over the period of study. However, in the Cr group, average mean power output over the 5 sprints was significantly higher at 10 days (1074 +/- 241 W) and 10 weeks (1025 +/- 216 W) than at baseline (890 +/- 172 W), (p < 0.01). Average peak power output over the 5 sprints improved significantly from baseline (1294 +/- 311 W) to 10 days (1572 +/- 463 W), (p < 0.01). Average on-ice sprint performance to 47 m was significantly faster at 10 days (6.88 +/- 0.21 sec) and 10 weeks (6.96 +/- 0.19 sec) than at baseline (7.17 +/- 0.27 sec), (p < 0.005). CONCLUSIONS: This study demonstrates that creatine supplementation has an ergogenic effect in elite ice-hockey players.
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Tolfrey K, Campbell IG, Jones AM (1999). Selected predictor variables and the lipid-lipoprotein profile of prepubertal girls and boys.
Med Sci Sports Exerc,
31(11), 1550-1557.
Abstract:
Selected predictor variables and the lipid-lipoprotein profile of prepubertal girls and boys.
PURPOSE: it is still unclear how habitual physical activity (HPA), peak VO2, percent body fat (%BF), and dietary composition are related to the lipid-lipoprotein profile in children. The purpose of this study was to identify independent contributions from these selected predictor variables to prepubertal children's lipid-lipoprotein profile. METHODS: Peak VO2, HPA from continuous heart rate monitoring, %BF, 7-d dietary analysis, total cholesterol (TC), total triacylglycerol (TG), high density lipoprotein (HDL) cholesterol (HDL-C), low density lipoprotein (LDL) cholesterol (LDL-C), TC/HDL-C, and LDL-C/HDL-C were determined in 33 prepubertal girls and 38 prepubertal boys (mean +/- SD age, 10.6 +/- 0.7 yr). RESULTS: Bivariate correlation analyses revealed that peak VO2, %BF, and HPA were related to the lipid-lipoprotein profile in girls (P < 0.05). For the boys, HPA was only related to TC/HDL-C (P < 0.05) and LDL-C/HDL-C (P < 0.05), whereas daily energy intake (kJ x d(-1)) was associated with TC and LDL-C (P < 0.05). Multiple linear regression analyses indicated that peak VO2, %BF and HPA were the main predictor variables for the girls. Peak VO2 accounted for 22.7%, 24.8%, 22.5%, and 24.2% of the unique variance (sr(i)2) in TG, HDL-C, LDL-C/HDL-C, and TC/HDL-C, respectively. For TC and LDL-C in girls, sr(i)2 were 18.0% and 22.6%, respectively, from HPA. In contrast, only daily energy intake had a significant unique contribution to the variance of TC (15.4%) and LDL-C (22.0%) for the boys. SUMMARY: the main findings from this study were that the predictor variables are lipid-lipoprotein specific and depend on gender. These results would support the growing evidence that it is important to nurture an active lifestyle in children from an early age and that an awareness of fitness and body fatness is required.
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Jones AM (1998). A five year physiological case study of an Olympic runner.
Br J Sports Med,
32(1), 39-43.
Abstract:
A five year physiological case study of an Olympic runner.
OBJECTIVE: to study physiological changes caused by long term endurance training in a world class female distance runner, and to compare these changes with alterations in 3000 m running performance. METHODS: the subject underwent regular physiological assessment during the period 1991-1995. Physiological measures made included body composition, maximal oxygen uptake (VO2MAX), running economy, and lactate threshold. In addition, the running speed at VO2MAX was estimated. Test protocols, laboratory equipment, and laboratory techniques used were the same for each test session. RESULTS: the 3000 m race performance improved by 8% from 1991 to 1993 after which it stabilised. In contrast, VO2MAX fell from 1991 (73 ml/kg/min) to 1993 (66 ml/kg/min). Submaximal physiological variables such as lactate threshold (from 15.0 to 18.0 km/h) and running economy (from 53 ml/kg/min to 48 ml/kg/min at 16.0 km/h) improved over the course of the study. Despite no increase in VO2MAX, the reduction in the oxygen cost of submaximal running caused the estimated running speed at VO2MAX to increase from 19.0 km/h in 1991 to 20.4 km/h in 1995. CONCLUSIONS: Improvement in 3000 m running performance was not caused by an increase in VO2MAX. Rather, the extensive training programme adopted, together perhaps with physical maturation, resulted in improvements in submaximal fitness factors such as running economy and lactate threshold. These adaptations improved the running speed estimated to be associated with VO2MAX, and resulted in improved 3000 m running performance.
