Journal articles
Cockcroft EJ, williams C, jackman S, armstrong N, barker A (In Press). Agreement and Reliability of Fasted and Oral Glucose Tolerance Test-Derived Indices of Insulin Sensitivity and Beta Cell Function in Boys. International journal of sports medicince
Williams C (In Press). Barriers and facilitators to physical activity among children, adolescents, and young adults with cystic fibrosis: a systematic review and thematic synthesis of qualitative of research. BMJ Open
Williams CAP, Vlachopoulos D, Ubago-Guisade E, Barker AR, Metcalf B, Fatouros IG, Avoniti A, Knapp K, Gracia-Marco L (In Press). Determinants of bone outcomes in adolescent athletes at baseline: the PRO-BONE study. Medicine and Science in Sports and Exercise
Gracia Marco L, Vlachopoulos D, Barker AR, Williams CA, Knapp K, Metcalf BS (In Press). Effect of a program of short bouts of exercise on bone health in adolescents involved in different sports: the PRO-BONE study protocol.
BMC Public HealthAbstract:
Effect of a program of short bouts of exercise on bone health in adolescents involved in different sports: the PRO-BONE study protocol
Background: Osteoporosis is a skeletal disease associated with high morbidity, mortality and increased economic costs. Early prevention during adolescence appears to be one of the most beneficial practices. Exercise is an effective approach for developing bone mass during puberty, but some sports may have a positive or negative impact on bone mass accrual. Plyometric jump training has been suggested as a type of exercise that can augment bone, but its effects on adolescent bone mass have not been rigorously assessed. The aims of the PRO-BONE study are to: 1) longitudinally assess bone health and its metabolism in adolescents engaged in osteogenic (football), non-osteogenic (cycling and swimming) sports and in a control group, and 2) examine the effect of a 9 month plyometric jump training programme on bone related outcomes in the sport groups.
Methods/Design: This study will recruit 105 males aged 12-14 years who have participated in sport specific training for at least 3 hours per week during the last 3 years in the following sports groups: football (n=30), cycling (n=30) and swimming (n=30). An age-matched control group (n=15) that does not engage in these sports more than 3 hours per week will also be recruited. Participants will be measured on 5 occasions: 1) at baseline; 2) after 12 months of sport specific training where each sport group will be randomly allocated into two sub-groups: intervention group (sport + plyometric jump training) and sport group (sport only); 3) exactly after the 9 months of intervention; 4) 6 months following the intervention; 5) 12 months following the intervention. Body composition (dual energy X-ray absorptiometry, air displacement plethysmography and bioelectrical impedance), bone stiffness index (ultrasounds), physical activity (accelerometers), diet (24 h recall questionnaire), pubertal maturation (Tanner stage), physical fitness (cardiorespiratory and muscular) and biochemical markers of bone formation and resorption will be measured at each visit.
Discussion: the PRO-BONE study is designed to investigate the impact of osteogenic and non-osteogenic sports on bone development in adolescent males during puberty, and how a plyometric jump training programme is associated with body composition parameters.
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Williams C, Oliveira R, Barker A, Kranen S, Debras F (In Press). Effects of high-intensity interval training on the vascular and autonomic components of the baroreflex at rest in adolescents. Pediatric Exercise Science
Denford S, Mackintosh KA, McNarry MA, Barker AR, Williams CA (In Press). Enhancing intrinsic motivation for physical activity among adolescents with cystic fibrosis: a qualitative study of the views of healthcare professionals. BMJ Open
Williams C (In Press). Experts unite to provide guidelines on exercise and physical activity in Cystic Fibrosis.
British Journal of Hospital MedicineAbstract:
Experts unite to provide guidelines on exercise and physical activity in Cystic Fibrosis
This editorial summarises a recently published, international and multidisciplinary, expert consensus statement about the important role of physical activity and exercise for people with cystic fibrosis (pwCF) – a genetic condition that currently affects ~11,000 people in the UK. This work from Williams et al. (2022) synthesises previous guidelines, clinical practice, and interpretation of evidence about the benefits of activity and exercise for patient health and management of illness.
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Chorlton R, Williams C, Denford S, Bond B (In Press). Incorporating movement breaks into primary school classrooms; a mixed methods approach to explore the perceptions of pupils, staff and Governors.
BMC Public HealthAbstract:
Incorporating movement breaks into primary school classrooms; a mixed methods approach to explore the perceptions of pupils, staff and Governors
Background: Public health guidelines for children advocate physical activity (PA) and the restriction of continuous sedentary time. Schools offer an attractive setting for health promotion, however school-based interventions to increase PA typically fail, and primary school children may spend most of the school day sitting down. Classroom movement breaks have been identified as an attractive opportunity to address this concern and may positively influence behaviour, but little is known about the barriers to implementing movement within lessons from a multi stakeholder perspective. The purpose of this study was to explore 1) the perceptions of primary school pupils, staff members and governors regarding classroom movement breaks, and 2) their perceived barriers and facilitators to implementing PA into the classroom. Methods: Thirty-four pupils (Key Stages 1 and 2, ages 5-7 y) took part in a focus group discussion. Sixty-four staff members and twenty governors completed a questionnaire and an optional follow up semi-structured telephone interview. Qualitative data were analysed using thematic analysis. Results: Pupils, staff members and governors expressed an enthusiasm for movement breaks provided that they were short, simple, pupil-guided and performed at the discretion of the teacher. Time and concerns regarding transitioning back to work following a movement break were identified as key barriers by pupils and staff. Governors and some staff expressed that favourable evidence for movement breaks is needed to facilitate their adoption, particularly regarding the potential for improvements in cognitive functioning or classroom behaviour. Conclusion: There is a wide appeal for classroom-based activity breaks, when delivered in a manner that is not disruptive. Future research which examines the potential benefits of such activity breaks is warranted.
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Tomlinson O, Barker A, Fulford J, Wilson P, Oades P, Williams C (In Press). Quantification of thigh muscle volume in children and adolescents using magnetic resonance imaging. European Journal of Sport Science, 20, 1215-1224.
Williams C, Breese B, Saynor Z, Barker A, Armstrong N (In Press). RELATIONSHIP BETWEEN (NON)LINEAR PHASE II PULMONARY OXYGEN UPTAKE KINETICS WITH SKELETAL MUSCLE OXYGENATION AND AGE IN 11 TO 15 Y OLDS. Experimental Physiology
Wilkinson K, Vlachopoulos D, Klentrou P, Ubago-Guisado E, de Moraes AC, Barker AR, Williams CA, Moreno LA, Gracia Marco L (In Press). Soft tissues, areal bone mineral density and hip geometry estimates in active young boys: the PRO-BONE study. European Journal of Applied Physiology
Williams C (In Press). Test-retest reliability of pulmonary oxygen uptake and muscle deoxygenation during moderate- and heavy-intensity cycling in youth elite-cyclists. Journal of Sports Sciences
Bond B, Hind S, Williams CA, Barker AR (In Press). The acute effect of exercise intensity on vascular function in adolescents.
Medicine and Science in Sports and ExerciseAbstract:
The acute effect of exercise intensity on vascular function in adolescents
Introduction: Impairments in vascular function are present in asymptomatic youths with risk factors for cardiovascular disease. Exercise can promote vascular health in youth, but the effect of exercise intensity and the time course in response to acute exercise are unknown. Methods: Twenty adolescents (10 male, 14.1 ± 0.3 y) on separate days, and in a counter-balanced order: 1) cycled at 90% of the gas exchange threshold (moderate-intensity exercise; MIE); 2) completed 8x1 min cycling at 90% peak power with 75 s recovery (high-intensity interval exercise; HIIE). The duration of MIE (25.8 ± 2.1 min) was work-matched to HIIE (23.0 min). Macro- and micro-vascular function were assessed before, immediately post, and 1 and 2 hours after exercise by flow mediated dilation (FMD) and laser Doppler imaging (total reactive hyperaemia). Results: FMD was attenuated immediately after HIIE (P
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Tomlinson O, Saynor Z, Stevens D, Urquhart D, Williams CA (In Press). The impact of Covid-19 upon the delivery of exercise services within cystic fibrosis clinics in the United Kingdom. Clinical Respiratory Journal
Williams C, Barker A, Wadey C, Weston M, Dorobantu D (In Press). The role of cardiopulmonary exercise testing (CPET) in predicting mortality and morbidity in people with congenital heart disease: a systematic review and meta-analysis. European Journal of Preventive Cardiology
Mann RH, McKay CD, Clift BC, Williams CA, Barker AR (In Press). Training Practices and Injuries in Competitive Adolescent Distance Runners: a Retrospective Cross-Sectional Study.
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Training Practices and Injuries in Competitive Adolescent Distance Runners: a Retrospective Cross-Sectional Study.
Abstract
. Background: Distance running is one of the most popular sports around the world. The epidemiology of running-related injuries (RRI) has been examined in adults, but only a few studies have focused on adolescent distance runners. Therefore, the purpose of this study was 1) to examine the training practices (frequency, volume, and intensity) and descriptive epidemiology of RRI (risks, rates, sites, and severity) in competitive adolescent distance runners (13-18 years) in England, and 2) to explore potential correlates (risk factors) of RRI. Methods: a cross-sectional study design was used. Adolescent distance runners (n = 113) were recruited from England Athletics affiliated athletics clubs. Participants voluntarily completed an online questionnaire between April and December 2018. At the point of completion, responses were based on the participant’s previous 12-months of distance running participation. Injury incidence proportions (IP) and incidence rates (IR) were calculated. Potential correlates of RRI were estimated using an odds ratio (OR) and 95% confidence intervals (CI). Results: the injury IP was 122/100 participants/year (95% CI: 113 to 138). The injury IR was 6.3/1000 participation hours (95% CI: 5.3 to 7.4). The most common injury sites were the knee, foot/toes, and lower leg; primarily caused by overuse. Exploratory univariate analyses showed a larger number of training sessions per week (volume) is associated with a lower risk of RRI (OR = 0.71, 95% CI: 0.53 to 0.94), and that a higher level of specialisation is associated with a lower risk of time loss injury (OR = 0.26, 95% CI: 0.11 to 0.63). Conclusions: Injury is common in adolescent distance runners, aligned with adult-based research. These data provide guidance for the development of appropriate injury prevention interventions.
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Denford S, Hill DM, Mackintosh KA, McNarry MA, Barker AR, Williams CA (In Press). Using photo-elicitation to explore perceptions of physical activity among young people with cystic fibrosis. BMC Pulmonary Medicine
Wargers A, Queral J, Mölenberg FJ, Tarro L, Elphick CM, Kalogerakou E, Karagiannis A, Llauradó E, Manios Y, Mavrogianni C, et al (2023). Citizen Science to improve healthy and active living among adolescents in four European countries: a protocol of the cluster randomised controlled trial of the Science Engagement to Empower aDolescentS (SEEDS) project.
BMJ Open,
13(5).
Abstract:
Citizen Science to improve healthy and active living among adolescents in four European countries: a protocol of the cluster randomised controlled trial of the Science Engagement to Empower aDolescentS (SEEDS) project.
INTRODUCTION: Improving healthy lifestyles of adolescents is challenging. Citizen Science is a way to engage them in the design and delivery of interventions, and may also increase their interest in science, technology, engineering and mathematics (STEM). The Science Engagement to Empower aDolescentS (SEEDS) project aims to use an equity-lens, and engage and empower boys and girls from deprived areas by designing and cocreating interventions to promote healthy lifestyles, and to seed interest in STEM. METHODS AND ANALYSIS: SEEDS is a cluster randomised controlled trial in four countries (Greece, the Netherlands, Spain and the UK). Each country will recruit six to eight high schools from lower socioeconomic neighbourhoods. Adolescents aged 13-15 years are the target population. High schools will be randomised into intervention or control group. Each country will select 15 adolescents from intervention schools called ambassadors, who will be involved throughout the project.In each country, focus groups with ambassadors and stakeholders will focus on physical activity, snacking behaviour and STEM. The input from focus groups will be used to shape Makeathon events, cocreation events where adolescents and stakeholders will develop the interventions. The resultant intervention will be implemented in the intervention schools during 6 months. In total, we aim to recruit 720 adolescents who will complete questionnaires related to healthy lifestyles and STEM outcomes at baseline (November 2021) and after the 6 months (June 2022). ETHICS AND DISSEMINATION: the four countries obtained approval from their corresponding Ethics Committees (Greece: Bioethics Committee of Harokopio University; the Netherlands: the Medical Research Ethics Committee of the Erasmus Medical Center; Spain: the Drug Research Ethics Committee of the Pere Virgili Health Research Institute; UK: Sport and Health Sciences Ethics Committee of the University of Exeter). Informed consent will be collected from adolescents and their parents in line with General Data Protection Regulation legislation. The findings will be disseminated by conference presentations, publications in scientific peer-reviewed journals and during (local) stakeholders and public events. Lessons learnt and the main results will also be used to provide policy recommendations. TRIAL REGISTRATION NUMBER: NCT05002049.
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Kelly AL, Williams CA, Jackson DT, Turnnidge J, Reeves MJ, Dugdale JH, Wilson MR (2023). Exploring the role of socioeconomic status and psychological characteristics on talent development in an English soccer academy.
Sci Med FootbAbstract:
Exploring the role of socioeconomic status and psychological characteristics on talent development in an English soccer academy.
Social factors and psychological characteristics can influence participation and development in talent pathways. However, the interaction between these two factors is relatively unknown. The aim of this study was to investigate the implications of socioeconomic status and psychological characteristics in English academy soccer players (n=58; aged 11 to 16 years). To assess socioeconomic status, participants' home postcodes were coded according to each individual's social classification and credit rating, applying the UK General Registrar Classification system and CameoTM geodemographic database, respectively. Participants also completed the six factor Psychological Characteristics for Developing Excellence Questionnaire (PCDEQ). A classification of 'higher-potentials' (n=19) and 'lower-potentials' (n=19) were applied through coach potential rankings. Data were standardised using z-scores to eliminate age bias and data were analysed using independent sample t-tests. Results showed that higher-potentials derived from families with significantly lower social classifications (p=0.014) and reported higher levels for PCDEQ Factor 3 (coping with performance and developmental pressures) (p=0.007) compared to lower-potentials. This study can be used to support the impetus for researchers and practitioners to consider the role of social factors and psychological characteristics when developing sporting talent. For example, facilitating player-centred development within an academy and, where necessary, providing individuals with additional support.
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sior JS, Zamunér AR, Madeyska M, Tomik A, Niszczota C, Williams CA, Werner B (2023). Heart Rate Variability in Individuals with Down Syndrome: a Scoping Review with Methodological Considerations.
International Journal of Environmental Research and Public Health,
20(2), 941-941.
Abstract:
Heart Rate Variability in Individuals with Down Syndrome: a Scoping Review with Methodological Considerations
Individuals with Down syndrome (DS) present similar heart rate variability (HRV) parameters at rest but different responses to selected movement maneuvers in comparison to individuals without DS, which indicates reduced vagal regulation. The present study undertakes a scoping review of research on HRV in individuals with DS, with special attention paid to the compliance of the studies with standards and methodological paper guidelines for HRV assessment and interpretation. A review was performed using PubMed, Web of Science and CINAHL databases to search for English language publications from 1996 to 2020 with the MESH terms “heart rate variability” and “down syndrome”, with the additional inclusion criteria of including only human participants and empirical investigations. From 74 studies, 15 were included in the review. None of the reviewed studies met the recommendations laid out by the standards and guidelines for providing the acquisition of RR intervals and necessary details on HRV analysis. Since authors publishing papers on this research topic do not adhere to the prescribed standards and guidelines when constructing the methodology, results of the research papers on the topic are not directly comparable. Authors need to design the study methodology more robustly by following the aforementioned standards, guidelines and recommendations.
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Riding NR, Dorobantu D-M, Williams CA, Stuart G, Fritsch P, Wilson MG, Mossialos E, Pieles G (2023). Protecting the stars of tomorrow: do international cardiovascular preparticipation screening policies account for the paediatric athlete? a systematic review and quality appraisal.
Br J Sports Med,
57(6), 371-380.
Abstract:
Protecting the stars of tomorrow: do international cardiovascular preparticipation screening policies account for the paediatric athlete? a systematic review and quality appraisal.
OBJECTIVE: (1) Identify and review current policies for the cardiovascular screening of athletes to assess their applicability to the paediatric population and (2) evaluate the quality of these policy documents using the Appraisal of Guidelines for Research & Evaluation II (AGREE II) tool. DESIGN: Systematic review and quality appraisal of policy documents. DATA SOURCES: a systematic search of PubMed, MEDLINE, Scopus, Web of Science, SportDiscus and CINAHL. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: an article was included if it was a policy/position statement/guideline/consensus or recommendation paper relating to athletes and cardiovascular preparticipation screening. RESULTS AND SUMMARY: of the 1630 articles screened, 13 met the inclusion criteria. Relevance to paediatric athletes was found to be high in 3 (23%), moderate in 6 (46%) and low in 4 (31%), and only 2 provide tailored guidance for the athlete aged 12-18 years. A median 5 related citations per policy investigated solely paediatric athletes, with study designs most commonly being retrospective (72%). AGREEII overall quality scores ranged from 25% to 92%, with a median of 75%. The lowest scoring domains were rigour of development; (median 32%) stakeholder involvement (median 47%) and Applicability (median 52%). CONCLUSION: Cardiac screening policies for athletes predominantly focus on adults, with few providing specific recommendations for paediatric athletes. The overall quality of the policies was moderate, with more recent documents scoring higher. Future research is needed in paediatric athletes to inform and develop cardiac screening guidelines, to improve the cardiac care of youth athletes.
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Tomlinson OW, Saynor ZL, Stevens D, Antoun J, Urquhart DS, Williams CA (2023). Survey of exercise testing and training in cystic fibrosis clinics in the UK: a decade of progress.
BMJ Open,
13(4), e072461-e072461.
Abstract:
Survey of exercise testing and training in cystic fibrosis clinics in the UK: a decade of progress
ObjectivesRegular exercise testing is recommended for people with cystic fibrosis (pwCF), as is the provision and regular review of exercise training programmes. A previous survey on exercise testing and training for pwCF in the UK was conducted over a decade ago. With the landscape of CF changing considerably during this time, this survey aimed to evaluate UK-based exercise testing and training practices for pwCF a decade on.DesignCross-sectional, online survey.ParticipantsA survey was distributed electronically to UK CF clinics and completed by the individual primarily responsible for exercise services. Descriptive statistics and qualitative analyses were undertaken.ResultsIn total, 31 CF centres participated, representing ~50% of UK specialist clinics. of these, 94% reported using exercise testing, 48% of which primarily use cardiopulmonary exercise testing. Exercise testing mostly occurs at annual review (93%) and is most often conducted by physiotherapists (62%). A wide variation in protocols, exercise modalities, normative reference values and cut-offs for exercise-induced desaturation are currently used. All centres reportedly discuss exercise training with pwCF; 94% at every clinic appointment. However, only 52% of centres reportedly use exercise testing to inform individualised exercise training. Physiotherapists typically lead discussions around exercise training (74%).ConclusionsThese data demonstrate that the majority of respondent centres in the UK now offer some exercise testing and training advice for pwCF, representing a marked improvement over the past decade. However, continued efforts are now needed to standardise exercise practices, particularly regarding field testing practices and the translation of test results into personalised training programmes for pwCF.
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Iniesta RR, Cook S, Oversby G, Koufaki P, Van der Linden ML, Vlachopoulos D, Williams CA, Urquhart DS (2023). Systematic review and meta-analysis: Associations of vitamin D with pulmonary function in children and young people with cystic fibrosis. Clinical Nutrition ESPEN, 54, 349-373.
Kranen SH, Oliveira RS, Bond B, Williams CA, Barker AR (2023). The effect of 4 weeks of highâintensity interval training and 2 weeks of detraining on cardiovascular disease risk factors in male adolescents. Experimental Physiology, 108(4), 595-606.
Dorobantu DM, Radulescu CR, Riding N, McClean G, de la Garza M-S, Abuli-Lluch M, Duarte N, Adamuz MC, Ryding D, Perry D, et al (2023). The use of 2-D speckle tracking echocardiography in assessing adolescent athletes with left ventricular hypertrabeculation meeting the criteria for left ventricular non-compaction cardiomyopathy.
Int J Cardiol,
371, 500-507.
Abstract:
The use of 2-D speckle tracking echocardiography in assessing adolescent athletes with left ventricular hypertrabeculation meeting the criteria for left ventricular non-compaction cardiomyopathy.
BACKGROUND: Current echocardiographic criteria cannot accurately differentiate exercise induced left ventricular (LV) hypertrabeculation in athletes from LV non-compaction cardiomyopathy (LVNC). This study aims to evaluate the role of speckle tracking echocardiography (STE) in characterising LV myocardial mechanics in healthy adolescent athletes with and without LVNC echocardiographic criteria. METHODS: Adolescent athletes evaluated at three sports academies between 2014 and 2019 were considered for this observational study. Those meeting the Jenni criteria for LVNC (end-systolic non-compacted/compacted myocardium ratio > 2 in any short axis segment) were considered LVNC+ and the rest LVNC-. Peak systolic LV longitudinal strain (Sl), circumferential strain (Sc), rotation (Rot), corresponding strain rates (SRl/c) and segmental values were calculated and compared using a non-inferiority approach. RESULTS: a total of 417 participants were included, mean age 14.5 ± 1.7 years, of which 6.5% were LVNC+ (n = 27). None of the athletes showed any additional LVNC clinical criteria. All average Sl, SRl Sc, SRc and Rot values were no worse in the LVNC+ group compared to LVNC- (p values range 0.0003-0.06), apart from apical SRc (p = 0.2). All 54 segmental measurements (Sl/Sc SRl/SRc and Rot) had numerically comparable means in both LVNC+ and LVNC-, of which 69% were also statistically non-inferior. CONCLUSIONS: Among healthy adolescent athletes, 6.5% met the echocardiographic criteria for LVNC, but showed normal LV STE parameters, in contrast to available data on paediatric LVNC describing abnormal myocardial function. STE could better characterise the myocardial mechanics of athletes with LV hypertrabeculation, thus allowing the transition from structural to functional LVNC diagnosis, especially in suspected physiological remodelling.
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Dorobantu DM, Riding N, McClean G, de la Garza M-S, Abuli-Lluch M, Sharma C, Duarte N, Adamuz MC, Watt V, Hamilton RM, et al (2023). The use of 2-D speckle tracking echocardiography in differentiating healthy adolescent athletes with right ventricular outflow tract dilation from patients with arrhythmogenic cardiomyopathy.
Int J Cardiol,
382, 98-105.
Abstract:
The use of 2-D speckle tracking echocardiography in differentiating healthy adolescent athletes with right ventricular outflow tract dilation from patients with arrhythmogenic cardiomyopathy.
AIMS: Echocardiographic assessment of adolescent athletes for arrhythmogenic cardiomyopathy (ACM) can be challenging owing to right ventricular (RV) exercise-related remodelling, particularly RV outflow tract (RVOT) dilation. The aim of this study is to evaluate the role of RV 2-D speckle tracking echocardiography (STE) in comparing healthy adolescent athletes with and without RVOT dilation to patients with ACM. METHODS AND RESULTS: a total of 391 adolescent athletes, mean age 14.5 ± 1.7 years, evaluated at three sports academies between 2014 and 2019 were included, and compared to previously reported ACM patients (n = 38 definite and n = 39 borderline). Peak systolic RV free wall (RVFW-Sl), global and segmental strain (Sl), and corresponding strain rates (SRl) were calculated. The participants meeting the major modified Task Force Criteria (mTFC) for RVOT dilation were defined as mTFC+ (n = 58, 14.8%), and the rest as mTFC- (n = 333, 85.2%). Mean RVFW-Sl was -27.6 ± 3.4% overall, -28.2 ± 4.1% in the mTFC+ group and - 27.5 ± 3.3% in the mTFC- group. mTFC+ athletes had normal RV-FW-Sl when compared to definite (-29% vs -19%, p
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Bianchim MS, McNarry MA, Holland A, Cox NS, Dreger J, Barker AR, Williams CA, Denford S, Mackintosh KA (2022). A Compositional Analysis of Physical Activity, Sedentary Time, and Sleep and Associated Health Outcomes in Children and Adults with Cystic Fibrosis.