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Jones AM, Doust JH (1998). Assessment of the lactate and ventilatory thresholds by breathing frequency in runners.
J SPORT SCI,
16(7), 667-675.
Abstract:
Assessment of the lactate and ventilatory thresholds by breathing frequency in runners
The aim of this study was to establish the validity of the breakpoint in breathing frequency for the assessment of the lactate threshold and the ventilatory threshold during incremental running exercise. Twelve trained runners (mean +/- s: age 29 +/- 8 years; body mass 68.7 +/- 8.8 kg; VO2max 57.9 +/- 4.1 ml.kg(-1).min(-1)) performed randomly assigned incremental treadmill tests on separate days. In addition to the assessment of the VO2max (Test 1), the subjects performed two standard multi-stage treadmill tests (4-min stages) for the assessment of the lactate threshold while wearing (Test 2) and not wearing (Test 3) a standard mouthpiece and noseclip arrangement. Breathing frequency was measured by a thermistor, which was positioned in the back of the mouthpiece for Test 2, and fixed 3 cm in front of the mouth using a headband and flexible wiring for Test 3. All exercise tests were recorded on videotape and mean breathing frequency and stride rate were calculated for the last minute of each stage from real-time playback of the videotapes. The breathing frequency breakpoint was determined in six subjects only for Test 2 and in five subjects only for Test 3. For Test 2, there were no differences between the breakpoint in breathing frequency (14.7 +/- 0.9 km.h(-1)), the lactate threshold (14.7 +/- 0.9 km.h(-1)) and the ventilatory threshold (14.7 +/- 1.1 km.h(-1)). For Test 3, the breakpoint in breathing frequency (14.0 +/- 1.0 km.h(-1)) was not appreciably different from the lactate threshold (14.7 +/- 1.2 km.h(-1)). Hey plots showed marked interindividual differences in the responses of breathing frequency and tidal volume to exercise. In four subjects, the ventilatory threshold was mediated by a non-linear increase in tidal volume, with breathing frequency either increasing in a linear manner (n = 1) or remaining constant owing to entrainment of breathing frequency to cadence (n = 3). We conclude that the breakpoint in breathing frequency does not provide a valid method for the field-based assessment of the lactate or ventilatory thresholds in most subjects for running exercise.
Abstract.
Carter H, Doust J, Jones AM (1998). MECHANISM OF LACTATE ACCUMULATION DURING THE LACTATE MINIMUM' TEST. Medicine & Science in Sports & Exercise, 30(5).
Jones AM, Atter T, George KP (1998). ORAL CREATINE SUPPLEMENTATION IMPROVES MULTIPLE SPRINT PERFORMANCE IN ELITE ICE-HOCKEY PLAYERS. Medicine & Science in Sports & Exercise, 30(5).
Jones AM, Doust JH (1998). The relationship between the individual anaerobic threshold, the lactate threshold and the 4 mmol l<sup>-1</sup> blood lactate reference value during incremental treadmill exercise. Journal of Sports Sciences, 16(1).
Jones AM, Doust JH (1998). The validity of the lactate minimum test for determination of the maximal lactate steady state.
Med Sci Sports Exerc,
30(8), 1304-1313.
Abstract:
The validity of the lactate minimum test for determination of the maximal lactate steady state.
PURPOSE: the purpose of this study was to investigate the validity of the lactate minimum test ([Lac-]BMIN) in the determination of the velocity at the maximal lactate steady state (V-MLSS), and to identify those physiological factors most closely associated with 8-km running performance. METHODS: Thirteen trained male runners (VO2max range 53-67 mL.kg-1.min-1) took part in an 8-km simulated race on flat roads and completed a comprehensive battery of laboratory tests. RESULTS: Performance velocity was most strongly correlated with the estimated running velocity at VO2max (r = 0.93) and with V-MLSS (r = 0.92) and velocity at lactate threshold (V-Tlac) (r= 0.93). The running velocity at the ventilatory threshold (V-Tvent) (r = 0.81) and the [Lac-]BMIN (r = 0.83) also produced good correlations with performance velocity. Performance running velocity (mean +/- SEM 16.0 +/- 0.3 km.h-1) was not significantly different from V-MLSS (15.7 +/- 0.3 km.h-1). The running velocity at [Lac-]BMIN (14.9 +/- 0.2 km.h-1) was not significantly different from the V-Tlac (15.1 +/- 0.3 km.h-1) or V-Tvent (14.9 +/- 0.2 km.h-1) was not significantly different from the V-Tlac (15.1 +/- 0.3 km.h-1) or V-Tvent (14.9 +/- 0.3 km.h-1) but was significantly lower than the V-MLSS (P < 0.05). The [Lac-]BMIN provided the lowest correlation with V-MLSS (r = 0.61) and the worst estimate of V-MLSS (SEE = 0.75 km.h-1) compared with the other measures of lactate accumulation. The V-Tlac was not significantly different from V-MLSS and provided the highest correlation (r = 0.94) and a close estimate (SEE = 0.33 km.h-1) of the V-MLSS. CONCLUSIONS: it is concluded that of the measures studied relating to blood lactate accumulation during submaximal exercise, V-Tlac provides the best estimate of the V-MLSS and the V-Tlac had equal predictive power for 8-km race performance.