International Journal of Environmental Research and Public Health,
19(9), 5155-5155.
Abstract:
A Compositional Analysis of Physical Activity, Sedentary Time, and Sleep and Associated Health Outcomes in Children and Adults with Cystic Fibrosis
This study sought to investigate the association of light physical activity (LPA), moderate-to-vigorous physical activity (MVPA), sedentary time (SED), and sleep with lung function in children and adults with CF. In total, 86 children (41 females; 13.6 ± 2.8 years; FEV1%predicted: 86 ± 1%) and 43 adults (21 females; 24.6 ± 4.7 years; FEV1%predicted: 63 ± 21%) with CF participated in this study. Wrist-worn accelerometery was used to assess PA, SED and sleep. Compositional linear regression models were conducted following normalisation via isometric log-ratio transformations. Sequential binary partitioning was applied to investigate the impact of reallocating 10 to 30 min between each behaviour on FEV1%predicted. A decline in FEV1%predicted was predicted with the reallocation of 30 min from MVPA to SED or LPA or sleep to any other behaviour in children (−3.04–−0.005%) and adults (−3.58–−0.005%). Conversely, improvements in FEV1%predicted were predicted when 30 min was reallocated to MVPA from LPA or SED in children (0.12–1.59%) and adults (0.77–2.10%), or when 30 min was reallocated to sleep from any other behaviour in both children (0.23–2.56%) and adults (1.08–3.58%). This study supports the importance of MVPA and sleep for maintaining and promoting lung function in people with CF.
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Williams C, Kelly A, Cook R, Jimenez Saiz SL, Wilson M (2022). A Multidisciplinary Investigation into the Talent Development Processes at an English Football Academy: a Machine Learning Approach.
Sports,
10Abstract:
A Multidisciplinary Investigation into the Talent Development Processes at an English Football Academy: a Machine Learning Approach
The talent development processes in youth football are both complex and multidimensional.
The purpose of this two-fold study was to apply a multidisciplinary, machine learning approach
to examine: (a) the developmental characteristics of under-9 to under-16 academy players (n = 98;
Study 1), and (b) the characteristics of selected and deselected under-18 academy players (n = 18;
Study 2). A combined total of 53 factors cumulated from eight data collection methods across two
seasons were analysed. A cross-validated Lasso regression was implemented, using the glmnet
package in R, to analyse the factors that contributed to: (a) player review ratings (Study 1), and
(b) achieving a professional contract (Study 2). Results showed non-zero coefficients for improvement
in subjective performance in 15 out of the 53 analysed features, with key findings revealing advanced
percentage of predicted adult height (0.196), greater lob pass (0.160) and average dribble completion
percentage (0.124), more total match-play hours (0.145), and an older relative age (BQ1 vs. BQ2:
ô0.133; BQ1 vs. BQ4: ô0.060) were the most important features that contributed towards player
review ratings. Moreover, PCDEQ Factor 3 and an ability to organise and engage in quality practice
(PCDEQ Factor 4) were important contributing factors towards achieving a professional contract.
Overall, it appears the key factors associated with positive developmental outcomes are not always
technical and tactical in nature, where coaches often have their expertise. Indeed, the relative
importance of these factors is likely to change over time, and with age, although psychological
attributes appear to be key to reaching potential across the academy journey. The methodological
techniques used here also serve as an impetus for researchers to adopt a machine learning approach
when analysing multidimensional databases.
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Johnson H, Duarte N, Ryding D, Perry D, McNally S, Stuart AG, Williams CA, Pieles G (2022). Assessment of a Novel, 22-lead Mobile Electrocardiogram in Elite, Adolescent Footballers.
Int J Sports Med,
43(3), 245-253.
Abstract:
Assessment of a Novel, 22-lead Mobile Electrocardiogram in Elite, Adolescent Footballers.
The 12-lead electrocardiogram is a key component of cardiac screening in elite adolescent footballers. Current technology hampers mobile electrocardiogram monitoring that could reduce the time-to-diagnosis in symptomatic athletes. Recently, a 22-lead mobile electrocardiogram monitor, CardioSecur (Personal MedSystems GmbH), has been approved for use in adults. In this study, the differences in parameter accuracy between CardioSecur's 22-lead electrocardiogram and the gold standard 12-lead electrocardiogram were assessed in elite adolescent footballers (n=31) using Bland-Altman and paired t-tests/Wilcoxon analysis. Agreement between the two devices was clinically acceptable for heart rate (bias=- 0.633 bpm), PR Interval (bias=- 1.73 ms), Bazzett's corrected QTc interval (bias=2.03 ms), T-wave axis (bias=6.55°), P-wave duration (bias=- 0.941 ms), Q-wave amplitude (bias=0.0195 mV), Q-wave duration (bias=1.98 ms), rhythm (bias=0.0333), ST-segment (bias=- 0.0629), J-point analysis (bias=- 0.01) and extended T wave and QRS duration analysis. Unsatisfactory agreement was observed in QRS axis (bias=- 19.4°), P-wave axis (bias=- 0.670°), QRS amplitude (bias=- 0.660 mV), P-wave amplitude (bias=0.0400 mV) and T-wave amplitude (bias=- 0.0675 mV). CardioSecur's 22-lead electrocardiogram agrees with the gold standard in rhythm, durations, T-wave determination in all leads assessed, permitting its use in adolescent footballers for immediate pitch- or track-side analysis.
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Bianchim MS, McNarry MA, Evans R, Thia L, Barker AR, Williams CA, Denford S, Mackintosh KA (2022). Calibration and Cross-validation of Accelerometry in Children and Adolescents with Cystic Fibrosis. Measurement in Physical Education and Exercise Science, 27(1), 51-59.
Caterini JE, Ratjen F, Barker AR, Williams CA, Rendall K, Schneiderman JE, Wells GD (2022). Exercise intolerance in cystic fibrosis-the role of CFTR modulator therapies.
Journal of Cystic Fibrosis,
21(2), 282-292.
Abstract:
Exercise intolerance in cystic fibrosis-the role of CFTR modulator therapies
Exercise intolerance is common in people with CF (pwCF), but not universal among all individuals. While associated with disease prognosis, exercise intolerance is not simply a reflection of the degree of lung disease. In people with severe CF, respiratory limitations may contribute more significantly to impaired exercise capacity than in those with mild-moderate CF. At all levels of disease severity, there are peripheral factors e.g. abnormal macro- and micro-vascular function that impair blood flow and reduce oxygen extraction, and mitochondrial defects that diminish metabolic efficiency. We discuss advances in understanding the central and peripheral mechanisms underlying exercise intolerance in pwCF. Exploring both the central and peripheral factors that contribute to exercise intolerance in CF can help inform the development of new therapeutic targets, as well as help define prognostic criteria.
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Tomlinson O, Williams CA (2022). Interpreting (and misclassifying) fitness – what do we really mean by ‘normal’?. The Sport and Exercise Scientist, 73, 20-21.
Sharma C, Dorobantu DM, Ryding D, Perry D, McNally SR, Stuart AG, Williams CA, Pieles GE (2022). Investigating the Accuracy of Quantitative Echocardiographic-Modified Task Force Criteria for Arrhythmogenic Ventricular Cardiomyopathy in Adolescent Male Elite Athletes.
Pediatr Cardiol,
43(2), 457-464.
Abstract:
Investigating the Accuracy of Quantitative Echocardiographic-Modified Task Force Criteria for Arrhythmogenic Ventricular Cardiomyopathy in Adolescent Male Elite Athletes.
Athlete preparticipation screening focuses on preventing sudden cardiac death (SCD) by detecting diseases such as arrhythmogenic ventricular cardiomyopathy (AVC), which affects primarily the right ventricular myocardium. Diagnosis may be obscured by physiological remodeling of the athlete heart. Healthy athletes may meet the 2010 Task Force Criteria right ventricular outflow tract (RVOT) dimension cut-offs, questioning the suitability of the modified Task Force Criteria (mTFC) in adolescent athletes. In this study, 67 male adolescent footballers undergoing preparticipation screening were reviewed. All athletes underwent a screening for resting ECG and echocardiogram according to the English FA protocol, as well as cardiopulmonary exercise testing, stress ECG, and exercise echocardiography. Athletes' right ventricular outflow tract (RVOT) that met the major AVC diagnostic criteria for dilatation were identified. of 67 evaluated athletes, 7 had RVOT dilatation that met the major criteria, all in the long axis parasternal view measurement. All had normal right ventricular systolic function, including normal free-wall longitudinal strain (ranging from - 21.5 to - 32.7%). Left ventricular ejection fraction ranged from 52 to 67%, without evidence of structural changes. Resting ECGs and cardiopulmonary exercise tests were normal in all individuals. In a series of healthy athletes meeting the major AVC diagnostic criteria for RVOT dilatation, none had any other pathological changes on a detailed screening including ECG, exercise testing, and echocardiography. This report highlights that current AVC echocardiographic diagnosis criteria have limitations in this population.
Abstract.
Author URL.
Evans DA, Jackson DT, Kelly AL, Williams CA, McAuley ABT, Knapman H, Morgan PT (2022). Monitoring Postmatch Fatigue During a Competitive Season in Elite Youth Soccer Players.
J Athl Train,
57(2), 184-190.
Abstract:
Monitoring Postmatch Fatigue During a Competitive Season in Elite Youth Soccer Players.
CONTEXT: Countermovement jump (CMJ) and perceived wellness measures are useful for monitoring fatigue. Fatigue indicators should simultaneously show sensitivity to previous load and demonstrate influence on subsequent physical output; however, these factors have not been examined. OBJECTIVE: to explore the efficacy of CMJ and wellness measures to both detect postmatch fatigue and predict subsequent physical match output in elite youth soccer players. DESIGN: Cross-sectional study. PATIENTS OR OTHER PARTICIPANTS: Sixteen soccer players (18 ± 1 years) from 36 English Football League Youth Alliance League fixtures. MAIN OUTCOME MEASURE(S): Physical match outputs (total distance, high-speed running, very high-speed running, and accelerations and decelerations [AD]) were recorded using a 10-Hz global positioning system and 200-Hz accelerometer device during competitive match play. The CMJ height and perceived wellness were assessed weekly and daily, respectively, as indirect indicators of fatigue. Four subunits of wellness (perceived soreness, energy, general stress, and sleep) were measured using customized psychometric questionnaires. RESULTS: Simple linear regression showed that match AD predicted energy (R2 = 0.08, P =. 001), stress (R2 = 0.09, P <. 001), and total wellness (R2 = 0.06, P =. 002) at 2 days postmatch. The CMJ (R2 = 0.05, P =. 002), stress (R2 = 0.08, P <. 001), sleep (R2 = 0.03, P =. 034), and total wellness (R2 = 0.05, P =. 006) measures at 5 days prematch predicted AD during the subsequent match. CONCLUSIONS: the CMJ and wellness measures may be useful for detecting postmatch fatigue. Wellness scores, but not CMJ, at 5 days prematch influenced subsequent match output and therefore may be used to plan and periodize training for the upcoming microcycle.
Abstract.
Author URL.
Caterini JE, Rendall K, Cifra B, Schneiderman JE, Ratjen F, Seed M, Rayner T, Weiss R, McCrindle BW, Noseworthy MD, et al (2022). Non-invasive MR imaging techniques for measuring femoral arterial flow in a pediatric and adolescent cohort.
Physiol Rep,
10(10).
Abstract:
Non-invasive MR imaging techniques for measuring femoral arterial flow in a pediatric and adolescent cohort.
Magnetic Resonance Imaging (MRI) is well-suited for imaging peripheral blood flow due to its non-invasive nature and excellent spatial resolution. Although MRI is routinely used in adults to assess physiological changes in chronic diseases, there are currently no MRI-based data quantifying arterial flow in pediatric or adolescent populations during exercise. Therefore the current research sought to document femoral arterial blood flow at rest and following exercise in a pediatric-adolescent population using phase contrast MRI, and to present test-retest reliability data for this method. Ten healthy children and adolescents (4 male; mean age 14.8 ± 2.4 years) completed bloodwork and resting and exercise MRI. Baseline images consisted of PC-MRI of the femoral artery at rest and following a 5 × 30 s of in-magnet exercise. To evaluate test-retest reliability, five participants returned for repeat testing. All participants successfully completed exercise testing in the MRI. Baseline flow demonstrated excellent reliability (ICC = 0.93, p = 0.006), and peak exercise and delta rest-peak flow demonstrated good reliability (peak exercise ICC = 0.89, p = 0.002, delta rest-peak ICC = 0.87, p = 0.003) between-visits. All three flow measurements demonstrated excellent reliability when assessed with coefficients of variance (CV's) (rest: CV = 6.2%; peak exercise: CV = 7.3%; delta rest-peak: CV = 7.1%). The mean bias was small for femoral arterial flow. There was no significant mean bias between femoral artery flow visits 1 and 2 at peak exercise. There were no correlations between age or height and any of the flow measurements. There were no significant differences between male and female participants for any of the flow measurements. The current study determined that peripheral arterial blood flow in children and adolescents can be evaluated using non-invasive phase contrast MRI. The MRI-based techniques that were used in the current study for measuring arterial flow in pediatric and adolescent patients demonstrated acceptable test-retest reliability both at rest and immediately post-exercise.
Abstract.
Author URL.
Tomlinson OW, Wadey CA, Williams CA (2022). Normal reference values for aerobic fitness in cystic fibrosis: a scoping review.
BMJ Open Sport & Exercise Medicine,
8(4), e001490-e001490.
Abstract:
Normal reference values for aerobic fitness in cystic fibrosis: a scoping review
ObjectiveThe importance of aerobic fitness (VO2peak) in cystic fibrosis (CF) is well established, and regular exercise testing is recommended. To standardise VO2peak, a ‘percentage of predicted’ (%pred) derived from normative reference values (NRV), as promoted by the 2015 European Cystic Fibrosis Society Exercise Working Group (ECFS EWG), can be reported. However, the NRVs used in CF and their relative frequency is unknown.MethodA scoping review was performed via systematic database searches (PubMed, Embase, Web of Science, SciELO, EBSCO) and forward citation searches for studies that include people with CF and report VO2peakas %pred. Studies were screened using Covidence, and data related to patient demographics, testing modality and reference equations were extracted. Additional analyses were performed on studies published in 2016–2021, following the ECFS EWG statement in 2015.ResultsA total of 170 studies were identified, dating from 1984 to 2022, representing 6831 patients with CF, citing 34 NRV. Most studies (154/170) used cycle ergometry, 15/170 used treadmills, and the remainder used alternative, combination or undeclared modalities. In total, 61/170 failed to declare the NRV used. There were 61 studies published since the ECFS EWG statement, whereby 18/61 used the suggested NRV.ConclusionThere is a wide discrepancy in NRV used in the CF literature base to describe VO2peakas %pred, with few studies using NRV from the ECFS EWG statement. This high variance compromises the interpretation and comparison of studies while leaving them susceptible to misinterpretation and limiting replication. Standardisation and alignment of reporting of VO2peakvalues are urgently needed.
Abstract.
Tomlinson OW, Kovalenko AG, Denford S, Van Beurden S, Cockcroft E, Williams CA (2022). P053 a novel family-focused intervention to support physical activity among children (6–12 years) with cystic fibrosis. Journal of Cystic Fibrosis, 21, S76-S76.
Kent T, Caunter A, Trott J, Williams CA, Enderby B, Withers NJ, Tomlinson OW (2022). P205 Kaftrio® improves VO2max in patients with cystic fibrosis. Journal of Cystic Fibrosis, 21, S123-S123.
Alkhraiji MH, Barker AR, Williams CA (2022). Reliability and validity of using the global school-based student health survey to assess 24 hour movement behaviours in adolescents from Saudi Arabia.
Journal of sports sciences,
40(14), 1578-1586.
Abstract:
Reliability and validity of using the global school-based student health survey to assess 24 hour movement behaviours in adolescents from Saudi Arabia.
This study aimed to examine the reliability and validity of Global School-based Student Health Survey (GSHS) to measure 24-hour movement behaviours (moderate-to-vigorous physical activity - MVPA; sedentary behaviour in the form of recreational screen time - ST; and sleep) in Saudi Arabian youths. A total of 120 (50% female) participants aged 12-15 years old were recruited from eight Saudi public middle schools. Participants completed GSHS survey twice and wore GENEActiv accelerometers for seven consecutive days and completed a diary log. ICC indicated moderate reliability in all 24-hour movement behaviours (ICC = 0.41 - 0.60), whereas ST and sleep were strongly reliable for females only (ICC = 0.61 - 0.80). Kappa agreements for all 24-hr movement behaviours were moderate (k = 0.41 - 0.60), but fair in MVPA and ST for males only (k = 0.21 - 0.40). Spearman's indicated low validity (r = 0.1 - 0.3) in MVPA and sleep between GSHS and GENEActiv. However, kappa test results indicated poor-to-slight agreements (k =
Abstract.
Wadey CA, Barker AR, Stuart G, Tran DL, Laohachai K, Ayer J, Cordina R, Williams CA (2022). Scaling Peak Oxygen Consumption for Body Size and Composition in People with a Fontan Circulation.
Journal of the American Heart Association,
11(24).
Abstract:
Scaling Peak Oxygen Consumption for Body Size and Composition in People with a Fontan Circulation
. Background
.
. Peak oxygen consumption (peak
.
.
.
.
. V
. Ì
.
.
. O
. 2
.
.
. $$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$
.
.
. ) is traditionally divided (“ratioâscaled”) by body mass (BM) for clinical interpretation. Yet, it is unknown whether ratioâscaling to BM can produce a valid sizeâindependent expression of peak
.
.
.
.
. V
. Ì
.
.
. O
. 2
.
.
. $$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$
.
.
. in people with a Fontan circulation. Furthermore, people with a Fontan circulation have deficits in lean mass, and it is unexplored whether using different measures of body composition may improve scaling validity. The objective was to assess the validity of different scaling denominators (BM, stature, body surface area, fatâfree mass, lean mass, and appendicular lean mass using ratio and allometric scaling).
.
.
.
. Methods and Results
.
. Eightyânine participants (age: 23.3±6.7 years; 53% female) with a Fontan circulation had their cardiorespiratory fitness and body composition measured by cardiopulmonary exercise testing and dualâenergy xâray absorptiometry. Ratio and allometric (logâlinear regression) scaling was performed and Pearson correlations assessed scaling validity. Scaling denominators BM (
. r
. =−0.25,
. P
. =0.02), stature (
. r
. =0.46,
. P
. <0.001), and body surface area (0.23,
. P
. =0.03) were significantly correlated with their respective ratioâscaled expressions of peak
.
.
.
.
. V
. Ì
.
.
. O
. 2
.
.
. $$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$
.
.
. but fatâfree mass, lean mass, or appendicular lean mass were not (
. r
. ≤0.11;
. R
. 2
. =1%). Allometrically expressed peak
.
.
.
.
. V
. Ì
.
.
. O
. 2
.
.
. $$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$
.
.
. resulted in no significant correlation with any scaling denominator (
. r
. =≤0.23;
. R
. 2
. =≤4%).
.
.
.
. Conclusions
.
. The traditional and accepted method of ratioâscaling to BM is invalid because it fails to create a sizeâindependent expression of peak
.
.
.
.
. V
. Ì
.
.
. O
. 2
.
.
. $$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$
.
.
. in people with a Fontan circulation. However, ratioâscaling to measures of body composition (fatâfree mass, lean mass, and appendicular lean mass) and allometric techniques can produce sizeâindependent expressions of peak
.
.
.
.
. V
. Ì
.
.
. O
. 2
.
.
. $$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$
.
.
. in people with a Fontan circulation.
.
.
Abstract.
Bianchim MS, McNarry MA, Barker AR, Williams CA, Denford S, Holland AE, Cox NS, Dreger J, Evans R, Thia L, et al (2022). Sleep, Sedentary Time and Physical Activity Levels in Children with Cystic Fibrosis.
International Journal of Environmental Research and Public Health,
19(12), 7133-7133.
Abstract:
Sleep, Sedentary Time and Physical Activity Levels in Children with Cystic Fibrosis
The aim of this study was to compare the use of generic and cystic fibrosis (CF)-specific cut-points to assess movement behaviours in children and adolescents with CF. Physical activity (PA) was assessed for seven consecutive days using a non-dominant wrist-worn ActiGraph GT9X in 71 children and adolescents (36 girls; 13.5 ± 2.9 years) with mild CF. CF-specific and generic Euclidean norm minus one (ENMO) cut-points were used to determine sedentary time (SED), sleep, light physical activity (LPA), moderate physical activity and vigorous physical activity. The effect of using a CF-specific or generic cut-point on the relationship between PA intensities and lung function was determined. Movement behaviours differed significantly according to the cut-point used, with the CF-specific cut-points resulting in less time asleep (−31.4 min; p < 0.01) and in LPA (−195.1 min; p < 0.001), and more SED and moderate-to-vigorous PA (159.3 and 67.1 min, respectively; both p < 0.0001) than the generic thresholds. Lung function was significantly associated with LPA according to the CF-specific cut-points (r = 0.52; p = 0.04). Thresholds developed for healthy populations misclassified PA levels, sleep and SED in children and adolescents with CF. This discrepancy affected the relationship between lung function and PA, which was only apparent when using the CF-specific cut-points. Promoting LPA seems a promising strategy to enhance lung function in children and adolescents with CF.
Abstract.
Tomlinson OW, Stoate ALE, Dobson L, Williams CA (2022). The Effect of Dysglycaemia on Changes in Pulmonary and Aerobic Function in Cystic Fibrosis.
Frontiers in Physiology,
13Abstract:
The Effect of Dysglycaemia on Changes in Pulmonary and Aerobic Function in Cystic Fibrosis
Cross-sectional studies have reported lower pulmonary and aerobic function during exercise in people with cystic fibrosis-related diabetes (CFRD) compared to non-CFRD counterparts. However, this association has yet to be longitudinally investigated. Therefore, this study examines these differences over time between people with cystic fibrosis (CF) of differing glycaemic status. Annual review data, including cardiopulmonary exercise tests and pulmonary function tests, were retrospectively analysed at baseline (T0, n = 82) and at a one-year follow-up (T1, n = 54). Data was analysed in three groups: normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and CFRD. Further analyses were undertaken, with a dichotomous split of NGT and a combined IGT/CFRD group. At baseline, a significant reduction in the majority of variables, including forced expiratory volume in one second (FEV1) and maximal oxygen uptake (VO2max), was observed in the CFRD (n = 19) group compared to NGT (n = 58). At follow-up, no significant differences were observed, and no interaction effect between CFRD status and time was identified. FEV1 and VO2max presented with varying directions and magnitudes of change within patients. In summary, patients with CFRD have a reduced aerobic and pulmonary function compared to non-CFRD counterparts, although such changes disappeared at follow up. Varying responses for FEV1 and VO2max highlight the need to consider both variables as independent markers of function in CF.
Abstract.
Williams CA, Barker AR, Denford S, van Beurden SB, Bianchim MS, Caterini JE, Cox NS, Mackintosh KA, McNarry MA, Rand S, et al (2022). The Exeter Activity Unlimited statement on physical activity and exercise for cystic fibrosis: methodology and results of an international, multidisciplinary, evidence-driven expert consensus.
Chron Respir Dis,
19Abstract:
The Exeter Activity Unlimited statement on physical activity and exercise for cystic fibrosis: methodology and results of an international, multidisciplinary, evidence-driven expert consensus.
BACKGROUND: the roles of physical activity (PA) and exercise within the management of cystic fibrosis (CF) are recognised by their inclusion in numerous standards of care and treatment guidelines. However, information is brief, and both PA and exercise as multi-faceted behaviours require extensive stakeholder input when developing and promoting such guidelines. METHOD: on 30th June and 1st July 2021, 39 stakeholders from 11 countries, including researchers, healthcare professionals and patients participated in a virtual conference to agree an evidence-based and informed expert consensus about PA and exercise for people with CF. This consensus presents the agreement across six themes: (i) patient and system centred outcomes, (ii) health benefits, iii) measurement, (iv) prescription, (v) clinical considerations, and (vi) future directions. The consensus was achieved by a stepwise process, involving: (i) written evidence-based synopses; (ii) peer critique of synopses; (iii) oral presentation to consensus group and peer challenge of revised synopses; and (iv) anonymous voting on final proposed synopses for adoption to the consensus statement. RESULTS: the final consensus document includes 24 statements which surpassed the consensus threshold (>80% agreement) out of 30 proposed statements. CONCLUSION: This consensus can be used to support health promotion by relevant stakeholders for people with CF.
Abstract.
Author URL.
Burley MJ, Blackwell J, Bond B, Williams C, Stephens FB (2022). The effect of various breathâhold techniques on the cardiorespiratory response to facial immersion in humans. Experimental Physiology, 108(1), 50-62.
Alrashidi M, Wadey CA, Tomlinson RJ, Buckingham G, Williams CA (2022). The efficacy of virtual reality interventions compared with conventional physiotherapy in improving the upper limb motor function of children with cerebral palsy: a systematic review of randomised controlled trials.
Disabil Rehabil, 1-11.
Abstract:
The efficacy of virtual reality interventions compared with conventional physiotherapy in improving the upper limb motor function of children with cerebral palsy: a systematic review of randomised controlled trials.
PURPOSE: Cerebral palsy (CP) is the commonest motor disability affecting children. This study reviewed the evidence for virtual reality (VR) intervention compared with conventional physiotherapy in upper limb function of children with CP. METHODS: Searches were undertaken in MEDLINE, EMBASE, PEDro, CENTRAL, Web of Science, CINAHL, ERIC, ICTRP, EU-CTR, ClinicalTrials.gov and EThOS databases. Only randomised-controlled trials (RCTs) were included. Two reviewers independently screened the search results, assessed full-text articles, extracted data and appraised the methodological quality by using the Cochrane collaboration's risk of bias (RoB2) tool. Albatross plots were used to synthesise the data. RESULTS: Seven RCTs, examining motor function in a total of 202 children with CP, included. Four trials used the Quality of Upper Extremity Skills Test (QUEST) as an outcome measure, and three trials used grip strength. These outcome measures were utilised to develop two Albatross plots. Data from the plots showed contradictory findings of the included studies. CONCLUSIONS: the effect of VR in the upper limb rehabilitation of children with CP remains unclear. All included studies used commercial non-immersive VR games. Future high-quality clinical research is needed to explore the extent to which non-immersive and immersive VR is feasible and effective with children and adolescents.IMPLICATIONS FOR REHABILITATIONThe current evidence supporting the use of VR as a rehabilitative tool is weak and uncertain.The current use of VR relies only on commercial non-immersive VR (off-shelf) games, which are not adjustable to meet the demands and goals of therapy programmes.Future research is needed to study the therapeutic feasibility of immersive VR with children and adolescents.
Abstract.
Author URL.
Dorobantu D, Riding N, Mcclean G, De La Garza MS, Luch MA, Adamuz C, Ryding D, Perry D, Mcnally S, Stuart A, et al (2022). The role of segmental speckle tracking echocardiography in characterising right ventricle dilation patterns: a multicentre study on healthy adolescent athletes. European Heart Journal - Cardiovascular Imaging, 23(Supplement_1).
Tomlinson OW, Markham L, Wollerton RL, Knight BA, Duckworth A, Gibbons MA, Scotton CJ, Williams CA (2022). Validity and repeatability of cardiopulmonary exercise testing in interstitial lung disease.
BMC Pulmonary Medicine,
22(1).
Abstract:
Validity and repeatability of cardiopulmonary exercise testing in interstitial lung disease
Abstract
. Background
. Cardiopulmonary exercise testing (CPET), and its primary outcome of peak oxygen uptake (VO2peak), are acknowledged as biomarkers in the diagnostic and prognostic management of interstitial lung disease (ILD). However, the validity and repeatability of CPET in those with ILD has yet to be fully characterised, and this study fills this evidence gap.
.
. Methods
. Twenty-six people with ILD were recruited, and 21 successfully completed three CPETs. of these, 17 completed two valid CPETs within a 3-month window, and 11 completed two valid CPETs within a 6-month window. Technical standards from the European Respiratory Society established validity, and repeatability was determined using mean change, intraclass correlation coefficient and typical error.
.
. Results
. Every participant (100%) who successfully exercised to volitional exhaustion produced a maximal, and therefore valid, CPET. Approximately 20% of participants presented with a plateau in VO2, the primary criteria for establishing a maximal effort. The majority of participants otherwise presented with secondary criteria of respiratory exchange ratios in excess of 1.05, and maximal heart rates in excess of their predicted values. Repeatability analyses identified that the typical error (expressed as percent of coefficient of variation) was 20% over 3-months in those reaching volitional exhaustion.
.
. Conclusion
. This work has, for the first time, fully characterised how patients with ILD respond to CPET in terms of primary and secondary verification criteria, and generated novel repeatability data that will prove useful in the assessment of disease progression, and future evaluation of therapeutic regimens where VO2peak is used as an outcome measure.
.
Abstract.
Tomlinson OW, Williams CA (2022). WS14.05 Normal fitness data in cystic fibrosis - a scoping review. Journal of Cystic Fibrosis, 21, S28-S28.
Morgan H, Tomlinson O, Williams C (2022). WS14.06 a retrospective, longitudinal analysis of pulmonary function and peak oxygen uptake in children and adults with cystic fibrosis. Journal of Cystic Fibrosis, 21, S28-S28.
Williams C (2022). Web-based physical activity promotion in young people with CF: a randomised controlled trial. Thorax, 1-8.
Tomlinson OW, Williams CA, Saynor ZL, Stevens D, Urquhart DS (2022). ePS2.10 Exercise testing and training in cystic fibrosis clinics in the United Kingdom: a 10-year update. Journal of Cystic Fibrosis, 21, S48-S49.
Dorobantu D, Radulescu C, Riding N, Mcclean G, Adamuz C, Ryding D, Perry D, Mcnally S, Stuart A, Oxborough D, et al (2021). Can left ventricular speckle tracking imaging be used in left ventricular non-compaction cardiomyopathy screening? a study of healthy paediatric athletes with and without echocardiographic criteria. European Heart Journal - Cardiovascular Imaging, 22(Supplement_1).
Dorobantu D, Riding N, Mcclean G, Adamuz C, Ryding D, Perry D, Mcnally S, Stuart A, Oxborough D, Willson M, et al (2021). Can right ventricular speckle tracking imaging be used in arrhytmogenic cardiomyopathy screening? a study of healthy paediatric athletes with and without echocardiographic modified task force criteria. European Heart Journal - Cardiovascular Imaging, 22(Supplement_1).
Pieles GE, Gowing L, Ryding D, Perry D, McNally SR, Stuart AG, Williams CA (2021). Characterisation of LV myocardial exercise function by 2-D strain deformation imaging in elite adolescent footballers.
European Journal of Applied Physiology,
121(1), 239-250.
Abstract:
Characterisation of LV myocardial exercise function by 2-D strain deformation imaging in elite adolescent footballers
Purpose: Few data exist on the descriptions of LV myocardial mechanics and reserve during dynamic exercise of adolescent athletes. The aim of this study was to describe the LV myocardial and cardiopulmonary changes during exercise using 2-D strain deformation imaging. Methods: Elite adolescent male football players (n = 42) completed simultaneous cardiopulmonary exercise testing (CPET) and exercise echocardiography measurement of LV myocardial deformation by 2-D strain imaging. LV longitudinal and circumferential 2-D strain and strain rates were analyzed at each stage during incremental exercise to a work rate of 150 W. Additionally, exercise LV myocardial deformation and its relation to metabolic exercise parameters were evaluated at each exercise stage and in recovery using repeated measures ANOVA, linear regression and paired t tests. Results: LV peak systolic baseline 2-D strain (longitudinal: − 15.4 ± 2.5%, circumferential: − 22.5 ± 3.1%) increased with each exercise stage, but longitudinal strain plateaued at 50 W (mean strain reserve − 7.8 ± 3.0) and did not significantly increase compared to subsequent exercise stages (P > 0.05), whilst circumferential strain (mean strain reserve − 11.6 ± 3.3) significantly increased (P < 0.05) throughout exercise up to 150 W as the dominant mechanism of exercise LV contractility increase. Regression analyses showed LV myocardial strain increased linearly relative to HR, VO2 and O2 pulse (P < 0.05) for circumferential deformation, but showed attenuation for longitudinal deformation. Conclusion: This study describes LV myocardial deformation dynamics by 2-D strain and provides reference values for LV myocardial strain and strain rate during exercise in adolescent footballers. It found important differences between LV longitudinal and circumferential myocardial mechanics during exercise and introduces a methodology that can be used to quantify LV function and cardiac reserve during exercise in adolescent athletes.
Abstract.
Williams C, Wadey C, Taylor R, Long L, Pieles G, Stuart G (2021). Cochrane corner: Physical activity interventions for people with congenital heart disease. Heart, 107, 447-449.
Amir NH, Dorobantu DM, Wadey CA, Caputo M, Stuart AG, Pieles GE, Williams CA (2021). Exercise training in paediatric congenital heart disease: fit for purpose?.
Archives of Disease in Childhood,
107(6), 525-534.
Abstract:
Exercise training in paediatric congenital heart disease: fit for purpose?
Exercise and physical activity (PA) have been shown to be effective, safe and feasible in both healthy children and children with congenital heart disease (CHD). However, implementing exercise training as an intervention is still not routine in children with CHD despite considerable evidence of health benefits and well-being. Understanding how children with CHD can safely participate in exercise can boost participation in PA and subsequently reduce inactivity-related diseases. Home-based exercise intervention, with the use of personal wearable activity trackers, and high-intensity interval training have been beneficial in adults’ cardiac rehabilitation programmes. However, these remain underutilised in paediatric care. Therefore, the aims of this narrative review were to synthesise prescribed exercise interventions in children with CHD, identify possible limitation to exercise training prescription and provide an overview on how to best integrate exercise intervention effectively for this population into daily practice.
Abstract.
Tomlinson O, Duckworth A, Markham L, Wollerton R, Knight B, Spiers A, Gibbons M, Williams C, Scotton C (2021). Feasibility of cardiopulmonary exercise testing in interstitial lung disease: the PETFIB study. BMJ Open Respiratory Research, 8
Mann RH, McKay CD, Clift BC, Williams CA, Barker AR (2021). Injuries and Training Practices in Competitive Adolescent Distance Runners: a Retrospective Cross-Sectional Study.
Frontiers in Sports and Active Living,
3Abstract:
Injuries and Training Practices in Competitive Adolescent Distance Runners: a Retrospective Cross-Sectional Study
Background: Distance running is one of the most popular sports around the world. The epidemiology of running-related injury (RRI) has been investigated in adults, but few studies have focused on adolescent distance runners.Objectives: (1) to provide descriptive epidemiology of RRI (risks, rates, body regions/areas, and severity) and examine the training practices (frequency, volume, and intensity) of competitive adolescent distance runners (13–18 years) in England, and (2) to describe potential risk factors of RRI.Methods: a cross-sectional study design was used. Adolescent distance runners (n = 113) were recruited from England Athletics affiliated clubs. Participants voluntarily completed an online questionnaire between April and December 2018. At the time of completion, responses were based on the participant's previous 12-months of distance running participation. Incidence proportions (IP) and incidence rates (IR) were calculated.Results: the IP for “all RRI” was 68% (95% CI: 60–77), while the IR was 6.3/1,000 participation hours (95% CI: 5.3–7.4). The most commonly injured body areas were the knee, foot/toes, and lower leg; primarily caused by overuse. The number of training sessions per week (i.e. frequency) significantly increased with chronological age, while a large proportion of participants (58%) self-reported a high level of specialisation.Conclusions: RRI is common in competitive adolescent distance runners. These descriptive data provide guidance for the development of RRI prevention measures. However, analytical epidemiology is required to provide better insight into potential RRI risk factors in this specific population.
Abstract.
Williams C, Alkhraiji M, Barker A (2021). Movement behaviors, cardiorespiratory fitness, and cardiovascular disease risk factors in children from the gulf cooperation council countries: a narrative review. Saudi Journal of Sports Medicine, 21(1), 7-7.
Tomlinson O, Stoate A, Dobson L, Williams C (2021). P197 Dysglycaemia and changes in aerobic function in cystic fibrosis. Journal of Cystic Fibrosis, 20
Mann RH, Clarsen BM, McKay CD, Clift BC, Williams CA, Barker AR (2021). Prevalence and burden of health problems in competitive adolescent distance runners: a 6-month prospective cohort study. Journal of Sports Sciences, 39(12), 1366-1375.
Dorobantu DM, Wadey CA, Amir NH, Stuart AG, Williams CA, Pieles GE (2021). The Role of Speckle Tracking Echocardiography in the Evaluation of Common Inherited Cardiomyopathies in Children and Adolescents: a Systematic Review.
Diagnostics,
11(4), 635-635.
Abstract:
The Role of Speckle Tracking Echocardiography in the Evaluation of Common Inherited Cardiomyopathies in Children and Adolescents: a Systematic Review
Speckle tracking echocardiography (STE) has gained importance in the evaluation of adult inherited cardiomyopathies, but its utility in children is not well characterized. We conducted a systematic review to evaluate the role of STE in pediatric inherited cardiomyopathies. PubMed, EMBASE, Web of Science, Scopus, CENTRAL and CINAHL databases were searched up to May 2020, for terms related to inherited cardiomyopathies and STE. Included were dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), left ventricular non-compaction (LVNC) and arrhythmogenic cardiomyopathy (ACM). A total of 14 cohorts were identified, of which six were in DCM, four in HCM, three in LVNC and one in ACM. The most commonly reported STE measurements were left ventricular longitudinal strain (Sl), circumferential strain (Sc), radial strain (Sr) and rotation/torsion/twist. Sl, Sc and were abnormal in all DCM and LVNC cohorts, but not in all HCM. Apical rotation and twist/torsion were increased in HCM, and decreased in LVNC. Abnormal STE parameters were reported even in cohorts with normal non-STE systolic/diastolic measurements. STE in childhood cardiomyopathies can detect early changes which may not be associated with changes in cardiac function detectable by non-STE methods. Longitudinal and circumferential strain should be introduced in the cardiomyopathy echocardiography protocol, reflecting current practice in adults.
Abstract.
Kranen SH, Oliveira RS, Bond B, Williams CA, Barker AR (2021). The acute effect of highâ and moderateâintensity interval exercise on vascular function before and after a glucose challenge in adolescents. Experimental Physiology, 106(4), 913-924.
Tomlinson OW, Denford S, Barker AR, Schneiderman JE, Campisi ES, Douglas H, Rand S, McNarry MA, Mackintosh KA, Williams CA, et al (2021). The impact of physical activity and exercise interventions for physical health in people with cystic fibrosis: protocol for a systematic review.
Systematic Reviews,
10(1).
Abstract:
The impact of physical activity and exercise interventions for physical health in people with cystic fibrosis: protocol for a systematic review
Abstract
. Background
. Cystic fibrosis (CF) is a genetically inherited, life-limiting condition, affecting ~90,000 people globally. Physical activity (PA) and exercise form an integral component of CF management, and have been highlighted by the CF community as an area of interest for future research. Previous reviews have solely focused on PA or structured exercise regimens independent of one another, and thus a comprehensive assessment of the physical health benefits of all PA, including exercise, interventions, is subsequently warranted. Therefore, the purpose of this review is to evaluate the effects of both PA and exercise upon outcomes of physical health and healthcare utilisation in people with CF.
.
. Methods
. A systematic review has been registered and reported in line with Preferred Reporting Items for Systematic Reviews and Meta-Analysis-P guidelines. This will include randomised control trials on the effects of PA and exercise, relative to usual treatment, upon people with CF. Primary outcomes will include variables associated with fitness, PA, lung health, inflammation, body composition, glycaemic control and patient-reported outcomes. Secondary outcomes will include adverse events and healthcare utilisation. Searches will be undertaken in Ovid MEDLINE, OVID EMBASE, PsychINFO, ERIC, SPORTDiscus, ASSIA, CCTR, CINHAL and Web of Science databases, and will be searched from date of inception onwards. Two reviewers will independently screen citations and abstracts, and full-texts, for inclusion and data extraction, respectively. Methodological quality will be assessed using the Cochrane Risk of Bias-2 tool. If feasible, random-effects meta-analyses will be conducted where appropriate. Additional analyses will explore potential sources of heterogeneity, such as age, sex, and disease severity.
.
. Discussion
. This systematic review will build on previous research, by comprehensively assessing the impact of both PA and exercise upon physical health and healthcare utilisation in people with CF. Results of this review will be utilised to inform discussions that will ultimately result in a consensus document on the impact of physical activity and exercise for people with CF.
.
. Systematic review registration
. PROSPERO CRD42020184411
.
Abstract.
Mann R, Barker A, Williams C, Clift B (2020). 307 the prevalence and burden of health problems in competitive adolescent distance runners: a prospective study in England. British Journal of Sports Medicine, 54(Suppl 1).
Kelly A, Wilson MR, Jackson DT, Goldman DE, Turnnidge J, CĂŽtĂ© J, Williams CA (2020). A multidisciplinary investigation into “playing-up” in academy football according to age phase. Journal of Sports Sciences, 39(8), 854-864.
Mandalia V, Williams C, Kosy J, Brown K, Schranz P, Redfern A, Silver D, Powell R (2020). Bone Marrow Oedema in the Knees of Asymptomatic High-Level Athletes: Prevalence and Associated Factors.
Indian Journal of Orthopaedics,
54(3), 324-331.
Abstract:
Bone Marrow Oedema in the Knees of Asymptomatic High-Level Athletes: Prevalence and Associated Factors
Background: Bone marrow oedema (BMO), seen on magnetic resonance imaging, can be associated with various injuries to the knee but may also occur in asymptomatic athletes. The prevalence and causal factors for these observations are not well understood. The aim of this study was to determine the prevalence of BMO in asymptomatic knees of athletes, competing at a high level, and to investigate the associated factors. Materials and Methods: Twenty-five asymptomatic university athletes, competing at regional to international level, were recruited. Bilateral knee magnetic resonance imaging was performed in each athlete (total 50 knee scans) at the end of their competitive season. Imaging studies were reported independently by two experienced consultant musculoskeletal radiologists. Results: There was almost perfect agreement between reporters for diagnosis of BMO (κ = 0.896). Seven participants (28%) were found to have BMO (six in one knee and one bilaterally). The amount of time spent training, during the season, was significantly associated with the appearance of BMO (p < 0.05). Conclusion: the occurrence of BMO in asymptomatic knees of athletes is common (occurring in over one-quarter of knees) and may be associated with training intensity. This should be considered when treating athletes and deciding upon appropriate treatment plans.
Abstract.
Bianchim MS, McNarry MA, Larun L, Barker AR, Williams CA, Mackintosh KA (2020). Calibration and validation of accelerometry using cut-points to assess physical activity in paediatric clinical groups: a systematic review. Preventive Medicine Reports, 19, 101142-101142.
Tomlinson O, Trott J, Williams C, Withers N, Oades P (2020). Challenges in Implementing Routine Cardiopulmonary Exercise Testing in Cystic Fibrosis Clinical Practice: a Single-Centre Review. SN Comprehensive Clinical Medicine, 2, 327-331.
GÄ
sior JS, Zamunér AR, Silva LEV, Williams CA, Baranowski R, Sacha J, Machura P, Kochman W, Werner B (2020). Heart Rate Variability in Children and Adolescents with Cerebral Palsy-A Systematic Literature Review.
J Clin Med,
9(4).
Abstract:
Heart Rate Variability in Children and Adolescents with Cerebral Palsy-A Systematic Literature Review.
Cardiac autonomic dysfunction has been reported in patients with cerebral palsy (CP). The aim of this study was to assess the existing literature on heart rate variability (HRV) in pediatric patients with CP and a special attention was paid to the compliance of the studies with the current HRV assessment and interpretation guidelines. A systematic review was performed in PubMed, Web of Science, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases searched for English language publications from 1996 to 2019 using Medical Subject Headings (MeSH) terms "heart rate variability" and "cerebral palsy" in conjunction with additional inclusion criteria: studies limited to humans in the age range of 0-18 years and empirical investigations. Out of 47 studies, 12 were included in the review. Pediatric patients with CP presented a significantly higher resting heart rate and reduced HRV, different autonomic responses to movement stimuli compared to children with normal development, but also reduced HRV parameters in the children dependent on adult assistance for mobility compared to those generally independent. None of the included studies contained the necessary details concerning RR intervals acquisition and HRV measurements as recommended by the guidelines. Authors of HRV studies should follow the methodological guidelines and recommendations on HRV measurement, because such an approach may allow a direct comparison of their results.
Abstract.
Author URL.
Malik AA, Williams CA, Weston KL, Barker AR (2020). Influence of personality and self-efficacy on perceptual responses during high-intensity interval exercise in adolescents. Journal of Applied Sport Psychology, 33(6), 590-608.
Kelly AL, Williams CA (2020). Physical Characteristics and the Talent Identification and Development Processes in Male Youth Soccer: a Narrative Review. Strength & Conditioning Journal, 42(6), 15-34.
Williams C, Denford S, Tomlinson O, Barker A, McNarry M, Mackintosh K, Cox N, Holland A, O'Halloran P (2020). Physical activity for cystic fibrosis: perceptions of people with cystic fibrosis, parents and healthcare professionals. ERJ Open Research, 6
Williams CA, Wadey C, Pieles G, Stuart G, Taylor RS, Long L (2020). Physical activity interventions for people with congenital heart disease.
Cochrane Database Syst Rev,
10(10).
Abstract:
Physical activity interventions for people with congenital heart disease.