Abstract.
Author URL.
Jones AM, Doust JH (1997). The Conconi test in not valid for estimation of the lactate turnpoint in runners.
J Sports Sci,
15(4), 385-394.
Abstract:
The Conconi test in not valid for estimation of the lactate turnpoint in runners.
Conconi et al. (1982) reported that an observed deviation from linearity in the heart rate-running velocity relationship determined during a field test in runners coincided with the 'lactate threshold'. The aim of this study was to assess the validity of the original Conconi test using conventional incremental and constant-load laboratory protocols. Fourteen trained male distance runners (mean +/-s: age 22.6 +/- 3.4 years; body mass 67.6 +/- 4.8 kg; peak VO2 66.3 +/- 4.7 ml kg-1 min-1) performed a standard multi-stage test for determination of lactate turnpoint and a Conconi test on a motorized treadmill. A deviation from linearity in heart rate was observed in nine subjects. Significant differences were found to exist between running velocity at the lactate turnpoint (4.39 +/- 0.20 m s-1) and at deviation from linear heart rate (5.08 +/- 0.25 m s-1) (P < 0.01), and between heart rate at the lactate turnpoint (172 +/- 10 beats min-1) and at deviation from linearity (186 +/- 9 beats min-1) (P < 0.01). When deviation of heart rate from linearity was evident, it occurred at a systematically higher intensity than the lactate turnpoint and at approximately 95% of maximum heart rate. These results were confirmed by the physiological responses of seven subjects, who performed two constant-velocity treadmill runs at 0.14 m s-1 below the running velocity at the lactate turnpoint and that at which the heart rate deviated from linearity. For the lactate turnpoint trial, the prescribed 30 min exercise period was completed by all runners (terminal blood lactate concentration of 2.4 +/- 0.5 mM), while the duration attained in the trial for which heart rate deviated from linearity was 15.9 +/- 6.7 min (terminal blood lactate concentration of 8.1 +/- 1.8 mM). We concluded that the Conconi test is invalid for the non-invasive determination of the lactate turnpoint and that the deviation of heart rate from linearity represents the start of the plateau at maximal heart rate, the expression of which is dependent upon the specifics of the Conconi test protocol.
Abstract.
Author URL.
Jones AM, Doust JH (1996). A 1% treadmill grade most accurately reflects the energetic cost of outdoor running.
J Sports Sci,
14(4), 321-327.
Abstract:
A 1% treadmill grade most accurately reflects the energetic cost of outdoor running.
When running indoors on a treadmill, the lack of air resistance results in a lower energy cost compared with running outdoors at the same velocity. A slight incline of the treadmill gradient can be used to increase the energy cost in compensation. The aim of this study was to determine the treadmill gradient that most accurately reflects the energy cost of outdoor running. Nine trained male runners, thoroughly habituated to treadmill running, ran for 6 min at six different velocities (2.92, 3.33, 3.75, 4.17, 4.58 and 5.0 m s-1) with 6 min recovery between runs. This routine was repeated six times, five times on a treadmill set at different grades (0%, 0%, 1%, 2%, 3%) and once outdoors along a level road. Duplicate collections of expired air were taken during the final 2 min of each run to determine oxygen consumption. The repeatability of the methodology was confirmed by high correlations (r = 0.99) and non-significant differences between the duplicate expired air collections and between the repeated runs at 0% grade. The relationship between oxygen uptake (VO2) and velocity for each grade was highly linear (r > 0.99). At the two lowest velocities, VO2 during road running was not significantly different from treadmill running at 0% or 1% grade, but was significantly less than 2% and 3% grade. For 3.75 m s-1, the VO2 during road running was significantly different from treadmill running at 0%, 2% and 3% grades but not from 1% grade. For 4.17 and 4.58 m s-1, the VO2 during road running was not significantly different from that at 1% or 2% grade but was significantly greater than 0% grade and significantly less than 3% grade. At 5.0 m s-1, the VO2 for road running fell between the VO2 value for 1% and 2% grade treadmill running but was not significantly different from any of the treadmill grade conditions. This study demonstrates equality of the energetic cost of treadmill and outdoor running with the use of a 1% treadmill grade over a duration of approximately 5 min and at velocities between 2.92 and 5.0 m s-1.