BACKGROUND: Congenital heart disease (ConHD) affects approximately 1% of all live births. People with ConHD are living longer due to improved medical intervention and are at risk of developing non-communicable diseases. Cardiorespiratory fitness (CRF) is reduced in people with ConHD, who deteriorate faster compared to healthy people. CRF is known to be prognostic of future mortality and morbidity: it is therefore important to assess the evidence base on physical activity interventions in this population to inform decision making. OBJECTIVES: to assess the effectiveness and safety of all types of physical activity interventions versus standard care in individuals with congenital heart disease. SEARCH METHODS: We undertook a systematic search on 23 September 2019 of the following databases: CENTRAL, MEDLINE, Embase, CINAHL, AMED, BIOSIS Citation Index, Web of Science Core Collection, LILACS and DARE. We also searched ClinicalTrials.gov and we reviewed the reference lists of relevant systematic reviews. SELECTION CRITERIA: We included randomised controlled trials (RCT) that compared any type of physical activity intervention against a 'no physical activity' (usual care) control. We included all individuals with a diagnosis of congenital heart disease, regardless of age or previous medical interventions. DATA COLLECTION AND ANALYSIS: Two review authors (CAW and CW) independently screened all the identified references for inclusion. We retrieved and read all full papers; and we contacted study authors if we needed any further information. The same two independent reviewers who extracted the data then processed the included papers, assessed their risk of bias using RoB 2 and assessed the certainty of the evidence using the GRADE approach. The primary outcomes were: maximal cardiorespiratory fitness (CRF) assessed by peak oxygen consumption; health-related quality of life (HRQoL) determined by a validated questionnaire; and device-worn 'objective' measures of physical activity. MAIN RESULTS: We included 15 RCTs with 924 participants in the review. The median intervention length/follow-up length was 12 weeks (12 to 26 interquartile range (IQR)). There were five RCTs of children and adolescents (n = 500) and 10 adult RCTs (n = 424). We identified three types of intervention: physical activity promotion; exercise training; and inspiratory muscle training. We assessed the risk of bias of results for CRF as either being of some concern (n = 12) or at a high risk of bias (n = 2), due to a failure to blind intervention staff. One study did not report this outcome. Using the GRADE method, we assessed the certainty of evidence as moderate to very low across measured outcomes. When we pooled all types of interventions (physical activity promotion, exercise training and inspiratory muscle training), compared to a 'no exercise' control CRF may slightly increase, with a mean difference (MD) of 1.89 mL/kg-1/min-1 (95% CI -0.22 to 3.99; n = 732; moderate-certainty evidence). The evidence is very uncertain about the effect of physical activity and exercise interventions on HRQoL. There was a standardised mean difference (SMD) of 0.76 (95% CI -0.13 to 1.65; n = 163; very low certainty evidence) in HRQoL. However, we could pool only three studies in a meta-analysis, due to different ways of reporting. Only one study out of eight showed a positive effect on HRQoL. There may be a small improvement in mean daily physical activity (PA) (SMD 0.38, 95% CI -0.15 to 0.92; n = 328; low-certainty evidence), which equates to approximately an additional 10 minutes of physical activity daily (95% CI -2.50 to 22.20). Physical activity and exercise interventions likely result in an increase in submaximal cardiorespiratory fitness (MD 2.05, 95% CI 0.05 to 4.05; n = 179; moderate-certainty evidence). Physical activity and exercise interventions likely increase muscular strength (MD 17.13, 95% CI 3.45 to 30.81; n = 18; moderate-certainty evidence). Eleven studies (n = 501) reported on the outcome of adverse events (73% of total studies). of the 11 studies, six studies reported zero adverse events. Five studies reported a total of 11 adverse events; 36% of adverse events were cardiac related (n = 4); there were, however, no serious adverse events related to the interventions or reported fatalities (moderate-certainty evidence). No studies reported hospital admissions. AUTHORS' CONCLUSIONS: This review summarises the latest evidence on CRF, HRQoL and PA. Although there were only small improvements in CRF and PA, and small to no improvements in HRQoL, there were no reported serious adverse events related to the interventions. Although these data are promising, there is currently insufficient evidence to definitively determine the impact of physical activity interventions in ConHD. Further high-quality randomised controlled trials are therefore needed, utilising a longer duration of follow-up.
Abstract.
Author URL.
Musa DI, Toriola AL, Monyeki MA, Williams CA (2020). Relation of fitness and fatness with heart rate recovery after maximal exercise in Nigerian adolescents. Gazzetta Medica Italiana Archivio per le Scienze Mediche, 179(4).
Kelly AL, Wilson MR, Jackson DT, Turnnidge J, Williams CA (2020). Speed of Thought and Speed of Feet: Examining Perceptual-Cognitive Expertise and Physical Performance in an English Football Academy.
Journal of Science in Sport and Exercise,
3(1), 88-97.
Abstract:
Speed of Thought and Speed of Feet: Examining Perceptual-Cognitive Expertise and Physical Performance in an English Football Academy
AbstractThe world’s greatest professional football players are able to execute effective tactical decisions as well as fulfil various physical demands. However, the degree to which both are associated with greater potential in a football academy is unknown. Therefore, the aim of this study was to investigate decision-making skill and physical performance as contributing factors to coach potential rankings in an English football academy. Ninety-eight outfield academy players (Foundation Development Phase [FDP] under-9 to under-11 n = 40; Youth Development Phase [YDP] under-12 to under-16 n = 58) participated in the study. They engaged in 45 film-based simulations at two occlusion phases (e.g. the visual display is cut-off at a precise time during an action), firstly “during” and secondly “post” execution, to examine decision-making skill. Participants also completed four fitness tests to examine physical performance. A classification of “higher-potentials” (top third) and “lower-potentials” (bottom third) were applied through coach rankings. Independent t-tests compared the decision-making and physical performance tests. Higher-potentials made significantly more accurate decisions within the “post” phase within the FDP (P < 0.05) and the “during” phase within the YDP (P < 0.05). Additionally, higher-potentials were significantly faster for the 0–30 m sprint in both the FDP and YDP (P < 0.05), with higher-potentials within the YDP also significantly faster in the 0–10 m sprint (P < 0.05) and jumped significantly higher in the countermovement jump (P < 0.05). These findings indicated that greater football potential may be associated with superior perceptual-cognitive expertise and quicker sprint ability in both academy age phases, with a greater discriminatory function within the older cohort.
Abstract.
Kelly A, Wilson MR, Jackson DT, Williams CA (2020). Technical testing and match analysis statistics as part of the talent development process in an English football academy. International Journal of Performance Analysis in Sport, 20(6), 1035-1051.
GÄ
sior J, PawĆowski M, JeleĆ P, Rameckers E, Williams C, Makuch R, Werner B (2020). Test–Retest Reliability of Handgrip Strength Measurement in Children and Preadolescents.
International Journal of Environmental Research and Public Health,
17(21), 8026-8026.
Abstract:
TestâRetest Reliability of Handgrip Strength Measurement in Children and Preadolescents
The reliability of handgrip strength (HGS) measurement has been confirmed in adults but has been sparsely addressed in pediatric populations. The aims of this study are twofold: to determine whether sex, age and/or hand-dominance influence the test–retest differences and to establish the reliability level of the HGS measurement in typical developing pediatric participants. A total of 338 participants aged 7–13 years were tested using a digital handgrip strength (HGS) dynamometer (Jamar Plus+ Dynamometer) by the same rater on two testing trials separated by a one-day interval between sessions. The HGS testing was conducted according to the American Society of Hand Therapists recommendations. Relative and absolute reliability statistics were calculated. Age influenced the test–retest difference of the HGS measurement as children compared to preadolescents had lower intraclass correlation coefficients (0.95 vs. 0.98), standard error of measurement (SEM) (0.74 vs. 0.78 kg), smallest detectable difference (SDD) (2.05 vs. 2.16 kg) and higher values of the percentage value of SEM (5.48 vs. 3.44%), normalized SDD (15.52 vs. 9.61%) and a mean difference between the test and retest values (0.50 vs. 0.02 kg) for the dominant hand. The results indicate that the protocol using the Jamar digital handgrip dynamometer is a reliable instrument to measure HGS in participants aged 7–13 years with typical development. Clinicians and researchers therefore can have confidence in determining the minimally clinical effect for HGS.
Abstract.
Wadey CA, Weston ME, Dorobantu DM, Taylor RS, Pieles GE, Barker AR, Williams CA (2020). The role of cardiopulmonary exercise testing (CPET) in predicting mortality and morbidity in people with congenital heart disease: a systematic review and meta-analysis (Protocol).
Journal of Congenital Cardiology,
4(1).
Abstract:
The role of cardiopulmonary exercise testing (CPET) in predicting mortality and morbidity in people with congenital heart disease: a systematic review and meta-analysis (Protocol)
Abstract
Background
Numerous studies have measured the prognostic associations between cardiorespiratory fitness and patient outcomes in congenital heart disease, but no systematic review has assessed these associations for all types of congenital heart disease. It is therefore a timely opportunity to syntheses all available data using a systematic review methodology. The aim of this study is to detail the protocol for a systematic review and meta-analysis.
Objectives
Within this paper we have developed a protocol for a prognostic factors systematic review and meta-analysis, to assess the role of cardiopulmonary exercise testing/cardiorespiratory fitness, in the prognosis of mortality and morbidity in congenital heart disease.
Methods
We have outlined, in detail, the process for this systematic review using the latest accepted methodological guidelines for prognostic factors research, such as the PICOTS system, CHARMS-PF data extraction, QUIPS risk of bias assessments and the prognostic GRADE guidelines (see list of abbreviations).
Conclusion
The implications of this review will aid future treatments, interventions and individual patient risk prediction. The publication of this protocol aims to improve scientific rigour by ensuring transparency in the systematic review and meta-analysis process.
Abstract.
Kelly AL, Wilson MR, Gough LA, Knapman H, Morgan P, Cole M, Jackson DT, Williams CA (2019). A longitudinal investigation into the relative age effect in an English professional football club: exploring the ‘underdog hypothesis’. Science and Medicine in Football, 4(2), 111-118.
Cox NS, Eldridge B, Rawlings S, Dreger J, Corda J, Hauser J, Button BM, Bishop J, Nichols A, Middleton A, et al (2019). A web-based intervention to promote physical activity in adolescents and young adults with cystic fibrosis: protocol for a randomized controlled trial.
BMC Pulm Med,
19(1).
Abstract:
A web-based intervention to promote physical activity in adolescents and young adults with cystic fibrosis: protocol for a randomized controlled trial.
BACKGROUND: Regular participation in physical activity by people with cystic fibrosis (CF) promotes positive clinical and health outcomes including reduced rate of decline in lung function, fewer hospitalizations and greater wellbeing. However adherence to exercise and activity programs is low, in part due to the substantial daily therapy burden for young people with CF. Strict infection control requirements limit the role of group exercise programs that are commonly used in other clinical groups. Investigation of methods to promote physical activity in this group has been limited. The Active Online Physical Activity in Cystic fibrosis Trial (ActionPACT) is an assessor-blinded, multi-centre, randomized controlled trial designed to compare the efficacy of a novel web-based program (ActivOnline) compared to usual care in promoting physical activity participation in adolescents and young adults with CF. METHODS: Adolescents and young adults with CF will be recruited on discharge from hospital for a respiratory exacerbation. Participants randomized to the intervention group will have access to a web-based physical activity platform for the 12-week intervention period. ActivOnline allows users to track their physical activity, set goals, and self-monitor progress. All participants in both groups will be provided with standardised information regarding general physical activity recommendations for adolescents and young adults. Outcomes will be assessed by a blinded assessor at baseline, after completion of the intervention, and at 3-months followup. Healthcare utilization will be assessed at 12 months from intervention completion. The primary outcome is change in moderate-to-vigorous physical activity participation measured objectively by accelerometry. Secondary outcomes include aerobic fitness, health-related quality of life, anxiety and depression and sleep quality. DISCUSSION: This trial will establish whether a web-based application can improve physical activity participation more effectively than usual care in the period following hospitalization for a respiratory exacerbation. The web-based application under investigation can be made readily and widely available to all individuals with CF, to support physical activity and exercise participation at a time and location of the user's choosing, regardless of microbiological status. TRIAL REGISTRATION: Clinical trial registered on July 13, 2017 with the Australian and New Zealand Clinical Trials Register at (ACTRN12617001009303).
Abstract.
Author URL.
Tomlinson O, Barker A, Williams C (2019). Cardiopulmonary exercise testing in young people with cystic fibrosis. The Sport and Exercise Scientist, 61, 22-22.
Williams CA, Wedgwood KCA, Mohammadi H, Prouse K, Tomlinson OW, Tsaneva-Atanasova K (2019). Cardiopulmonary responses to maximal aerobic exercise in patients with cystic fibrosis.
PLoS ONE,
14Abstract:
Cardiopulmonary responses to maximal aerobic exercise in patients with cystic fibrosis
Cystic fibrosis (CF) is a debilitating chronic condition, which requires complex and expensive disease management. Exercise has now been recognised as a critical factor in improving health and quality of life in patients with CF. Hence, cardiopulmonary exercise testing (CPET) is used to determine aerobic fitness of young patients as part of the clinical management of CF. However, at present there is a lack of conclusive evidence for one limiting system of aerobic fitness for CF patients at individual patient level. Here, we perform detailed data analysis that allows us to identify important systems-level factors that affect aerobic fitness. We use patients’ data and principal component analysis to confirm the dependence of CPET performance on variables associated with ventilation and metabolic rates of oxygen consumption. We find that the time at which participants cross the gas exchange threshold (GET) is well correlated with their overall performance. Furthermore, we propose a predictive modelling framework that captures the relationship between ventilatory dynamics, lung capacity and function and performance in CPET within a group of children and adolescents with CF. Specifically, we show that using Gaussian processes (GP) we can predict GET at the individual patient level with reasonable accuracy given the small sample size of the available group of patients. We conclude by presenting an example and future perspectives for improving and extending the proposed framework. The modelling and analysis have the potential to pave the way to designing personalised exercise programmes that are tailored to specific individual needs relative to patient’s treatment therapies.
Abstract.
Oliveira RS, Barker AR, Debras F, Kranen SH, Williams CA (2019). Effects of exercise intensity on vascular and autonomic components of the baroreflex following glucose ingestion in adolescents.
Eur J Appl Physiol,
119(4), 867-878.
Abstract:
Effects of exercise intensity on vascular and autonomic components of the baroreflex following glucose ingestion in adolescents.
PURPOSE: to investigate the effects of an oral glucose tolerance test (OGTT) on baroreflex sensitivity (BRS) in a sample of healthy adolescents, and how acute exercise bouts of different intensities alter the effects of the OGTT on BRS. METHODS: Thirteen male adolescents (14.0 ± 0.5 years) completed three conditions on separate days in a counterbalanced order: (1) high-intensity interval exercise (HIIE); (2) moderate-intensity interval exercise (MIIE); and (3) resting control (CON). At ~ 90 min following the conditions, participants performed an OGTT. Supine heart rate and blood pressure were monitored continuously at baseline, 60 min following the conditions, and 60 min following the OGTT. A cross-spectral method (LFgain) was used to determine BRS gain. Arterial compliance (AC) was assessed as the BRS vascular component. LFgain divided by AC (LFgain/AC) was used as the autonomic component. RESULTS: Although non-significant, LFgain moderately decreased post-OGTT when no exercise was performed (pre-OGTT = 24.4 ± 8.2 ms mmHg- 1; post-OGTT = 19.9 ± 5.6 ms mmHg- 1; ES = 0.64, P > 0.05). This was attributed to the decrease in LFgain/AC (pre-OGTT = 1.19 ± 0.5 ms µm- 1; post-OGTT = 0.92 ± 0.24 ms µm- 1; ES = 0.69, P > 0.05). Compared to CON (Δ = - 4.4 ± 8.7 ms mmHg- 1), there were no differences for the pre-post-OGTT delta changes in LF/gain for HIIE (Δ = - 3.5 ± 8.2 ms mmHg- 1) and MIIE (Δ = 1.3 ± 9.9 ms mmHg- 1) had no effects on BRS following the OGTT (all ES
Abstract.
Author URL.
Williams CAP, Malik A, Barker A, Weston K (2019). Perceptual and Cardiorespiratory Responses to High-Intensity Interval Exercise in Adolescents: Does Work Intensity Matter?. Journal of Sports Science and Medicine
Williams CA, Wadey C, Pieles G, Stuart G, Taylor RS, Long L (2019). Physical activity interventions for people with congenital heart disease.
Cochrane Database of Systematic Reviews,
2019(8).
Abstract:
Physical activity interventions for people with congenital heart disease
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: to assess the effectiveness and safety of physical activity promotion and exercise training interventions in individuals with congenital heart disease.
Abstract.
Williams CA, Wadey C, Pieles G, Stuart G, Taylor RS, Long L (2019). Physical activity interventions for people with congenital heart disease. Cochrane Database of Systematic Reviews
Williams CA, Barker AR, Tomlinson OW (2019). Prediction of peak oxygen uptake using the modified shuttle test - Methodological concerns and implications for clinical practice.
Pediatr Pulmonol,
54(8), 1104-1105.
Author URL.
Denford S, Mackintosh KA, McNarry MA, Barker AR, Williams CA (2019). Promotion of physical activity for adolescents with cystic fibrosis: a qualitative study of UK multi-disciplinary cystic fibrosis teams. Physiotherapy
Kranen SH, Bond B, Williams CA, Barker AR (2019). Reliability of low-flow vasoreactivity in the brachial artery of adolescents.
Journal of Clinical Ultrasound,
47(3), 133-138.
Abstract:
Reliability of low-flow vasoreactivity in the brachial artery of adolescents
Purpose: Macrovascular endothelial function is commonly assessed using flow-mediated dilation (FMD) and is nitric oxide (NO) dependent. However, the vasoreactivity to low flow during the FMD protocol may complement FMD interpretation. This study aimed to investigate in adolescents: (1) the day-to-day reliability of low-flow-mediated constriction (L-FMC) and composite vessel reactivity (CVR); and (2) the relationship between L-FMC and FMD. Methods: a retrospective analysis of data on 27 adolescents (14.3 ± 0.6 year, 12 males) was performed. Participants had two repeat measures, on separate days, of macrovascular function using high-resolution ultrasound for assessment of L-FMC, FMD, and CVR. Results: on average, the L-FMC response was vasoconstriction on both days (−0.59 ± 2.22% and −0.16 ± 1.50%, respectively). In contrast, an inconsistent response to low flow (vasoconstriction, dilation, or no change) was observed on an individual level. Cohen's Kappa revealed poor agreement for classifying the L-FMC measurement between visits (k = 0.04, P >.05). Assessment of the actual vessel diameter was robust with a coefficient of variation of 1.7% (baseline and peak) and 2.7% (low-flow). The between-day correlation coefficient between measures was r =.18, r =.96 and r =.52 for L-FMC, FMD, and CVR, respectively. No significant correlation between FMD and L-FMC was observed for either visit (r = −.06 and r = −.07, respectively; P >.05). Conclusion: in adolescents, the low-flow vasoreactivity is inconsistent between days. Whereas the actual vessel diameter is reproducible, the measurement of L-FMC and CVR has poor between-day reliability compared to FMD. Finally, L-FMC, and FMD are not significantly correlated.
Abstract.
Mann RH, Williams CA, Clift BC, Barker AR (2019). The Validation of Session Rating of Perceived Exertion for Quantifying Internal Training Load in Adolescent Distance Runners.
Int J Sports Physiol Perform,
14(3), 354-359.
Abstract:
The Validation of Session Rating of Perceived Exertion for Quantifying Internal Training Load in Adolescent Distance Runners.
PURPOSE: to investigate the effect of measurement timing and concurrent validity of session and differential ratings of perceived exertion (sRPE and dRPE, respectively) as measures of internal training load in adolescent distance runners. METHODS: a total of 15 adolescent distance runners (15.2 [1.6] y) performed a 2-part incremental treadmill test for the assessment of maximal oxygen uptake, heart rate (HR), and blood lactate responses. Participants were familiarized with RPE and dRPE during the treadmill test using the Foster modified CR-10 Borg scale. Subsequently, each participant completed a regular 2-wk mesocycle of training. Participants wore an HR monitor for each exercise session and recorded their training in a logbook, including sRPE, dRPE leg exertion (dRPE-L), and breathlessness (dRPE-B) following session completion (0 min), 15 min postsession, and 30 min postsession. RESULTS: sRPE, dRPE-L, and dRPE-B scores were all most likely lower when reported 30 min postsession compared with scores 0 min postsession (%change, ±90% confidence limits; sRPE -26.5%, ±5.5%; dRPE-L -20.5%, ±5.6%; dRPE-B -38.9%, ±7.4%). sRPE, dRPE-L, and dRPE-B all maintained their largest correlations (r = .74-.89) when reported at session completion (0 min) in comparison with each of the HR-based criteria measures. CONCLUSION: sRPE, whether reported 0, 15, or 30 min postsession, provides a valid measure of internal training load in adolescent distance runners. In addition, dRPE-L and dRPE-B can be used in conjunction with sRPE across all time points (0, 15, and 30 min) to discriminate between central and peripheral exertion.
Abstract.
Author URL.
Cockcroft EJ, Bond B, Williams CA, Harris S, Jackman SR, Armstrong N, Barker AR (2019). The effects of two weeks high-intensity interval training on fasting glucose, glucose tolerance and insulin resistance in adolescent boys: a pilot study.
BMC Sports Science, Medicine and Rehabilitation,
11(1).
Abstract:
The effects of two weeks high-intensity interval training on fasting glucose, glucose tolerance and insulin resistance in adolescent boys: a pilot study
Abstract
. Background
. Current evidence of metabolic health benefits of high-intensity interval training (HIIT) are limited to longer training periods or conducted in overweight youth. This study assessed 1) fasting and postprandial insulin and glucose before and after 2 weeks of HIIT in healthy adolescent boys, and 2) the relationship between pre intervention health outcomes and the effects of the HIIT intervention.
.
. Methods
. Seven healthy boys (age:14.3 ± 0.3 y, BMI: 21.6 ± 2.6, 3 participants classified as overweight) completed 6 sessions of HIIT over 2 weeks. Insulin resistance (IR) and blood glucose and insulin responses to a Mixed Meal Tolerance Test (MMTT) were assessed before (PRE), 20 h and 70 h after (POST) the final HIIT session.
.
. Results
. Two weeks of HIIT had no effect on fasting plasma glucose, insulin or IR at 20 h and 70 h POST HIIT, nor insulin and glucose response to MMTT (all P > 0.05). There was a strong negative correlation between PRE training IR and change in IR after HIIT (r = − 0.96, P < 0.05).
.
. Conclusion
. Two weeks of HIIT did not elicit improvements to fasting or postprandial glucose or insulin health outcomes in a group of adolescent boys. However the negative correlation between PRE IR and improvements after HIIT suggest that interventions of this type may be effective in adolescents with raised baseline IR.
.
Abstract.
Sansum KM, Weston ME, Bond B, Cockcroft EJ, O'Connor A, Tomlinson OW, Williams CA, Barker AR (2019). Validity of the Supramaximal Test to Verify Maximal Oxygen Uptake in Children and Adolescents.
Pediatr Exerc Sci,
31(2), 213-222.
Abstract:
Validity of the Supramaximal Test to Verify Maximal Oxygen Uptake in Children and Adolescents.
Purpose: This study had 2 objectives: (1) to examine whether the validity of the supramaximal verification test for maximal oxygen uptake ( VËO2max ) differs in children and adolescents when stratified for sex, body mass, and cardiorespiratory fitness and (2) to assess sensitivity and specificity of primary and secondary objective criteria from the incremental test to verify VËO2max. Methods: in total, 128 children and adolescents (76 male and 52 females; age: 9.3-17.4 y) performed a ramp-incremental test to exhaustion on a cycle ergometer followed by a supramaximal test to verify VËO2max. Results: Supramaximal tests verified VËO2max in 88% of participants. Group incremental test peak VËO2 was greater than the supramaximal test (2.27 [0.65] L·min-1 and 2.17 [0.63] L·min-1; P
Abstract.
Author URL.
Vahia D, Kelly A, Knapman H, Williams CA (2019). Variation in the Correlation Between Heart Rate and Session Rating of Perceived Exertion-Based Estimations of Internal Training Load in Youth Soccer Players.
Pediatr Exerc Sci,
31(1), 91-98.
Abstract:
Variation in the Correlation Between Heart Rate and Session Rating of Perceived Exertion-Based Estimations of Internal Training Load in Youth Soccer Players.
PURPOSE: When exposed to the same external load, players receive different internal loads, resulting in varied adaptations in fitness. In adult soccer, internal training load is measured using heart rate (HR) and session rating of perceived exertion (sRPE) scales, but these have been underutilized in youth soccer. This study investigated the in-season variation in correlation between HR and sRPE estimations of training load for adolescent soccer players. METHOD: Fifteen male professional adolescent players were monitored for 7 months. Within-participant correlations and Bland-Altman agreement plots for HR and sRPE were calculated for each month to analyze variation over the season and for individual players to analyze the validity of the scale. RESULTS: the monthly correlations ranged from r = .60 to r = .73 (P
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Vlachopoulos D, Barker AR, Ubago-Guisado E, Williams CA, Gracia-Marco L (2018). A 9-Month Jumping Intervention to Improve Bone Geometry in Adolescent Male Athletes.
Med Sci Sports Exerc,
50(12), 2544-2554.
Abstract:
A 9-Month Jumping Intervention to Improve Bone Geometry in Adolescent Male Athletes.
PURPOSE: Sports have different effects on bone development and effective interventions to improve bone health of adolescent athletes are needed. The purpose of the study was to investigate the effect of a 9-month jumping intervention on bone geometry and metabolism in adolescent male athletes. METHODS: Ninety-three adolescent (14.1 yr old) male swimmers (SWI), footballers (FOO), and cyclists (CYC) were randomized to intervention and sport (INT-SWI = 19, INT-FOO = 15, and INT-CYC = 14) or sport only (CON-SWI = 18, CON-FOO = 15, and CON-CYC = 12) groups. Cross-sectional area, cross-sectional moment of inertia (CSMI), and section modulus (Z) at the femoral neck were assessed using hip structural analysis and trabecular texture of the lumbar spine using trabecular bone score. Bone mineral content (BMC) at femoral neck and lumbar spine was assessed using dual-energy x-ray absorptiometry. Serum N-terminal propeptide of procollagen type I, isomer of the carboxy-terminal telopeptide of type 1 collagen, total serum calcium, and 25-hydroxyvitamin D were analyzed. RESULTS: INT-CYC acquired significantly higher lumbar spine BMC (4.6%) and femoral neck BMC (9.8%) than CON-CYC. INT-CYC acquired significantly higher cross-sectional area (11.0%), CSMI (10.1%), and trabecular bone score (4.4%) than CON-CYC. INT-SWI acquired significantly higher femoral neck BMC (6.0%) and CSMI (10.9%) than CON-SWI. There were no significant differences between INT-FOO and CON-FOO in any bone outcomes. N-terminal propeptide of procollagen type I significantly decreased in CON-SWI, INT-FOO, CON-FOO, and CON-CYC. Carboxy-terminal telopeptide of type 1 collagen significantly decreased in CON-SWI and CON-CYC. The 25-hydroxyvitamin D significantly increased in INT-CYC, CON-CYC, INT-FOO, and CON-FOO. CONCLUSIONS: a 9-month jumping intervention improved bone outcomes in adolescent swimmers and cyclists, but not in footballers. This intervention might be used by sports clubs to improve bone health of adolescent athletes.
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Vlachopoulos D, Barker AR, Ubago-Guisado E, Williams CA, Gracia-Marco L (2018). A 9-month Jumping Intervention to Improve Bone Acquisition in Adolescent Male Athletes. Medicine & Science in Sports & Exercise, 50(5S).
Cockcroft EJ, Williams CA, Jackman SR, Bassi S, Armstrong N, Barker AR (2018). A single bout of high-intensity interval exercise and work-matched moderate-intensity exercise has minimal effect on glucose tolerance and insulin sensitivity in 7- to 10-year-old boys.
Journal of Sports Sciences,
36(2), 149-155.
Abstract:
A single bout of high-intensity interval exercise and work-matched moderate-intensity exercise has minimal effect on glucose tolerance and insulin sensitivity in 7- to 10-year-old boys
The purpose of this study was to assess the acute effect of high-intensity interval exercise (HIIE) and moderate-intensity exercise (MIE) on glucose tolerance, insulin sensitivity and fat oxidation in young boys. Eleven boys (8.8 ± 0.8 y) completed three conditions: 1) HIIE; 2) work-matched MIE; and 3) rest (CON) followed by an oral glucose tolerance test (OGTT) to determine glucose tolerance and insulin sensitivity (Cederholm index). Fat oxidation was measured following the OGTT using indirect calorimetry. There was no effect for condition on plasma [glucose] and [insulin] area under the curve (AUC) responses following the OGTT (P > 0.09). However, there was a “trend” for a condition effect for insulin sensitivity with a small increase after HIIE (P = 0.04, ES = 0.28, 9.7%) and MIE (P = 0.07, ES = 0.21, 6.5%) compared to CON. There was an increase in fat oxidation AUC following HIIE (P = 0.008, ES = 0.79, 38.9%) compared to CON, but with no differences between MIE and CON and HIIE and MIE (P > 0.13). In conclusion, 7- to 10-year-old boys may have limited scope to improve insulin sensitivity and glucose tolerance after a single bout of HIIE and MIE. However, fat oxidation is augmented after HIIE but not MIE.
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Varley-Campbell JL, Fulford J, Moore MS, Williams CA (2018). Adolescent brain activation: dependence on sex, dietary satiation, and restraint.
Nutr Neurosci,
21(6), 439-446.
Abstract:
Adolescent brain activation: dependence on sex, dietary satiation, and restraint.
The study aimed to explore how both sex and dietary restraint impacts brain activation in response to visual food stimuli in young adolescents (12-13 years) under fed and fasted conditions. Food and non-food images were viewed by 15 boys and 14 girls, while functional magnetic resonance images were acquired. The adolescents were either fasted or in a satiated (fed) state following a randomized crossover study design. When satiation state was not considered, girls showed significantly greater brain activity than boys in regions associated with executive function and decision making, working memory, and self-awareness. In contrast, when either fasted or fed states were considered separately, boys showed significantly increased brain activity in regions linked to executive function, self-awareness, and decision making than the girls. When fasted, compared to unrestrained eaters, restrained individuals showed heightened activation in regions connected to executive function and decision making, with areas associated with self-assessment showing increased activity for unrestrained eaters relative to restrained under fed conditions. These findings highlight important differences in adolescent brain activity and support further investigations to gain greater insight into how these differences might evolve with age.
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Tomlinson OW, Barker AR, Chubbock LV, Stevens D, Saynor ZL, Oades PJ, Williams CA (2018). Analysis of oxygen uptake efficiency parameters in young people with cystic fibrosis. European Journal of Applied Physiology, 118(10), 2055-2063.
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sior JS, PawĆowski M, Williams CA, DÄ
browski MJ, Rameckers EA (2018). Assessment of Maximal Isometric Hand Grip Strength in School-aged Children.
Open Med (Wars),
13, 22-28.
Abstract:
Assessment of Maximal Isometric Hand Grip Strength in School-aged Children.
BACKGROUND: Hand grip strength (HGS) test is commonly used as an indicator of overall muscle strength in medical and sport practices. Recently, several studies have proposed that the measurement of the maximal HGS depends on dynamometer's handle position. The aim of the present study was to identify the optimal handle position to obtain maximal HGS using the hand grip dynamometer (HGD) for school-aged children. METHODS: HGS was assessed with the Jamar digital HGD. Each participant performed three maximum contractions of each hand on three handle positions progressing from first to third position. RESULTS: a total of 135 healthy children aged 5-9 years participated in the study. Participants obtained significantly higher results using position 2 than using positions 1 or 3. The maximal mean (± SD) HGS achieved was 9.9 (± 3.1) kg with position 1, 10.4 (± 3.1) kg with position 2, and 9.0 (± 3.2) kg with position 3. Handle position 2 was the most comfortable position for 73% of participants. CONCLUSIONS: Our results provide useful methodological information indicating that the second handle position of the Jamar digital HGD is optimal to measure maximal HGS in non-athletic healthy pediatric participants aged 5-9 years.
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Oliveira RS, Barker AR, Williams CA (2018). Cardiac Autonomic Function, Cardiovascular Risk and Physical Activity in Adolescents.
Int J Sports Med,
39(2), 89-96.
Abstract:
Cardiac Autonomic Function, Cardiovascular Risk and Physical Activity in Adolescents.
The aims of this study were to investigate in adolescents: 1) the relationships of physical activity (PA) and cardiorespiratory fitness (CRF) to traditional CVD risk factors, rest and recovery autonomic function; and 2) whether autonomic function strengthens the associations between PA, CRF and CVD risk. Fifty-four (22 girls) adolescents had traditional CVD risk factors, rest and recovery autonomic function evaluated. CRF was measured using a steep ramp cycle test and PA was assessed with accelerometers. Resting HRV (and RMSSD30) and heart rate recovery (T30, HHRτ) were used. Clustered traditional (CVDRtrad) and autonomic (CVDRauto) risk scores were created and added to form a composite clustered CVD risk score (CVDRcom). PA and CRF were significantly and negatively associated with traditional CVD risk factors. Moderate (MPA) and vigorous (VPA) were positively related to resting RMSSD, and negatively related to T30 and HHRτ (all P
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Williams CA (2018). Elite Youth Sports-The Year That Was 2017.
Pediatr Exerc Sci,
30(1), 25-27.
Abstract:
Elite Youth Sports-The Year That Was 2017.
In 2017, considerable attention has been paid by researchers on early sports specialization for youth athletes. Issues related to injury, burnout, and talent development to name a few have been debated, particularly when contrasted against other opposing youth development approaches, such as a multisport approach. The increasing professionalization of young athletes, a particular concern of this author, is coupled with the ensuing physical and mental pressures on these youngsters, as highlighted by the 2 highlighted publications in this commentary. Moreover, the financial costs to parents to support talented youngsters lead me to conclude that we must not treat them as "mini-adult athletes." Trying to predict too far into the sporting future of a 9- or 10-year athlete can lead us to forgetting that they are just a 9 year, who typically wants to play, have fun, and be with their friends. Embarking on concentrated training programs, endless travel for tournaments, and an overemphasis on winning can be detrimental to participation rates as shown by recent data in the United States. Therefore, the challenge for researchers in elite youth sports is to ensure that practices we pursue with our young charges promote their health and well-being and that sports is for the benefit of the athlete and not the other way around.
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Brito J, Williams CA, Randers MB (2018). Executive summary: Recreational football training as medicine.
Scand J Med Sci Sports,
28 Suppl 1, 74-76.
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Patikas DA, Williams CA, Ratel S (2018). Exercise-induced fatigue in young people: advances and future perspectives.
European Journal of Applied Physiology,
118(5), 899-910.
Abstract:
Exercise-induced fatigue in young people: advances and future perspectives
Purpose: in recent decades, the interest for exercise-induced fatigue in youth has substantially increased, and the effects of growth on the peripheral (muscular) and central (neural) mechanisms underpinning differences in neuromuscular fatigue between healthy children and adults have been described more extensively. The purpose of this review is to retrieve, report, and analyse the findings of studies comparing neuromuscular fatigue between children and adults. Objective measures of the evaluation of the physiological mechanisms are discussed. Method: Major databases (PubMed, Ovid, Scopus and Web of Science) were systematically searched and limited to English language from inception to September 2017. Result: Collectively, the analyzed studies indicate that children experience less muscular and potentially more neural fatigue than adults. However, there are still many unknown aspects of fatigue regarding neural (supraspinal and spinal) and peripheral mechanisms that should be more thoroughly examined in children. Conclusion: Suitable methods, such as transcranial magnetic stimulation, transcranial electrical stimulation, functional magnetic resonance imaging, near-infrared spectroscopy, tendon vibration, H-reflex, and ultrasound are recommended in the research field of fatigue in youth. By designing studies that test the fatigue effects in movements that replicate daily activities, new knowledge will be acquired. The linkage and interaction between physiological, cognitive, and psychological aspects of human performance remain to be resolved in young people. This can only be successful if research is based on a foundation of basic research focused on the mechanisms of fatigue while measuring all three above aspects.
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Oliveira R, Barker AR, Debras F, O'Doherty A, Williams CA (2018). Mechanisms of blood pressure control following acute exercise in adolescents: Effects of exercise intensity on haemodynamics and baroreflex sensitivity.
Exp Physiol,
103(8), 1056-1066.
Abstract:
Mechanisms of blood pressure control following acute exercise in adolescents: Effects of exercise intensity on haemodynamics and baroreflex sensitivity.
NEW FINDINGS: What is the central question of this study? What are the autonomic and vascular components of the baroreflex during hypotension following different exercise intensities in adolescents? What is the main finding and its importance? Hypotension after high-intensity exercise lasted 60 min, whereas following moderate-intensity exercise, blood pressure was restored after 20 min. Stroke volume and peripheral resistance responses were different between intensities. Post both exercise intensities, baroreflex sensitivity was lowered mainly due to the autonomic component, which returned to baseline 60 min post-exercise. The different haemodynamic stimuli indicate potential differences in cardiovascular health benefits of exercise intensity in healthy adolescents. ABSTRACT: This work aimed to investigate the time course of changes in baroreflex sensitivity (BRS) and its vascular and autonomic components after different exercise intensities in adolescents. Thirteen male adolescents (age 13.9 ± 0.5 years) completed on separate days in a counterbalanced order (1) high-intensity interval exercise (HIIE): 8 × 1 min running at 90% of maximal aerobic speed with 75 s of active recovery; (2) moderate-intensity interval exercise (MIIE): 10-12 bouts of 1 min running at 90% of gas exchange threshold with 75 s of active recovery; and (3) resting as a control. Supine heart rate and blood pressure were monitored continuously at baseline, and 5 and 60 min following the conditions. A cross-spectral method (low frequency gain; LFgain ) was used to determine BRS gain. Arterial compliance (AC) was assessed as the BRS vascular component. LFgain /AC was used as the autonomic component. LFgain decreased 5 min post-exercise bouts (HIIE P
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Malik AA, Williams CA, Weston KL, Barker AR (2018). Perceptual Responses to High- and Moderate-Intensity Interval Exercise in Adolescents.
Med Sci Sports Exerc,
50(5), 1021-1030.
Abstract:
Perceptual Responses to High- and Moderate-Intensity Interval Exercise in Adolescents.
PURPOSE: Continuous high-intensity exercise is proposed to evoke unpleasant sensations as predicted by the dual-mode theory and may negatively impact on future exercise adherence. Previous studies support unpleasant sensations in affective responses during continuous high-intensity exercise, but the affect experience during high-intensity interval exercise (HIIE) involving brief bursts of high-intensity exercise separated by low-intensity activity is poorly understood in adolescents. We examined the acute affective, enjoyment, and perceived exertion responses to HIIE compared with moderate-intensity interval exercise (MIIE) in adolescents. METHODS: Thirteen adolescent boys (mean ± SD: age, 14.0 ± 0.5 yr) performed two counterbalanced exercise conditions: 1) HIIE: 8 × 1-min work intervals at 90% maximal aerobic speed; and 2) MIIE: between 9 and 12 × 1-min work intervals at 90% ventilatory threshold where the number of intervals performed were distance-matched to HIIE. HIIE and MIIE work intervals were interspersed with 75 s active recovery at 4 km·h. Affect, enjoyment, and RPE were recorded before, during, and after exercise. RESULTS: Affect responses declined in both conditions but the fall was greater in HIIE than MIIE (P < 0.025, effect size [ES], 0.64 to 0.81). Affect remained positive at the end-work interval for both conditions (MIIE, 2.62 ± 1.50; HIIE, 1.15 ± 2.08 on feeling scale). No enjoyment differences were evident during HIIE and MIIE (P = 0.32), but HIIE elicited greater postexercise enjoyment compared with MIIE (P = 0.01, ES = 0.47). RPE was significantly higher during HIIE than MIIE across all work intervals (all P < 0.03, ES > 0.64). CONCLUSIONS: Despite elevated RPE, HIIE did not elicit prominent unpleasant feelings as predicted by the dual-mode theory and was associated with greater postexercise enjoyment responses than MIIE. This study demonstrates the feasibility of the application of HIIE as an alternative form of physical activity in adolescents.
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Malik AA, Williams CA, Weston KL, Barker AR (2018). Perceptual and prefrontal cortex haemodynamic responses to high-intensity interval exercise with decreasing and increasing work-intensity in adolescents.
Int J Psychophysiol,
133, 140-148.
Abstract:
Perceptual and prefrontal cortex haemodynamic responses to high-intensity interval exercise with decreasing and increasing work-intensity in adolescents.
OBJECTIVES: Affect experienced during high-intensity interval exercise (HIIE) is dependent on work-intensity, but the influence of increasing (low-to-high (L-H)) or decreasing (high-to-low (H-L)) work-intensity during HIIE remains unclear in adolescents. The role of prefrontal cortex haemodynamics in mediating changes in affect during HIIE also remains unexplored in adolescents. We examined affect, enjoyment and cerebral haemodynamic responses to HIIE with increasing or decreasing work intensities in adolescents. METHODS: Participants (NâŻ=âŻ16; 8 boys; age 12.5⯱âŻ0.8âŻyears) performed, on separate days, HIIE cycling consisting of 8âŻ×âŻ1-min work-intervals at 100%-to-70% (HIIEH-L), 70%-to-100% (HIIEL-H) or 85% (HIIECON) peak power separated by 75âŻs recovery. Affect, enjoyment and cerebral haemodynamics (oxygenation (âO2Hb), deoxygenation (âHHb) and tissue oxygenation index (TOI)) were recorded before, during, and after all conditions. RESULTS: Affect and enjoyment were lower during HIIEH-L compared to HIIEL-H and HIIECON at work-intervals 1 to 3 (all PâŻâŻ0.83) but were greater during HIIEH-L than HIIEL-H and HIIECON at work-interval 8 (all PâŻâŻ0.83). âO2Hb was similar across conditions (PâŻ=âŻ0.87) but TOI and âHHb were significantly greater and lower, respectively during HIIEH-L compared to HIIEL-H and HIIECON at work-interval 8 (all PâŻâŻ0.40). Affect was correlated with TOI (all râŻ>âŻ0.92) and âHHb (all râŻ>âŻ-0.73) across conditions. CONCLUSIONS: HIIEH-L offers advancement to the HIIECON and HIIEL-H which bring significant greater affect and enjoyment towards the end HIIE work-interval, implicating the feasibility and adoption of this protocol for health promotion in youth. Also, changes in prefrontal cortex haemodynamics are associated with the affect during HIIE.
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Tomlinson OW, Shelley J, Denford S, Barker AR, Oades PJ, Williams CA (2018). Promotion of exercise in the management of cystic fibrosis - summary of national meetings.
European Journal for Person Centered Healthcare,
6(2), 196-196.
Abstract:
Promotion of exercise in the management of cystic fibrosis - summary of national meetings
Rationale, aims and objectives: Physical activity (PA) and exercise are important in maintaining and improving health and wellbeing in people with cystic fibrosis (CF) and measures of exercise capacity are useful outcomes in monitoring disease progression. The roles and responsibilities of CF multi-disciplinary team (MDT) members in supporting PA and exercise have yet to be fully defined. This communication reports on national meetings of CF MDT staff whose interest is to improve and standardise person-centered exercise provision and testing as part of routine CF care. We also introduce the role of the physiotherapy technician in supporting PA interventions.Meetings: the two meetings covered a range of presentations, discussions and workshops, focusing on the role of exercise and PA in CF management. Forty people from 15 NHS Hospital Trusts and 3 universities were asked to provide feedback via a questionnaire.Results: the common roles and responsibilities of clinical staff involved in exercise testing and prescription are described, with a wide range of duties identified. In addition, physiotherapists were reported as the main MDT member responsible for exercise provision. The majority of teams reported discussing exercise at every clinical visit (57%) and felt confident in discussing exercise with patients (67%).Conclusions: While this report highlights the current provision of exercise in CF MDTs, it also provides insight into the resources MDTs may require in order to enhance the profile of exercise within CF services, including enhanced training, guidelines and standardised clinical roles.
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Oliveira RS, Barker AR, Debras F, O'Doherty A, Williams CA (2018). Reliability of autonomic and vascular components of baroreflex sensitivity in adolescents.
Clinical Physiology and Functional Imaging,
38(6), 986-993.
Abstract:
Reliability of autonomic and vascular components of baroreflex sensitivity in adolescents
Improvements in the autonomic and vascular systems are implicated in cardiovascular disease risk reduction. Baroreflex sensitivity (BRS) is composed of vascular and autonomic components. This study aimed to investigate between- and within-day reliability of BRS and its autonomic and vascular determinants in adolescents. Thirteen male adolescents (14·1 ± 0·5 y) participated in this study. For between-day reliability, participants completed four experimental visits separated by a minimum of 48-h. For within-day reliability, participants repeated BRS assessments three times in the morning with one hour between the measures. BRS was evaluated using the cross-spectral gain (LFgain) between blood pressure and heart rate interval. BRS was further divided into: 1) vascular component using arterial compliance (AC); and 2) autonomic component measured as LFgain divided by AC (LFgain/AC). LFgain, AC and LFgain/AC presented between-day coefficient of variation (CV) of 20%, 17%, and 20%, respectively. Similarly, variables associated with blood pressure control, such as cardiac output, mean arterial pressure, heart rate and total peripheral resistance, presented CVs ranging from 6% to 15%. Within-day reliability was poorer compared to between-day for LFgain (25%), AC (25%), and LFgain/AC (31%), as well as all hemodynamic variables (CVs from 11% to 22%, except heart rate with presented CV of 6%). This study indicates suitable between- and within-reliability of BRS and its autonomic and vascular determinants, as well as hemodynamic variables associated with BRS, in adolescents.
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Krustrup P, Williams CA, Mohr M, Hansen PR, Helge EW, Elbe A-M, de Sousa M, Dvorak J, Junge A, Hammami A, et al (2018). The "Football is Medicine" platform-scientific evidence, large-scale implementation of evidence-based concepts and future perspectives.
Scand J Med Sci Sports,
28 Suppl 1, 3-7.
Author URL.
Chatzinikolaou A, Michaloglou K, Avloniti A, Leontsini D, Deli CK, Vlachopoulos D, Gracia Marco L, Arsenis S, Athanailidis I, Draganidis D, et al (2018). The Trainability of Adolescent Soccer Players to Brief Periodized Complex Training. International Journal of Sports Physiology and Performance, 13, 645-655.
Vlachopoulos D, Barker AR, Ubago-Guisado E, Ortega FB, Krustrup P, Metcalf B, Castro Pinero J, Ruiz JR, Knapp KM, Williams CA, et al (2018). The effect of 12-month participation in osteogenic and non-osteogenic sports on bone development in adolescent male athletes. The PRO-BONE study.
J Sci Med Sport,
21(4), 404-409.
Abstract:
The effect of 12-month participation in osteogenic and non-osteogenic sports on bone development in adolescent male athletes. The PRO-BONE study.
OBJECTIVES: Research investigating the longitudinal effects of the most popular sports on bone development in adolescent males is scarce. The aim is to investigate the effect of 12-month participation in osteogenic and non-osteogenic sports on bone development. DESIGN: a 12-month study was conducted in adolescent males involved in football, swimming and cycling and compared with an active control group. METHODS: 116 adolescent males (13.1±0.1years at baseline): 37 footballers, 37 swimmers, 28 cyclists and 14 active controls were followed for 12 months. Bone mineral content (BMC) was measured by dual-energy X-ray absorptiometry, and bone stiffness was measured by quantitative ultrasound. Bone outcomes at 12 months were adjusted for baseline bone status, age, height, lean mass and moderate to vigorous physical activity. RESULTS: Footballers had higher improvement in adjusted BMC at the total body, total hip, shaft, Ward's triangle, legs and bone stiffness compared to cyclists (6.3-8.0%). Footballers had significantly higher adjusted BMC at total body, shaft and legs compared to swimmers (5.4-5.6%). There was no significant difference between swimmers and cyclists for any bone outcomes. Swimming and cycling participation resulted in non-significant lower bone development at most sites of the skeleton compared to controls (-4.3 to -0.6%). CONCLUSIONS: Football participation induces significantly greater improvements in BMC and bone stiffness over 12 months compared to cycling and swimming. CLINICAL TRIAL REGISTRATION: ISRCTN17982776.
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Vlachopoulos D, Barker AR, Ubago-Guisado E, Williams CA, Gracia-Marco L (2018). The effect of a high-impact jumping intervention on bone mass, bone stiffness and fitness parameters in adolescent athletes.