Abstract.
Author URL.
Jones AM, Doust J (1996). A comparison of three protocols for the determination of maximal aerobic power in runners. Journal of Sports Sciences, 14(1).
Barstow TJ, Jones AM, Nguyen PH, Casaburi R (1996). Influence of muscle fiber type and pedal frequency on oxygen uptake kinetics of heavy exercise.
J Appl Physiol (1985),
81(4), 1642-1650.
Abstract:
Influence of muscle fiber type and pedal frequency on oxygen uptake kinetics of heavy exercise.
We tested the hypothesis that the amplitude of the additional slow component of O2 uptake (VO2) during heavy exercise is correlated with the percentage of type II (fast-twitch) fibers in the contracting muscles. Ten subjects performed transitions to a work rate calculated to require a VO2 equal to 50% between the estimated lactate (Lac) threshold and maximal VO2 (50% delta). Nine subjects consented to a muscle biopsy of the vastus lateralis. To enhance the influence of differences in fiber type among subjects, transitions were made while subjects were pedaling at 45, 60, 75, and 90 rpm in different trials. Baseline VO2 was designed to be similar at the different pedal rates by adjusting baseline work rate while the absolute increase in work rate above the baseline was the same. The VO2 response after the onset of exercise was described by a three-exponential model. The relative magnitude of the slow component at the end of 8-min exercise was significantly negatively correlated with % type I fibers at every pedal rate (r = 0.64 to 0.83, P < 0.05-0.01). Furthermore, the gain of the fast component for VO2 (as ml.min-1.W-1) was positively correlated with the % type I fibers across pedal rates (r = 0.69-0.83). Increase in pedal rate was associated with decreased relative stress of the exercise but did not affect the relationships between % fiber type and VO2 parameters. The relative contribution of the slow component was also significantly negatively correlated with maximal VO2 (r = -0.65), whereas the gain for the fast component was positively associated (r = 0.68-0.71 across rpm). The amplitude of the slow component was significantly correlated with net end-exercise Lac at all four pedal rates (r = 0.64-0.84), but Lac was not correlated with % type I (P > 0.05). We conclude that fiber type distribution significantly affects both the fast and slow components of VO2 during heavy exercise and that fiber type and fitness may have both codependent and independent influences on the metabolic and gas-exchange responses to heavy exercise.
Abstract.
Author URL.
Jones AM, Doust JH (1995). Lack of reliability in Conconi's heart rate deflection point.
Int J Sports Med,
16(8), 541-544.
Abstract:
Lack of reliability in Conconi's heart rate deflection point.
Conconi et al. (1982) reported the development of noninvasive field test for anaerobic threshold (AT) based upon an observed deviation from the linear heart rate (HR)--running velocity (RV) relationship at high RV (HRdev). While the validity of the Conconi test has been debated (Heck and Hollmann 1992; Tokmakidis and Leger 1992), the reliability of the Conconi test has never been independently assessed in athletes performing the protocol outlined by Conconi. This study evaluated the reliability of the Conconi test in 15 well-trained male distance runners (22.5 +/- 3.3 yrs, 67.7 +/- 4.8 kg, VO2 peak 66.4 +/- 4.8 ml.kg-1.min-1) who performed a treadmill simulation of the Conconi test protocol twice within a 4-8 day period. The results were as follows: 6 subjects demonstrated HRdev in both Conconi tests, 5 subjects demonstrated HRdev in only one test, and in 4 subjects HRdev could not be discerned in either test. It was concluded that failure to determine a reproducible HRdev by subjective assessment in 9 of 15 subjects makes the Conconi test unsuitable for reliable evaluation of AT.
Abstract.
Author URL.
Jones AM, Doust JH (1992). Conconi's heart rate deviation is an artefact of fixed distance protocol. Journal of Sports Sciences, 10(6).