Arch Osteoporos,
13(1).
Abstract:
The effect of a high-impact jumping intervention on bone mass, bone stiffness and fitness parameters in adolescent athletes.
UNLABELLED: This study demonstrates that a 9-month jumping intervention can improve bone mass gains and physical fitness performance in adolescent males participating in non-osteogenic sports, such as swimming and cycling. PURPOSE: to examine the effect of a jumping intervention on bone mass, bone stiffness and fitness parameters in adolescents involved in different sports. METHODS: Ninety-three adolescent male swimmers (SWI), footballers (FOO) and cyclists (CYC) were randomised to intervention (INT) and sport (INT-SWI = 19, INT-FOO = 15, INT-CYC = 14) or sport only (CON-SWI = 18, CON-FOO = 15, CON-CYC = 12) groups. The 9-month jumping intervention consisted of 3 levels (12 weeks each) of 20 repetitions per set of counter movement jumps (CMJ) using adjustable weight vests (level 1 = 20 CMJ jumps/set, 0 kg, 3 sets/day, 3 times/week; level 2 = 20 CMJ jumps/set, 2 kg, 4 sets/day, 3 times/week; level 3 = 20 CMJ jumps/set, 5 kg, 4 sets/day, 4 times/week). Total body bone mineral content (BMC) at total body less head (TBLH) was measured using dual-energy X-ray absorptiometry and bone stiffness using quantitative ultrasound. Fitness was assessed using the 20-m shuttle run (20mSRT), CMJ and standing long jump (SLJ) tests. RESULTS: INT-SWI had significantly higher increase in BMC legs and bone stiffness compared to CON-SWI (4.2-12.7%). INT-CYC had significantly higher increase in BMC at TBLH and legs and bone stiffness compared to CON-CYC (5.0-12.3%). There were no significant differences between INT-FOO and CON-FOO in any bone outcomes (0.9-3.9%). The increase in CMJ performance was significantly higher in INT-SWI (3.1 cm) and INT-CYC (3.2 cm) compared to CON-SWI and CON-CYC groups, respectively. CONCLUSIONS: a 9-month jumping intervention can improve bone mass, bone stiffness and muscular fitness in adolescent males participating in non-osteogenic sports, such as swimming and cycling. CLINICAL TRIAL REGISTRATION: ISRCTN17982776.
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Williams CA, Tomlinson OW, Chubbock LV, Stevens D, Saynor ZL, Oades PJ, Barker AR (2018). The oxygen uptake efficiency slope is not a valid surrogate of aerobic fitness in cystic fibrosis.
Pediatr Pulmonol,
53(1), 36-42.
Abstract:
The oxygen uptake efficiency slope is not a valid surrogate of aerobic fitness in cystic fibrosis.
BACKGROUND: Maximal cardiopulmonary exercise testing is recommended on an annual basis for children with cystic fibrosis (CF), due to clinically useful prognostic information provided by maximal oxygen uptake (VÌO2max ). However, not all patients are able, or willing, to reach VÌO2max , and therefore submaximal alternatives are required. This study explored the validity of the oxygen uptake efficiency slope (OUES) as a submaximal measure of VÌO2max in children and adolescents with CF. METHODS: Data were collated from 72 cardiopulmonary exercise tests (36 CF, 36 controls), with OUES determined relative to maximal and submaximal parameters of exercise intensity, time, and individual metabolic thresholds. Pearson's correlation coefficients, independent t-tests, and factorial ANOVAs were used to determine validity. RESULTS: Significant (P 0.05). When split by VÌO2max tertiles, minimal significant differences were found between, and within, groups for OUES, indicating poor discrimination of VÌO2max. CONCLUSIONS: the OUES is not a valid (sub) maximal measure of VÌO2max in children and adolescents with mild-to-moderate CF. Clinicians should continue to use maximal markers (ie, VÌO2max ) of exercise capacity.
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Williams CA, Gowing L, Horn R, Stuart AG (2017). A survey of exercise advice and recommendations in United Kingdom paediatric cardiac clinics.
Cardiology in the Young,
27(5), 951-956.
Abstract:
A survey of exercise advice and recommendations in United Kingdom paediatric cardiac clinics
Background Physical activity and exercise have important health benefits for children and adolescents with CHD. The objective of this study was to survey the provision of advice and recommendations in United Kingdom paediatric CHD clinics. Methods a three-page questionnaire was sent out to paediatric cardiac consultants in the United Kingdom, paediatric consultants with expertise in cardiology, and nursing staff (Paediatricians with Expertise in Cardiology Special Interest Group), as well as all members of the British Congenital Cardiovascular Association. The aim of this questionnaire was to determine the extent and scope of current information provision and to assess the importance that clinicians place on this advice. Results There were 68 responses in total, and the data showed that, of these, 24 (36%) clinicians had never provided paediatric CHD patients with written advice about exercise. Only 27 (39%) clinicians provided physical activity advice at every appointment. Lack of time during consultation (n=39, 56.9%), lack of training (n=38, 55.2%), and uncertainty about appropriate recommendations (n=38, 55.2%) were identified as the main factors preventing clinicians from providing patients with advice about physical activity. Conclusion Although healthcare providers consider physical activity to be very important, the provision of clear, specific advice and recommendations is underutilised; therefore, more education and provision of resources to support the promotion of exercise need to be provided to clinicians and their support teams.
Abstract.
Williams CA, Gowing L, Horn R, Graham Stuart A (2017). A survey of exercise advice and recommendations in United Kingdom paediatric cardiac clinics - CORRIGENDUM.
Cardiol Young,
27(5).
Author URL.
Cockcroft EJ, Williams CA, Weaver H, O'Connor A, Jackman SR, Armstrong N, Barker AR (2017). Acute Exercise and Insulin Sensitivity in Boys: a Time-Course Study.
Int J Sports Med,
38(13), 967-974.
Abstract:
Acute Exercise and Insulin Sensitivity in Boys: a Time-Course Study.
This study examined the time course of adaptions in insulin sensitivity (IS) in adolescent boys after acute high-intensity interval exercise (HIIE) and moderate-intensity exercise (MIE). Eight boys (15.1±0.4 y) completed three 3-day experimental trials in a randomised order: 1) 8×1 min cycling at 90% peak power with 75 s recovery (HIIE); 2) cycling at 90% of gas exchange threshold for a duration to match work during HIIE (MIE); and 3) rest (CON). Plasma [glucose] and [insulin] were measured before (PRE-Ex), 24 and 48 h post (24 h-POST, 48 h-POST) in a fasted state, and 40 min (POST-Ex) and 24 h (24 h-POST) post in response to an oral glucose tolerance test (OGTT). IS was estimated using the Cederholm (OGTT) and HOMA (fasted) indices. There was no change to HOMA at 24 h or 48 h-POST (all P>0.05). IS from the OGTT was higher POST-EX for HIIE compared to CON (17.4%, P=0.010, ES=1.06), and a non-significant increase in IS after MIE compared to CON (9.0%, P=0.14, ES=0.59). At 24 h-POST, IS was higher following both HIIE and MIE compared to CON (HIIE: P=0.019, 13.2%, ES=0.88; MIE: 9.7%, P=0.024, ES=0.65). In conclusion, improvements to IS after a single bout of HIIE and MIE persist up to 24 h after exercise when assessed by OGTT.
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Malik AA, Williams CA, Bond B, Weston KL, Barker AR (2017). Acute cardiorespiratory, perceptual and enjoyment responses to high-intensity interval exercise in adolescents. European Journal of Sport Science, 17(10), 1335-1342.
Dormehl SJ, Robertson SJ, Barker AR, Williams CA (2017). Confirming the Value of Swimming-Performance Models for Adolescents.
Int J Sports Physiol Perform,
12(9), 1177-1185.
Abstract:
Confirming the Value of Swimming-Performance Models for Adolescents.
PURPOSE: to evaluate the efficacy of existing performance models to assess the progression of male and female adolescent swimmers through a quantitative and qualitative mixed-methods approach. METHODS: Fourteen published models were tested using retrospective data from an independent sample of Dutch junior national-level swimmers from when they were 12-18 y of age (n = 13). The degree of association by Pearson correlations was compared between the calculated differences from the models and quadratic functions derived from the Dutch junior national qualifying times. Swimmers were grouped based on their differences from the models and compared with their swimming histories that were extracted from questionnaires and follow-up interviews. RESULTS: Correlations of the deviations from both the models and quadratic functions derived from the Dutch qualifying times were all significant except for the 100-m breaststroke and butterfly and the 200-m freestyle for females (P <. 05). In addition, the 100-m freestyle and backstroke for males and 200-m freestyle for males and females were almost directly proportional. In general, deviations from the models were accounted for by the swimmers' training histories. Higher levels of retrospective motivation appeared to be synonymous with higher-level career performance. CONCLUSION: This mixed-methods approach helped confirm the validity of the models that were found to be applicable to adolescent swimmers at all levels, allowing coaches to track performance and set goals. The value of the models in being able to account for the expected performance gains during adolescence enables quantification of peripheral factors that could affect performance.
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Author URL.
Williams CA (2017). Elite Youth Sports-From Best Pediatric Science Practice to Sports Practice-2016.
Pediatr Exerc Sci,
29(1), 19-22.
Abstract:
Elite Youth Sports-From Best Pediatric Science Practice to Sports Practice-2016.
In my 2015 editorial, I selected two research publications with a focus on an applied sports sciences perspective. This year I have chosen to focus on two publications from a methodological viewpoint, highlighting the importance of laboratory procedures and extraction of data through a systematic review respectively. The first publication by Leites and colleagues (J Appl Physiol) addresses questions in relation to thermoregulation and carbohydrate metabolism in young people. This topic is difficult to conduct due to additional ethical and safety concerns due to exercising in the heat. Nonetheless, there are important basic science questions to be answered. Using a range of measurement techniques including rectal thermometry, 13C-enriched carbohydrate isotopes and procedures to standardize the heat stress equally between a group of men and boys, this project demonstrates an exemplary range of experimental skills. In my second selected paper by Lesinski et al. (Brit J Sports Med), both a systematic review and a meta-analyses were conducted to investigate the dose-response relationships of resistance training on physical performance in youth athletes. As the requirement for more evidence based practice is demanded, the move away from a narrative review to a more methodological and rigorous approach is to be encouraged. It is, in my opinion, a skill that we should be encouraging all our early career pediatric researchers to learn from the outset, the outcome of which can only make our discipline stronger.
Abstract.
Author URL.
Pieles GE, Husk V, Blackwell T, Wilson D, Collin SM, Williams CA, Stuart AG (2017). High g-Force Rollercoaster Rides Induce Sinus Tachycardia but No Cardiac Arrhythmias in Healthy Children.
Pediatr Cardiol,
38(1), 15-19.
Abstract:
High g-Force Rollercoaster Rides Induce Sinus Tachycardia but No Cardiac Arrhythmias in Healthy Children.
Theme park operators and medical professionals advise children with heart conditions against using rollercoaster rides, but these recommendations are not evidence-based. The underlying assumption is that the combination of adrenergic stimulation through stress and acceleration might trigger arrhythmias in susceptible individuals. We conducted a cross-sectional observational study to assess heart rate and rhythm in healthy children during commercial rollercoaster rides. Twenty healthy children (9 male) aged 11-15 (mean 13.3 ± 1.4) years underwent continuous heart rate and rhythm monitoring (2-lead ECG) from 5 min before until 10 min after each of 4 high speed (>50 km h-1), high g-force (>4) commercial rollercoaster rides. Total recording time was 13 h 20 min. No arrhythmic events were detected. Resting heart rate was 81 ± 10 b min-1 and increased to 158 ± 20 b·min-1 during rides. The highest mean HR (165 ± 23 b min-1) was observed on the ride with the lowest g-force (4.5 g), but one of the highest speeds (100 km h-1). Anticipatory tachycardia (126 ± 15 b min-1) within 5 min was frequently observed. A 10 min recovery HR (124 ± 17 b min-1) was 56 % greater than resting HR. The speed and g-force experienced on roller coasters induce sinus tachycardia but do not elicit pathological arrhythmias in healthy children.
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Author URL.
Cockcroft EJ, Moudiotis C, Kitchen J, Bond B, Williams CA, Barker AR (2017). High-intensity interval exercise and glycemic control in adolescents with type one diabetes mellitus: a case study.
Physiol Rep,
5(13).
Abstract:
High-intensity interval exercise and glycemic control in adolescents with type one diabetes mellitus: a case study.
Current physical activity guidelines for youth with type 1 diabetes (T1D) are poorly supported by empirical evidence and the optimal dose of physical activity to improve glycemic control is unknown. This case report documents the effect of acute high-intensity interval exercise (HIIE) and moderate-intensity exercise (MIE) on 24-h glycemic control in three adolescents with T1D using continuous glucose monitoring. Results highlight varied individual response to exercise across the participants. In two participants both MIE and HIIE resulted in a drop in blood glucose during exercise (-38 to -42% for MIE and -21-46% in HIIE) and in one participant both MIE and HIIE resulted in increased blood glucose (+19% and + 36%, respectively). Over the 24-h period average blood glucose was lower for all participants in the HIIE condition, and for two for the MIE condition, compared to no exercise. All three participants reported HIIE to be more enjoyable than MIE These data show both HIIE and MIE have the potential to improve short-term glycemic control in youth with T1D but HIIE was more enjoyable. Future work with a larger sample size is required to explore the potential for HIIE to improve health markers in youth with T1D.
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Author URL.
Oliveira RS, Barker AR, Wilkinson KM, Abbott RA, Williams CA (2017). Is cardiac autonomic function associated with cardiorespiratory fitness and physical activity in children and adolescents? a systematic review of cross-sectional studies.
Int J Cardiol,
236, 113-122.
Abstract:
Is cardiac autonomic function associated with cardiorespiratory fitness and physical activity in children and adolescents? a systematic review of cross-sectional studies.
BACKGROUND: Heart rate variability (HRV) is considered to explain improvements in cardiovascular health accrued by physical activity (PA) and cardiorespiratory fitness (CRF) over and above traditional cardiovascular risk factors. OBJECTIVE: to systematically address associations between HRV, PA and CRF in children and adolescents. DATA SOURCES: Medline, EMBASE, SportDISCUS and CINAHL Plus were searched on 5th September 2015 and updated on 4th August 2016. ELIGIBILITY CRITERIA: Observational studies comparing HRV in different groups of PA and CRF, and/or studies investigating associations between PA, CRF and HRV. Sports practices and PA intensities were also included. The square root of the mean of the sum of the squares of differences between adjacent RR intervals (RMSSD), the spectral density in the high (HF) and low (LF) frequency, and the LF/HF ratio were included. Risk of bias was assessed using the adapted Newcastle-Ottawa Scale (NOS). RESULTS: Heterogeneity exists in the assessment of the exposures and outcomes, and sample characteristics. Risk of bias (NOS) was observed in most of the studies. Studies with low risk of bias showed positive associations between moderate-to-vigorous PA and RMSSD. The evidence for the associations between PA and frequency indices is weak. Similarly, the evidence for the association between CRF and HRV is weak. CONCLUSIONS: Despite the heterogeneity in the studies, moderate-to-vigorous PA is positively associated with RMSSD, but less clear are the associations between CRF and HRV, as well as other PA intensities. Further research is needed to clarify the role of PA and CRF on HRV in children and adolescents.
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Vlachopoulos D, Barker AR, Ubago-Guisado E, Fatouros IG, Knapp KM, Williams CA, Gracia-Marco L (2017). Longitudinal Adaptations of Bone Mass, Geometry, and Metabolism in Adolescent Male Athletes: the PRO-BONE Study.
J Bone Miner Res,
32(11), 2269-2277.
Abstract:
Longitudinal Adaptations of Bone Mass, Geometry, and Metabolism in Adolescent Male Athletes: the PRO-BONE Study.
Adolescence is a crucial period for bone development, and exercise can enhance bone acquisition during this period of life. However, it is not known how the different loading sports practiced can affect bone acquisition in adolescent male athletes. Therefore, the purpose of the present study was to determine the 1-year longitudinal bone acquisition among adolescent males involved in osteogenic (football) and non-osteogenic (swimming and cycling) sports and to compare with active controls. A total of 116 adolescent males aged 12 to 14 years at baseline were followed for 1 year: 37 swimmers, 37 footballers, 28 cyclists, and 14 active controls. Bone mineral content (BMC) was assessed using dual-energy X-ray absorptiometry (DXA); cross-sectional area (CSA), cross-sectional moment of inertia (CSMI), and section modulus (Z) at the femoral neck was assessed using hip structural analysis (HSA); and bone texture of the lumbar spine was assessed using trabecular bone score (TBS). Serum N-terminal propeptide of procollagen type I (PINP), isomer of the Carboxi-terminal telopeptide of type 1 collagen (CTX-I), total serum calcium, and 25 hydroxyvitamin D [25(OH)D] were analyzed. Footballers had significantly higher adjusted BMC at the lumbar spine (7.0%) and femoral neck (5.0%) compared with cyclists, and significantly greater BMC at the lumbar spine (6.9%) compared with swimmers. Footballers presented significantly greater TBS (4.3%) compared with swimmers, and greater CSMI (10.2%), CSA (7.1%), Z (8.9%) and TBS (4.2%) compared with cyclists. No differences were noted between cyclists and swimmers, both groups had similar bone acquisition compared with controls. PINP was significantly higher in footballers and controls compared with cyclists and swimmers (3.3% to 6.0%), and 25(OH)D was significantly higher in footballers and cyclists compared with swimmers and controls (9.9% to 13.1%). These findings suggest that bone acquisition is higher in adolescent male footballers compared with swimmers and cyclists at the femoral neck and lumbar spine sites of the skeleton. © 2017 American Society for Bone and Mineral Research.
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Author URL.
Williams CA, Saynor ZL, Barker AR, Oades PJ, Tomlinson OW (2017). Measurement of VÌo2max in clinical groups is feasible and necessary.
J Appl Physiol (1985),
123(4).
Author URL.
Bond B, Weston KL, Williams CA, Barker AR (2017). Perspectives on high-intensity interval exercise for health promotion in children and adolescents.
Open Access J Sports Med,
8, 243-265.
Abstract:
Perspectives on high-intensity interval exercise for health promotion in children and adolescents.
Physical activity lowers future cardiovascular disease (CVD) risk; however, few children and adolescents achieve the recommended minimum amount of daily activity. Accordingly, there is virtue in identifying the efficacy of small volumes of high-intensity exercise for health benefits in children and adolescents for the primary prevention of CVD risk. The purpose of this narrative review is to provide a novel overview of the available literature concerning high-intensity interval-exercise (HIIE) interventions in children and adolescents. Specifically, the following areas are addressed: 1) outlining the health benefits observed following a single bout of HIIE, 2) reviewing the role of HIIE training in the management of pediatric obesity, and 3) discussing the effectiveness of school-based HIIE training. In total, 39 HIIE intervention studies were included in this review. Based upon the available data, a single bout of high-intensity exercise provides a potent stimulus for favorable, acute changes across a range of cardiometabolic outcomes that are often superior to a comparative bout of moderate-intensity exercise (14 studies reviewed). HIIE also promotes improvements in cardiorespiratory fitness and cardiometabolic health status in overweight and obese children and adolescents (10 studies reviewed) and when delivered in the school setting (15 studies reviewed). We thus conclude that high-intensity exercise is a feasible and potent method of improving a range of cardiometabolic outcomes in children and adolescents. However, further work is needed to optimize the delivery of HIIE interventions in terms of participant enjoyment and acceptability, to include a wider range of health outcomes, and to control for important confounding variables (eg, changes in diet and habitual physical activity). Finally, research into the application of HIIE training interventions to children and adolescents of different ages, sexes, pubertal status, and sociocultural backgrounds is required.
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Author URL.
Gelbart M, Ziv-Baran T, Williams CA, Yarom Y, Dubnov-Raz G (2017). Prediction of Maximal Heart Rate in Children and Adolescents.
Clin J Sport Med,
27(2), 139-144.
Abstract:
Prediction of Maximal Heart Rate in Children and Adolescents.
OBJECTIVE: to identify a method to predict the maximal heart rate (MHR) in children and adolescents, as available prediction equations developed for adults have a low accuracy in children. We hypothesized that MHR may be influenced by resting heart rate, anthropometric factors, or fitness level. DESIGN: Cross-sectional study. SETTING: Sports medicine center in primary care. PARTICIPANTS: Data from 627 treadmill maximal exercise tests performed by 433 pediatric athletes (age 13.7 ± 2.1 years, 70% males) were analyzed. INDEPENDENT VARIABLES: Age, sex, sport type, stature, body mass, BMI, body fat, fitness level, resting, and MHR were recorded. MAIN OUTCOME MEASURES: to develop a prediction equation for MHR in youth, using stepwise multivariate linear regression and linear mixed model. To determine correlations between existing prediction equations and pediatric MHR. RESULTS: Observed MHR was 197 ± 8.6 b·min. Regression analysis revealed that resting heart rate, fitness, body mass, and fat percent were predictors of MHR (R = 0.25, P < 0.001), whereas age was not. Resting heart rate explained 15.6% of MHR variance, body mass added 5.7%, fat percent added 2.4%, and fitness added 1.2%. Existing adult equations had low correlations with observed MHR in children and adolescents (r = -0.03-0.34). CONCLUSIONS: a new equation to predict MHR in children and adolescents was developed, but was found to have low predictive ability, a finding similar to adult equations applied to children. CLINICAL RELEVANCE: Considering the narrow range of MHR in youth, we propose using 197 b·min as the mean MHR in children and adolescents, with 180 b·min the minimal threshold value (-2 standard deviations).
Abstract.
Author URL.
Williams CA, Winsley RJ, Pinho G, de Ste Croix M, Lloyd RS, Oliver JL (2017). Prevalence of non-functional overreaching in elite male and female youth academy football players. Science and Medicine in Football, 1(3), 222-228.
Tomlinson OW, Barker AR, Oades PJ, Williams CA (2017). Scaling the oxygen uptake efficiency slope for body size in cystic fibrosis.
Medicine and Science in Sports and Exercise,
49(10), 1980-1986.
Abstract:
Scaling the oxygen uptake efficiency slope for body size in cystic fibrosis
© Copyright 2017 by the American College of Sports Medicine. Purpose the aim of this study was to describe the relationship between body size and oxygen uptake efficiency slope (OUES) in pediatric patients with cystic fibrosis (CF) and healthy controls (CON), to identify appropriate scaling procedures to adjust the influence of body size upon OUES. Methods the OUES was derived using maximal and submaximal points from cardiopulmonary exercise testing in 72 children (36 CF and 36 CON). OUES was subsequently scaled for stature, body mass (BM), and body surface area (BSA) using ratio-standard (Y/X) and allometric (Y/Xb) methods. Pearson's correlation coefficients were used to determine the relationship between body size and OUES. Results When scaled using the ratio-standard method, OUES had a significant positive relationship with stature (r = 0.54, P < 0.001) and BSA (r = 0.25, P = 0.031) and significant negative relationship with BM (r = -0.38, P = 0.016) in the CF group. Combined allometric exponents (b) for CF and CON were stature 3.00, BM 0.86, and BSA 1.40. A significant negative correlation was found between OUES and stature in the CF group when scaled allometrically (r = -0.37, P = 0.027). Nonsignificant (P > 0.05) correlations for the whole group were found between OUES and allometrically scaled BM (CF r = -0.25, CON, r = 0.15) and BSA (CF r = -0.27, CON r = 0.13). Conclusions Only allometric scaling of either BM or BSA, and not ratio-standard scaling, successfully eliminates the influence of body size upon OUES. Therefore, this enables a more direct comparison of the OUES between patients with CF and healthy controls.
Abstract.
Varley-Campbell JL, Moore MS, Williams CA (2017). The effects of a mid-morning snack and moderate-intensity exercise on acute appetite and energy intake in 12-14-year-old adolescents.
Br J Nutr,
117(4), 602-610.
Abstract:
The effects of a mid-morning snack and moderate-intensity exercise on acute appetite and energy intake in 12-14-year-old adolescents.
Energy intake (EI) and energy expenditure (EE) should not be considered independent entities, but more an inter-connected system. With increased physical activity and reduced snacking initiatives as prevalent Public Health measures, any changes to subsequent EI from these recommendations should be monitored. The aim of this study was to investigate changes in acute EI and appetite over four conditions: (1) a control condition with no snack and no exercise (CON); (2) a snack condition (+1 MJ; SK); (3) a moderate-intensity cycling exercise condition (-1 MJ; EX); and finally (4) both snack and exercise condition (+1 MJ, -1 MJ; EXSK). Acute changes in appetite (visual analogue scale) and lunchtime EI (ad libitum pizza meal) were recorded in twenty boys and eighteen girls (12-13 years). Lunch EI was not significantly different between conditions or sexes (P>0·05). Relative EI was calculated, where the energy manipulation (+1 MJ from the snack or -1 MJ from the exercise) was added to lunchtime EI. Relative EI indicated no significant differences between the sexes (P>0·05); however, in the EX condition, relative EI was significantly lower (P
Abstract.
Author URL.
Williams CAP, Vlachopoulos D, Barker AR, Arngrimsson SA, Knapp KM, Metcalf B, Moreno LA, Gracia-Marco L (2017). The impact of sport participation on bone mass and geometry in adolescent males. Medicine and Science in Sports and Exercise
Bond B, Williams CA, Barker AR (2017). The reliability of a single protocol to determine endothelial, microvascular and autonomic functions in adolescents.
Clin Physiol Funct Imaging,
37(6), 703-709.
Abstract:
The reliability of a single protocol to determine endothelial, microvascular and autonomic functions in adolescents.
BACKGROUND: Impairments in macrovascular, microvascular and autonomic function are present in asymptomatic youths with clustered cardiovascular disease risk factors. This study determines the within-day reliability and between-day reliability of a single protocol to non-invasively assess these outcomes in adolescents. METHODS: Forty 12- to 15-year-old adolescents (20 boys) visited the laboratory in a fasted state on two occasions, approximately 1 week apart. One hour after a standardized cereal breakfast, macrovascular function was determined via flow-mediated dilation (FMD). Heart rate variability (root mean square of successive R-R intervals; RMSSD) was determined from the ECG-gated ultrasound images acquired during the FMD protocol prior to cuff occlusion. Microvascular function was simultaneously quantified as the peak (PRH) and total (TRH) hyperaemic response to occlusion in the cutaneous circulation of the forearm via laser Doppler imaging. To address within-day reliability, a subset of twenty adolescents (10 boys) repeated these measures 90 min afterwards on one occasion. RESULTS: the within-day typical error and between-day typical error expressed as a coefficient of variation of these outcomes are as follows: ratio-scaled FMD, 5·1% and 10·6%; allometrically scaled FMD, 4·4% and 9·4%; PRH, 11% and 13·3%; TRH, 29·9% and 23·1%; and RMSSD, 17·6% and 17·6%. The within- and between-day test-retest correlation coefficients for these outcomes were all significant (r > 0·54 for all). CONCLUSION: Macrovascular, microvascular and autonomic functions can be simultaneously and non-invasively determined in adolescents using a single protocol with an appropriate degree of reproducibility. Determining these outcomes may provide greater understanding of the progression of cardiovascular disease and aid early intervention.
Abstract.
Author URL.
Armstrong N (2016). Aerobic Fitness and Training in Children and Adolescents.
Pediatr Exerc Sci,
28(1), 7-10.
Author URL.
Williams CA (2016). Elite Youth Sports.
Pediatr Exerc Sci,
28(1), 16-18.
Author URL.
Tomlinson OW, Barker AR, Oades PJ, Williams CA (2016). Exercise capacity following a percutaneous endoscopic gastrostomy in a young female with cystic fibrosis: a case report.
Physiological Reports,
4(16).
Abstract:
Exercise capacity following a percutaneous endoscopic gastrostomy in a young female with cystic fibrosis: a case report
Cystic fibrosis (CF) is a genetic condition affecting the respiratory and gastrointestinal systems, with patients experiencing problems maintaining weight, especially during rapid growth periods such as puberty. The aim of this case report was to monitor the effect of gastrostomy insertion and implementation of overnight supplemental feeding upon clinical outcomes, including body mass index (BMI), lung function (FEV1), and exercise-related variables (maximal oxygen uptake [VO2max] and ventilatory efficiency [VE/VO2]) in an 11-year-old female with CF. Combined incremental and supramaximal exercise testing to exhaustion was performed at four time points: 3 months prior to the procedure (T1), 2 days prior to (T2), 4 months (T3), and 1 year following the procedure (T4). Improvements following gastrostomy insertion were observed at the 1 year follow-up with regards to BMI (+20%); whereas absolute VO2max remained stable and lung function fluctuated throughout the period of observation. Declines in function with regards to body weight relative VO2max (−16.3%) and oxygen uptake efficiency (+7.5%) were observed during this period. This case report is the first to consider exercise-related clinical outcomes in assessing the effect of implementing gastrostomy feeding in CF. The varied direction and magnitude of the associations between variables shows that further investigations are required.
Abstract.
Dormehl SJ, Robertson SJ, Williams CA (2016). How Confident can We be in Modelling Female Swimming Performance in Adolescence?.
Sports (Basel),
4(1).
Abstract:
How Confident can We be in Modelling Female Swimming Performance in Adolescence?
The purpose of this research was to determine the expected progression of adolescent female swimming performances using a longitudinal approach. The performances of 514 female swimmers (12â»19 year olds) who participated in one or more FINA-regulated annual international schools' swimming championships over an eight-year period were analysed. Quadratic functions for each of the seven individual events (50, 100, 200 m freestyle, 100 m backstroke, breaststroke, butterfly, 200 m individual medley) were determined using mixed linear models. The predicted threshold of peak performance ranged from 16.8 ± 0.2 (200 m individual medley) to 20.6 ± 0.1 (100 m butterfly) years of age, preceded by gradual rates of improvement (mean rate of 1.6% per year). However, following cross validation, only three events (100 m backstroke, 200 m individual medley and 200 m freestyle) produced reliable models. Identifying the factors that contribute to the progression of female performance in this transitory period of life remains challenging, not least since the onset of puberty is likely to have occurred prior to reaching 12 years of age, the minimum competition age for this championship.
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Author URL.
Saynor ZL, Barker AR, Oades PJ, Williams CA (2016). Impaired Pulmonary VËO2 Kinetics in Cystic Fibrosis Depend on Exercise Intensity.
Med Sci Sports Exerc,
48(11), 2090-2099.
Abstract:
Impaired Pulmonary VËO2 Kinetics in Cystic Fibrosis Depend on Exercise Intensity.
PURPOSE: This study aimed to investigate the effects of mild-to-moderate cystic fibrosis (CF) on the pulmonary oxygen uptake (VËO2) kinetics of seven pediatric patients (13.5 ± 2.8 yr) versus seven healthy matched controls (CON; 13.6 ± 2.4 yr). We hypothesized that CF would slow the VËO2 kinetic response at the onset of moderate (MOD) and very heavy (VH) intensity cycling. METHODS: Changes in breath-by-breath VËO2, near-infrared spectroscopy-derived muscle deoxygenation ([HHb]) at the vastus lateralis muscle and thoracic bioelectrical impedance-derived heart rate (HR), stroke volume index, and cardiac index were measured during repeat transitions to MOD (90% of the gas exchange threshold) and VH (Δ60%) intensity cycling exercise. RESULTS: During MOD, the phase II VËO2 τ (P = 0.84, effect size [ES] = 0.11) and the overall mean response time (MRT) (P = 0.52, ES = 0.11) were not significantly slower in CF versus CON. However, during VH exercise, the phase II VËO2 τ (P = 0.02, ES = 1.28) and MRT (P = 0.01, ES = 1.40) were significantly slower in CF. Cardiac function, central O2 delivery (stroke volume index and cardiac index), and muscle [HHb] kinetics were unaltered in CF. However, the arteriovenous O2 content difference ((Equation is included in full-text article.)) was reduced during VH at 30 s (P = 0.03, ES = 0.37), with a trend for reduced levels at 0 s (P = 0.07, ES = 0.25), 60 s (P = 0.05, ES = 0.28), and 120 s (P = 0.07, ES = 0.25) in CF. Furthermore, (Equation is included in full-text article.)significantly correlated with the VH phase II VËO2 τ (r = -0.85, P = 0.02) and MRT (r = -0.79, P = 0.03) in CF only. CONCLUSION: Impairments in muscle oxidative metabolism during constant work rate exercise are intensity dependent in young people with mild-to-moderate CF. Specifically, VËO2 kinetics are slowed during VH but not MOD cycling and appear to be mechanistically linked to impaired muscle O2 extraction and utilization.
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Author URL.
Dormehl SJ, Robertson SJ, Williams CA (2016). Modelling the Progression of Male Swimmers' Performances through Adolescence.
Sports (Basel),
4(1).
Abstract:
Modelling the Progression of Male Swimmers' Performances through Adolescence.
Insufficient data on adolescent athletes is contributing to the challenges facing youth athletic development and accurate talent identification. The purpose of this study was to model the progression of male sub-elite swimmers' performances during adolescence. The performances of 446 males (12â»19 year olds) competing in seven individual events (50, 100, 200 m freestyle, 100 m backstroke, breaststroke, butterfly, 200 m individual medley) over an eight-year period at an annual international schools swimming championship, run under FINA regulations were collected. Quadratic functions for each event were determined using mixed linear models. Thresholds of peak performance were achieved between the ages of 18.5 ± 0.1 (50 m freestyle and 200 m individual medley) and 19.8 ± 0.1 (100 m butterfly) years. The slowest rate of improvement was observed in the 200 m individual medley (20.7%) and the highest in the 100 m butterfly (26.2%). Butterfly does however appear to be one of the last strokes in which males specialise. The models may be useful as talent identification tools, as they predict the age at which an average sub-elite swimmer could potentially peak. The expected rate of improvement could serve as a tool in which to monitor and evaluate benchmarks.
Abstract.
Author URL.
Williams CA (2016). Physical activity and health of adults with cystic fibrosis.
Respirology,
21(3), 404-405.
Author URL.
Dormehl SJ, Williams CA (2016). Stability of within-sport specialisation in competitive adolescent sub-elite swimmers.
INTERNATIONAL JOURNAL OF PERFORMANCE ANALYSIS IN SPORT,
16(1), 12-28.
Author URL.
Bangsbo J, Krustrup P, Duda J, Hillman C, Andersen LB, Weiss M, Williams CA, Lintunen T, Green K, Hansen PR, et al (2016). The Copenhagen Consensus Conference 2016: children, youth, and physical activity in schools and during leisure time.
Br J Sports Med,
50(19), 1177-1178.
Abstract:
The Copenhagen Consensus Conference 2016: children, youth, and physical activity in schools and during leisure time.
From 4 to 7 April 2016, 24 researchers from 8 countries and from a variety of academic disciplines gathered in Snekkersten, Denmark, to reach evidence-based consensus about physical activity in children and youth, that is, individuals between 6 and 18â
years. Physical activity is an overarching term that consists of many structured and unstructured forms within school and out-of-school-time contexts, including organised sport, physical education, outdoor recreation, motor skill development programmes, recess, and active transportation such as biking and walking. This consensus statement presents the accord on the effects of physical activity on children's and youth's fitness, health, cognitive functioning, engagement, motivation, psychological well-being and social inclusion, as well as presenting educational and physical activity implementation strategies. The consensus was obtained through an iterative process that began with presentation of the state-of-the art in each domain followed by plenary and group discussions. Ultimately, Consensus Conference participants reached agreement on the 21-item consensus statement.
Abstract.
Author URL.
Williams CA (2016). Trainability of Young Athletes: Short-Term Goals or Long-Term Mission?.
Pediatr Exerc Sci,
28(4), 485-487.
Author URL.
Saynor ZL, Barker AR, Oades PJ, Tomlinson OW, Williams CA (2016). Validity and Reliability Concerns Associated with Cardiopulmonary Exercise Testing Young People with Cystic Fibrosis. Respiration, 92(1), 61-62.
Bond B, Williams CA, Jackman SR, Woodward A, Armstrong N, Barker AR (2015). Accumulating exercise and postprandial health in adolescents.
Metabolism: clinical and experimentalAbstract:
Accumulating exercise and postprandial health in adolescents
Purpose: to examine the influence of exercise intensity on postprandial health outcomes in adolescents when exercise is accumulated throughout the day. Methods: 19 adolescents (9 male, 13.7 ± 0.4 y) completed three 1-day trials in a randomised order: 1) rest (CON); or four bouts of 2) 2 x 1 min cycling at 90% peak power with 75 s recovery (high-intensity interval exercise; HIIE); or 3) cycling at 90% of the gas exchange threshold (moderate-intensity exercise; MIE), which was work-matched to HIIE. Each bout was separated by 2 hours. Participants consumed a high fat milkshake for breakfast and lunch. Postprandial triacylglycerol (TAG), glucose, systolic blood pressure (SBP) and fat oxidation were assessed throughout the day. Results: There was no effect of trial on total area under the curve (TAUC) for TAG (P=0.87). TAUC-glucose was lower in HIIE compared to CON (P=0.03, ES=0.42) and MIE (P=0.04, ES=0.41), with no difference between MIE and CON (P=0.89, ES=0.04). Postprandial SBP was lower in HIIE compared to CON (P=0.04, ES=0.50) and MIE (P=0.04, ES=0.40), but not different between MIE and CON (P=0.52, ES=0.11). Resting fat oxidation was increased in HIIE compared to CON (P=0.01, ES=0.74) and MIE (P=0.05, ES=0.51), with no difference between MIE and CON (P=0.37, ES=0.24). Conclusion: Neither exercise trial attenuated postprandial lipaemia. However, accumulating brief bouts of HIIE, but not MIE, reduced postprandial plasma glucose and SBP, and increased resting fat oxidation in adolescent boys and girls. The intensity of accumulated exercise may therefore have important implications for health outcomes in youth.
Abstract.
McNarry MA, Farr C, Middlebrooke A, Welford D, Breese B, Armstrong N, Barker AR (2015). Aerobic Function and Muscle Deoxygenation Dynamics during Ramp Exercise in Children.
Med Sci Sports Exerc,
47(9), 1877-1884.
Abstract:
Aerobic Function and Muscle Deoxygenation Dynamics during Ramp Exercise in Children.
PURPOSE: This study aimed to characterize changes in deoxyhemoglobin ([HHb]) response dynamics in boys and girls during ramp incremental exercise to investigate whether the reduced peak oxygen uptake (peak VËO2) in girls is associated with poorer matching of muscle O2 delivery to muscle O2 utilization, as evidenced by a more rapid increase in [HHb]. METHODS: Fifty-two children (31 boys, 9.9 ± 0.6 yr, 1.38 ± 0.07 m, 31.70 ± 5.78 kg) completed ramp incremental exercise on a cycle ergometer during which pulmonary gas exchange and muscle oxygenation parameters were measured. RESULTS: When muscle [HHb] was expressed against absolute work rate and VËO2, girls had an earlier change in [HHb], as evidenced by the lower c/d parameter (girls, 54 ± 20 W, vs boys, 67 ± 19 W, P = 0.023; girls, 0.82 ± 0.28 L·min(-1), vs boys, 0.95 ± 0.19 L·min(-1), P = 0.055) and plateau (girls, 85 ± 12 W, vs boys, 99 ± 18 W, P = 0.031; girls, 1.02 ± 0.25 L·min(-1), vs boys, 1.22 ± 0.28 L·min(-1), P = 0.014). However, when expressed against relative work rate or VËO2, there were no sex differences in ([HHb]) response dynamics (all P > 0.20). Significant correlations were observed between absolute and fat-free mass normalized peak VËO2 and the HHb c/d and plateau parameters when expressed against absolute work rate or VËO2. Furthermore, when entered into a multiple regression model, the [HHb] plateau against absolute VËO2 contributed 12% of the variance in peak VËO2 after adjusting for fat-free mass, gas exchange threshold, and body fatness (model R2 = 0.81, P < 0.001). CONCLUSIONS: the sex difference in peak VËO2 in 9- to 10-yr-old children is, in part, related to sex-specific changes in muscle O2 extraction dynamics during incremental exercise.
Abstract.
Author URL.
Armstrong N (2015). Aerobic fitness and training in children.
Pediatr Exerc Sci,
27(1), 8-12.
Author URL.
Stevens D, Oades PJ, Williams CA (2015). Airflow limitation following cardiopulmonary exercise testing and heavy-intensity intermittent exercise in children with cystic fibrosis.
European Journal of Pediatrics,
174(2), 251-257.
Abstract:
Airflow limitation following cardiopulmonary exercise testing and heavy-intensity intermittent exercise in children with cystic fibrosis
The clinical importance of exercise testing and training in the healthcare management of young patients with cystic fibrosis (CF) is growing. The aim of the present study was to determine the incidence of airflow limitation following cardiopulmonary exercise testing (CPET) and heavy-intensity intermittent exercise (HIIE) in young patients with CF. Nineteen young patients with CF and respective paired–matched controls performed CPET and HIIE on separate days. Forced expiratory volume in one second (FEV1) was measured pre- and post each exercise modality. A fall in FEV1 of 10 % or greater was used to define airflow limitation. The incidence of airflow limitation was significantly greater in the CF group than in the controls following CPET (32 vs. 5 %; p = 0.03); however, no significant difference in the incidence of airflow limitation was shown following HIIE between the CF group and controls (11 vs. 16 %; p = 0.64). Conclusion: Our data show that the incidence of airflow limitation following CPET in young patients with CF is high. Therefore, clinicians may wish to identify whether young CF patients experience airflow limitation following strenuous exercise, such as CPET, before it is performed. However, HIIE carries a low risk for airflow limitation and may be prescribed as a safe, yet effective exercise modality for young patients with CF.
Abstract.
Nimmerichter A, Williams CA (2015). Comparison of power output during ergometer and track cycling in adolescent cyclists.
J Strength Cond Res,
29(4), 1049-1056.
Abstract:
Comparison of power output during ergometer and track cycling in adolescent cyclists.
The aim of this study is to establish the level of agreement between test performance of young elite cyclists in a laboratory and a track field-based trial. Fourteen adolescent cyclists (age: 14.8 ± 1.1 years; (Equation is included in full-text article.): 63.5 ± 5.6 ml·min(-1)·kg(-1)) performed 3 tests of 10 seconds, 1 minute, and 3 minutes on an air-braked ergometer (Wattbike) and on a 250-m track using their own bikes mounted with mobile power meters (SRM). The agreement between the maximum and mean power output (Pmax and Pmean) measured on the Wattbike and SRM was assessed with the 95% limits of agreement (LoA). Power output was strongly correlated between Wattbike and SRM for all tests (r = 0.94-0.96; p < 0.001). However, power output was significantly higher on the Wattbike compared with track cycling during all tests. The bias and 95% LoA were 76 ± 78 W (8.8 ± 9.5%; p = 0.003, d = 0.38) for Pmax10s and 82 ± 55 W (10.9 ± 7.9%; p < 0.001, d = 0.46) for Pmean10s. During the 1- and 3-minute test, the bias and 95% LoA were 72 ± 30 W (17.9 ± 7.1%; p < 0.001, d = 0.84) and 28 ± 20 W (9.6 ± 6.1%; p < 0.001, d = 0.51), respectively. Laboratory tests, as assessed using a stationary ergometer, resulted in maximal and mean power output scores that were consistently higher than a track field-based test using a mobile ergometer. These results might be attributed to the technical ability of the riders and their experience to optimize gearing and cadence to maximize performance. Prediction of field-based testing on the track from laboratory tests should be used with caution.
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Author URL.
Westendorf ML, Williams CA (2015). Effects of Excess Dietary Phosphorus on Fecal Phosphorus Excretion and Water Extractable Phosphorus in Horses.
Journal of Equine Veterinary Science,
35(6), 495-498.
Abstract:
Effects of Excess Dietary Phosphorus on Fecal Phosphorus Excretion and Water Extractable Phosphorus in Horses
Phosphorus excretion was studied in horses fed excess phosphorus. The hypothesis of this study was that the concentration of phosphorus and water extractable phosphorus (WEP) in the feces of sedentary horses would reflect the level of dietary phosphorus. Eight Standardbred mares were divided into two groups and received diets of grass hay and grain. The high phosphorus (HP) group received 142 g/d of monosodium phosphate (NaH2PO4), formulated to provide 4.5-times dietary phosphorus requirement, or 65-g phosphorus per day. The low phosphorus (LP) group received 28 g of phosphorus per day in the basal diet. These amounts were based on horses consuming 2% of body weight per day as hay plus supplemental grain. After a 7-day diet adaptation, a 5-day collection was conducted. Animals were housed from 4 PM until 8 AM the following morning without bedding during the collection period. After the first period, horses underwent a 10-day washout and then groups were crossed over for a second 7-day adaptation and 5-day collection. Feces was collected daily, weighed, and a 10% of aliquot taken. At the end of each collection period, feces was composited for each horse and analyzed for nitrogen, potassium, phosphorus, and WEP. Fecal phosphorus and WEP content were greater in theHP group (8.1 ± 0.3 vs. 6.8 ± 0.3 g/kg, respectively) than the LP group (3.6 ± 0.3 vs. 2.1± 0.3 g/kg, respectively; P <. 05). Overfeeding a phosphorus supplement increased phosphorus and WEP in the manure; WEP may be useful for determining phosphorus runoff risk.
Abstract.
Williams CA (2015). Elite youth sports.
Pediatr Exerc Sci,
27(1), 18-20.
Author URL.
Rosenblum O, Katz U, Reuveny R, Williams CA, Dubnov-Raz G (2015). Exercise Performance in Children and Young Adults After Complete and Incomplete Repair of Congenital Heart Disease.
Pediatric Cardiology,
36(8), 1573-1581.
Abstract:
Exercise Performance in Children and Young Adults After Complete and Incomplete Repair of Congenital Heart Disease
Few previous studies have addressed exercise capacity in patients with corrected congenital heart disease (CHD) and significant anatomical residua. The aim of this study was to determine the aerobic fitness and peak cardiac function of patients with corrected CHD with complete or incomplete repairs, as determined by resting echocardiography. Children, adolescents and young adults (
Abstract.
Rosenblum O, Katz U, Reuveny R, Williams CA, Dubnov-Raz G (2015). Exercise Performance in Children and Young Adults After Complete and Incomplete Repair of Congenital Heart Disease.
Pediatric CardiologyAbstract:
Exercise Performance in Children and Young Adults After Complete and Incomplete Repair of Congenital Heart Disease
Few previous studies have addressed exercise capacity in patients with corrected congenital heart disease (CHD) and significant anatomical residua. The aim of this study was to determine the aerobic fitness and peak cardiac function of patients with corrected CHD with complete or incomplete repairs, as determined by resting echocardiography. Children, adolescents and young adults (
Abstract.
Bond B, Williams CA, Isic C, Jackman SR, Tolfrey K, Barrett LA, Barker AR (2015). Exercise intensity and postprandial health outcomes in adolescents.
Eur J Appl Physiol,
115(5), 927-936.
Abstract:
Exercise intensity and postprandial health outcomes in adolescents.
PURPOSE: the effect of exercise intensity and sex on postprandial risk factors for cardiovascular disease in adolescents is unknown. We examined the effect of a single bout of work-matched high-intensity interval exercise (HIIE) and moderate-intensity exercise (MIE) on postprandial triacylglycerol (TAG) and systolic blood pressure (SBP) in adolescents. METHOD: Twenty adolescents (10 male, 14.3 ± 0.3 years) completed three 1-day trials: (1) rest (CON); (2) 8 × 1 min cycling at 90 % peak power with 75 s recovery (HIIE); (3) cycling at 90 % of the gas exchange threshold (MIE), 1 h before consuming a high-fat milkshake (1.50 g fat and 80 kJ kg(-1)). Postprandial TAG, SBP and fat oxidation were assessed over 4 h RESULTS: Compared to CON, the incremental area under the curve for TAG (IAUC-TAG) was not significantly lowered in HIIE [P = 0.22, effect size (ES) = 0.24] or MIE (P = 0.65, ES = 0.04) for boys. For girls, HIIE and MIE lowered IAUC-TAG by 34 % (P = 0.02, ES = 0.58) and 38 % (P = 0.09, ES = 0.73), respectively, with no difference between HIIE and MIE (P = 0.74, ES = 0.14). Changes in TAG were not related to energy expenditure during exercise or postprandial fat oxidation. Postprandial SBP (total-AUC pooled for both sexes) was lower in HIIE compared to CON (P = 0.01, ES = 0.68) and MIE (P = 0.02, ES = 0.60), with no difference between MIE and CON (P = 0.45, ES = 0.14). CONCLUSION: a single bout of HIIE and MIE, performed 1 h before an HFM, can meaningfully attenuate IAUC-TAG in girls but not boys. Additionally, HIIE, but not MIE, may lower postprandial SBP in normotensive adolescents.
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Author URL.
Bond B, Gates PE, Jackman SR, Corless LM, Williams CA, Barker AR (2015). Exercise intensity and the protection from postprandial vascular dysfunction in adolescents.
Am J Physiol Heart Circ Physiol,
308(11), H1443-H1450.
Abstract:
Exercise intensity and the protection from postprandial vascular dysfunction in adolescents.
Acute exercise transiently improves endothelial function and protects the vasculature from the deleterious effects of a high-fat meal (HFM). We sought to identify whether this response is dependent on exercise intensity in adolescents. Twenty adolescents (10 male, 14.3 ± 0.3 yr) completed three 1-day trials: 1) rest (CON); 2) 8 × 1 min cycling at 90% peak power with 75 s recovery [high-intensity interval exercise (HIIE)]; and 3) cycling at 90% of the gas exchange threshold [moderate-intensity exercise (MIE)] 1 h before consuming a HFM (1.50 g/kg fat). Macrovascular and microvascular endothelial function was assessed before and immediately after exercise and 3 h after the HFM by flow-mediated dilation (FMD) and laser Doppler imaging [peak reactive hyperemia (PRH)]. FMD and PRH increased 1 h after HIIE [P < 0.001, effect size (ES) = 1.20 and P = 0.048, ES = 0.56] but were unchanged after MIE. FMD and PRH were attenuated 3 h after the HFM in CON (P < 0.001, ES = 1.78 and P = 0.02, ES = 0.59). FMD remained greater 3 h after the HFM in HIIE compared with MIE (P < 0.001, ES = 1.47) and CON (P < 0.001, ES = 2.54), and in MIE compared with CON (P < 0.001, ES = 1.40). Compared with CON, PRH was greater 3 h after the HFM in HIIE (P = 0.02, ES = 0.71) and MIE (P = 0.02, ES = 0.84), with no differences between HIIE and MIE (P = 0.72, ES = 0.16). Plasma triacylglycerol concentration and total antioxidant status concentration were not different between trials. We conclude that exercise intensity plays an important role in protecting the vasculature from the deleterious effects of a HFM. Performing HIIE may provide superior vascular benefits than MIE in adolescent groups.
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Williams AJ, Wyatt KM, Williams CA, Logan S, Henley WE (2015). Exploring the Potential of a School Impact on Pupil Weight Status: Exploratory Factor Analysis and Repeat Cross-Sectional Study of the National Child Measurement Programme.
PLoS One,
10(12).
Abstract:
Exploring the Potential of a School Impact on Pupil Weight Status: Exploratory Factor Analysis and Repeat Cross-Sectional Study of the National Child Measurement Programme.
Schools are common sites for obesity prevention interventions. Although many theories suggest that the school context influences weight status, there has been little empirical research. The objective of this study was to explore whether features of the school context were consistently and meaningfully associated with pupil weight status (overweight or obese). Exploratory factor analysis of routinely collected data on 319 primary schools in Devon, England, was used to identify possible school-based contextual factors. Repeated cross-sectional multilevel analysis of five years (2006/07-2010/11) of data from the National Child Measurement Programme was then used to test for consistent and meaningful associations. Four school-based contextual factors were derived which ranked schools according to deprivation, location, resource and prioritisation of physical activity. None of which were meaningfully and consistently associated with pupil weight status, across the five years. The lack of consistent associations between the factors and pupil weight status suggests that the school context is not inherently obesogenic. In contrast, incorporating findings from education research indicates that schools may be equalising weight status, and obesity prevention research, policy and practice might need to address what is happening outside schools and particularly during the school holidays.
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Author URL.
Cockcroft EJ, Williams CA, Tomlinson OW, Vlachopoulos D, Jackman SR, Armstrong N, Barker AR (2015). High intensity interval exercise is an effective alternative to moderate intensity exercise for improving glucose tolerance and insulin sensitivity in adolescent boys.
J Sci Med Sport,
18(6), 720-724.
Abstract:
High intensity interval exercise is an effective alternative to moderate intensity exercise for improving glucose tolerance and insulin sensitivity in adolescent boys.
OBJECTIVES: High-intensity interval exercise (HIIE) may offer a time efficient means to improve health outcomes compared to moderate-intensity exercise (MIE). This study examined the acute effect of HIIE compared to a work-matched bout of MIE on glucose tolerance, insulin sensitivity (IS), resting fat oxidation and exercise enjoyment in adolescent boys. DESIGN: Within-measures design with counterbalanced experimental conditions. METHODS: Nine boys (14.2 ± 0.4 years) completed three conditions on separate days in a counterbalanced order: (1) HIIE; (2) work matched MIE, both on a cycle ergometer; and (3) rest (CON). An oral glucose tolerance test (OGTT) was performed after exercise or rest and the area under curve (AUC) responses for plasma [glucose] and [insulin] were calculated, and IS estimated (Cederholm index). Energy expenditure and fat oxidation were measured following the OGTT using indirect calorimetry. Exercise enjoyment was assessed using the Physical Activity Enjoyment Scale. RESULTS: the incremental AUC (iAUC) for plasma [glucose] was reduced following both MIE (-23.9%, P = 0.013, effect size [ES] = -0.64) and HIIE (-28.9%, P=0.008, ES = -0.84) compared to CON. The iAUC for plasma [insulin] was lower for HIIE (-24.2%, P = 0.021, ES = -0.71) and MIE (-29.1%, P = 0.012, ES = -0.79) compared to CON. IS increased by 11.2% after HIIE (P = 0.03, ES = 0.76) and 8.4% after MIE (P = 0.10, ES = 0.58). There was a trend for an increase in fat oxidation following HIIE (P = 0.097, ES = 0.70). Both HIIE and MIE were rated as equally enjoyable (P > 0.05, ES < 0.01). CONCLUSION: a single bout of time efficient HIIE is an effective alternative to MIE for improving glucose tolerance and IS in adolescent boys immediately after exercise.
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Lloyd RS, Oliver JL, Faigenbaum AD, Howard R, De Ste Croix MBA, Williams CA, Best TM, Alvar BA, Micheli LJ, Thomas DP, et al (2015). Long-term athletic development, part 2: barriers to success and potential solutions.
J Strength Cond Res,
29(5), 1451-1464.
Abstract:
Long-term athletic development, part 2: barriers to success and potential solutions.
The first installment of this two-part commentary reviewed existing models of long-term athletic development. However, irrespective of the model that is adopted by practitioners, existing structures within competitive youth sports in addition to the prevalence of physical inactivity in a growing number of modern-day youth may serve as potential barriers to the success of any developmental pathway. The second part of this commentary will initially highlight common issues that are likely to impede the success of long-term athletic development programs and then propose solutions that will address the negative impact of such issues.
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Lloyd RS, Oliver JL, Faigenbaum AD, Howard R, De Ste Croix MBA, Williams CA, Best TM, Alvar BA, Micheli LJ, Thomas DP, et al (2015). Long-term athletic development- part 1: a pathway for all youth.
J Strength Cond Res,
29(5), 1439-1450.
Abstract:
Long-term athletic development- part 1: a pathway for all youth.
The concept of developing talent and athleticism in youth is the goal of many coaches and sports systems. Consequently, an increasing number of sporting organizations have adopted long-term athletic development models in an attempt to provide a structured approach to the training of youth. It is clear that maximizing sporting talent is an important goal of long-term athletic development models. However, ensuring that youth of all ages and abilities are provided with a strategic plan for the development of their health and physical fitness is also important to maximize physical activity participation rates, reduce the risk of sport- and activity-related injury, and to ensure long-term health and well-being. Critical reviews of independent models of long-term athletic development are already present within the literature; however, to the best of our knowledge, a comprehensive examination and review of the most prominent models does not exist. Additionally, considerations of modern day issues that may impact on the success of any long-term athletic development model are lacking, as are proposed solutions to address such issues. Therefore, within this 2-part commentary, Part 1 provides a critical review of existing models of practice for long-term athletic development and introduces a composite youth development model that includes the integration of talent, psychosocial and physical development across maturation. Part 2 identifies limiting factors that may restrict the success of such models and offers potential solutions.
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Armstrong N, Barker AR, McManus AM (2015). Muscle metabolism changes with age and maturation: How do they relate to youth sport performance?.
Br J Sports Med,
49(13), 860-864.
Abstract:
Muscle metabolism changes with age and maturation: How do they relate to youth sport performance?
AIM: to provide an evidence-based review of muscle metabolism changes with sex-, age- and maturation with reference to the development of youth sport performance. METHODS: a narrative review of data from both invasive and non-invasive studies, from 1970 to 2015, founded on personal databases supported with computer searches of PubMed and Google Scholar. RESULTS: Youth sport performance is underpinned by sex-, age- and maturation-related changes in muscle metabolism. Investigations of muscle size, structure and metabolism; substrate utilisation; pulmonary oxygen uptake kinetics; muscle phosphocreatine kinetics; peak anaerobic and aerobic performance; and fatigue resistance; determined using a range of conventional and emerging techniques present a consistent picture. Age-related changes have been consistently documented but specific and independent maturation-related effects on muscle metabolism during exercise have proved elusive to establish. Children are better equipped for exercise supported primarily by oxidative metabolism than by anaerobic metabolism. Sexual dimorphism is apparent in several physiological variables underpinning youth sport performance. As young people mature there is a progressive but asynchronous transition into an adult metabolic profile. CONCLUSIONS: the application of recent developments in technology to the laboratory study of the exercising child and adolescent has both supplemented existing knowledge and provided novel insights into developmental exercise physiology. A sound foundation of laboratory-based knowledge has been established but the lack of rigorously designed child-specific and sport-specific testing environments has clouded the interpretation of the data in real life situations. The primary challenge remains the translation of laboratory research into the optimisation of youth sports participation and performance.
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Varley-Campbell JL, Moore MS, Ewen RE, Williams CA (2015). Perceived energy compensation following various sports: an age and sex comparison. Preliminary observations.
Eur J Clin Nutr,
69(12), 1344-1345.
Abstract:
Perceived energy compensation following various sports: an age and sex comparison. Preliminary observations.
Following periods of physical activity, it is not uncommon for exercisers to increase their energy intake as a reward deemed 'earned'. Consumers' awareness of the energy within food and expended from exercise has previously been found to be limited. Therefore, the aim was to investigate whether habitual exercisers (50 adults and 49 children from 5 sports clubs) were able to conceptualise the energy expenditure (EE), following 1 h of their regular sports training, into a quantifiable amount of perceived energy compensation (PEC) in the form of food (chocolate) or drink (sports drink). Mean percentage accuracy for the PEC against EE matched
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Nimmerichter A, Steindl M, Williams C (2015). Reliability of the Single-Visit Field Test of Critical Speed in Trained and Untrained Adolescents. Sports, 3(4), 358-368.
Fulford J, Varley-Campbell JL, Williams CA (2015). The effect of breakfast versus no breakfast on brain activity in adolescents when performing cognitive tasks, as assessed by fMRI. Nutritional Neuroscience, 19(3), 110-115.
Pieles GE, Gowing L, Forsey J, Ramanujam P, Miller F, Stuart AG, Williams CA (2015). The relationship between biventricular myocardial performance and metabolic parameters during incremental exercise and recovery in healthy adolescents.
Am J Physiol Heart Circ Physiol,
309(12), H2067-H2076.
Abstract:
The relationship between biventricular myocardial performance and metabolic parameters during incremental exercise and recovery in healthy adolescents.
Background left ventricular (LV) and right ventricular (RV) myocardial reserve during exercise in adolescents has not been directly characterized. The aim of this study was to quantify myocardial performance response to exercise by using two-dimensional (2-D) speckle tracking echocardiography and describe the relationship between myocardial reserve, respiratory, and metabolic exercise parameters. A total of 23 healthy boys and girls (mean age 13.2 ± 2.7 yr; stature 159.1 ± 16.4 cm; body mass 49.5 ± 16.6 kg; BSA 1.47 ± 0.33 m(2)) completed an incremental cardiopulmonary exercise test (25 W · 3 min increments) with simultaneous acquisition of 2-D transthoracic echocardiography at rest, each exercise stage up to 100 W, and in recovery at 2 min and 10 min. Two-dimensional LV (LV Sl) and RV (RV Sl) longitudinal strain and LV circumferential strain (LV Sc) were analyzed to define the relationship between myocardial performance reserve and metabolic exercise parameters. Participants achieved a peak oxygen uptake (VÌo 2peak) of 40.6 ± 8.9 ml · kg(-1) · min(-1) and a work rate of 154 ± 42 W. LV Sl and LV Sc and RV Sl increased significantly across work rates (P < 0.05). LV Sl during exercise was significantly correlated to resting strain, VÌo 2peak, oxygen pulse, and work rate (0.530 ≤ r ≤ 0.784, P < 0.05). This study identifies a positive and moderate relationship between LV and RV myocardial performance and metabolic parameters during exercise by using a novel methodology. Relationships detected present novel data directly describing myocardial adaptation at different stages of exercise and recovery that in the future can help directly assess cardiac reserve in patients with cardiac pathology.
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Bond B, Cockcroft EJ, Williams CA, Harris S, Gates PE, Jackman SR, Armstrong N, Barker AR (2015). Two weeks of high-intensity interval training improves novel but not traditional cardiovascular disease risk factors in adolescents.
Am J Physiol Heart Circ Physiol,
309(6), H1039-H1047.
Abstract:
Two weeks of high-intensity interval training improves novel but not traditional cardiovascular disease risk factors in adolescents.
High-intensity interval training (HIIT) improves traditional cardiovascular disease (CVD) risk factors in adolescents, but no study has identified the influence of HIIT on endothelial and autonomic function in this group. Thirteen 13- to 14-yr-old adolescents (6 girls) completed six HIIT sessions over 2 wk. Each training session consisted of eight to ten 1-min repetitions of cycling at 90% peak power interspersed with 75 s of unloaded cycling. Traditional (triglycerides, cholesterol, glucose, insulin, and blood pressure) and novel [flow-mediated dilation (FMD), heart rate variability (HRV)] CVD risk factors were assessed in a fasted and postprandial state before (PRE), 1 day after (POST-1D), and 3 days after (POST-3D) training. Aerobic fitness was determined PRE and POST-3D. Two weeks of HIIT had no effect on aerobic fitness or traditional CVD risk factors determined in the fasted or postprandial state (P > 0.15). Compared with PRE, fasted FMD was improved POST-1D [P = 0.003, effect size (ES) = 0.70] but not POST-3D (P = 0.32, ES = 0.22). Fasted FMD was greater POST-1D compared with POST-3D (P = 0.04, ES = 0.48). Compared with PRE, postprandial FMD was greater POST-1D (P < 0.001, ES = 1.01) and POST-3D (P = 0.01, ES = 0.60). Fasted HRV was greater POST-1D (P = 0.001, ES = 0.71) and POST-3D (P = 0.02, ES = 0.44). The test meal lowered HRV in all laboratory visits (P < 0.001, ES = 0.59), but there were no differences in postprandial HRV between visits (P > 0.32 for all). Two weeks of HIIT enhanced endothelial function and HRV without improvements in traditional CVD risk factors. However, most of this favorable adaptation was lost POST-3D, suggesting that regularly performing high-intensity exercise is needed to maintain these benefits.
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Author URL.
Williams AJ, Wyatt KM, Williams CA, Logan S, Henley WE (2014). A repeated cross-sectional study examining the school impact on child weight status.
Prev Med,
64(100), 103-107.
Abstract:
A repeated cross-sectional study examining the school impact on child weight status.
OBJECTIVE: the aim of this study is to examine whether there is a differential impact of primary schools upon children's weight status. METHODS: a repeated cross-sectional study was undertaken using five years (2006/07-2010/11) of National Child Measurement Programme data, comprising 57,976 children (aged 4-5 (Reception) and 10-11 (Year 6) years) from 300 primary schools across Devon, England. Examining each year separately, the schools were ranked according to their observed and residual (having accounted for school and neighbourhood clustering and pupil ethnicity and socioeconomic status) school mean body mass index standard deviation score (BMI-SDS). Subtracting the Reception from the Year 6 mean residuals gave 'value-added' scores for each school which were also ranked. The rankings were compared within and across the years to assess consistency. RESULTS: Although pupil BMI-SDS was high, >97% of the variation in BMI-SDS was attributable to environments other than the school. The 'value-added' by each school was only poorly correlated with the observed and residual pupil BMI-SDS; but none of the rankings were consistent across the five years. CONCLUSION: the inconsistency of the rankings and the small variation in BMI-SDS at the level of the school suggests that there is no systematic differential impact of primary schools upon pupil weight status.
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Pieles GE, Szantho G, Rodrigues JCL, Lawton CB, Stuart AG, Bucciarelli-Ducci C, Turner MS, Williams CA, Tulloh RMR, Hamilton MCK, et al (2014). Adaptations of aortic and pulmonary artery flow parameters measured by phase-contrast magnetic resonance angiography during supine aerobic exercise. European Journal of Applied Physiology, 1-11.
Pieles GE, Szantho G, Rodrigues JCL, Lawton CB, Stuart AG, Bucciarelli-Ducci C, Turner MS, Williams CA, Tulloh RMR, Hamilton MCK, et al (2014). Adaptations of aortic and pulmonary artery flow parameters measured by phase-contrast magnetic resonance angiography during supine aerobic exercise.
EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY,
114(5), 1013-1023.
Author URL.
Stevens D, Oades PJ, Williams CA (2014). Airflow limitation following cardiopulmonary exercise testing and heavy-intensity intermittent exercise in children with cystic fibrosis.
European Journal of PediatricsAbstract:
Airflow limitation following cardiopulmonary exercise testing and heavy-intensity intermittent exercise in children with cystic fibrosis
The clinical importance of exercise testing and training in the healthcare management of young patients with cystic fibrosis (CF) is growing. The aim of the present study was to determine the incidence of airflow limitation following cardiopulmonary exercise testing (CPET) and heavy-intensity intermittent exercise (HIIE) in young patients with CF. Nineteen young patients with CF and respective paired-matched controls performed CPET and HIIE on separate days. Forced expiratory volume in one second (FEV1) was measured pre- and post each exercise modality. A fall in FEV1 of 10 % or greater was used to define airflow limitation. The incidence of airflow limitation was significantly greater in the CF group than in the controls following CPET (32 vs. 5 %; p = 0.03); however, no significant difference in the incidence of airflow limitation was shown following HIIE between the CF group and controls (11 vs. 16 %; p = 0.64).Conclusion: Our data show that the incidence of airflow limitation following CPET in young patients with CF is high. Therefore, clinicians may wish to identify whether young CF patients experience airflow limitation following strenuous exercise, such as CPET, before it is performed. However, HIIE carries a low risk for airflow limitation and may be prescribed as a safe, yet effective exercise modality for young patients with CF. © 2014 Springer-Verlag Berlin Heidelberg.
Abstract.
Oliver JL, De Ste Croix MBA, Lloyd RS, Williams CA (2014). Altered neuromuscular control of leg stiffness following soccer-specific exercise.
European Journal of Applied Physiology,
114(11), 2241-2249.
Abstract:
Altered neuromuscular control of leg stiffness following soccer-specific exercise
Purpose: to examine changes to neuromuscular control of leg stiffness following 42 min of soccer-specific exercise.
Abstract.
Oliver JL, De Ste Croix MBA, Lloyd RS, Williams CA (2014). Altered neuromuscular control of leg stiffness following soccer-specific exercise. European Journal of Applied Physiology
Williams CA, Saynor ZL, Tomlinson OW, Barker AR (2014). Cystic fibrosis and physiological responses to exercise.
Expert Rev Respir Med,
8(6), 751-762.
Abstract:
Cystic fibrosis and physiological responses to exercise.
Cardiopulmonary exercise testing is underutilized within the clinical management of patients with cystic fibrosis. But within the last 5 years, there has been considerable interest in its implementation, which has included deliberations by the European Cystic Fibrosis Society about incorporating this method within the clinical assessment of patients. This review examines the current use of cardiopulmonary exercise testing in assessing the extent and cause(s) of exercise limitation from a pediatric perspective. Examples of the measured parameters and their interpretation are provided. Critical synthesis of recent work in the oxygen uptake (VO2) kinetics response to and following exercise is also discussed, and although identified more as a research tool, its utilization advances researchers understanding of the cardiovascular, respiratory and muscular limitations to exercise tolerance. Finally, exercise and its application in therapeutic interventions are highlighted and a number of recommendations made about the utility of exercise prescription.
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Wu M-Y, Bowtell JL, Williams CA (2014). Glycaemic index of meals affects appetite sensation but not energy balance in active males.
Eur J Nutr,
53(1), 309-319.
Abstract:
Glycaemic index of meals affects appetite sensation but not energy balance in active males.
BACKGROUND: Foods with low glycaemic index (LGI) are reported to suppress appetite mainly in overweight population but have not been investigated in athletic adults. OBJECTIVE: the aim of this study was to compare the short-term effects of LGI and high GI (HGI) meals over a day on subsequent subjective appetite sensation, energy intake, energy expenditure, energy balance and resting metabolic rate in physically active males. METHODS: This cross-sectional randomized crossover study included 14 active males (mean ± SD; age 34.5 ± 8.9 years, body mass index 22.8 ± 2.1 kg m(-2)) to consume LGI and HGI meals on two separate days. On each trial day, participants consumed a breakfast in the laboratory and then left with a packed lunch, dinner and snacks. Appetite scores, energy intake and expenditure were assessed. RESULTS: the area under the curve for appetite scores of the HGI trial was significantly smaller than that of the LGI trial during the laboratory period (p = 0.027) and throughout the day (p = 0.009). No significant differences in energy intake, energy expenditure, energy balance and resting metabolic rate were found between groups, between the trial days and between the corresponding post-trial days. CONCLUSIONS: These results show that frequent ingestion of the HGI meals, contrary to the previous reports, suppresses appetite more than that of LGI meals, but did not affect energy balance in physically active normal-weight males.
Abstract.
Author URL.
Bendiksen M, Williams CA, Hornstrup T, Clausen H, Kloppenborg J, Shumikhin D, Brito J, Horton J, Barene S, Jackman SR, et al (2014). Heart rate response and fitness effects of various types of physical education for 8- to 9-year-old schoolchildren.
European Journal of Sport Science,
14(8), 861-869.
Abstract:
Heart rate response and fitness effects of various types of physical education for 8- to 9-year-old schoolchildren
Abstract: the present study investigated the heart rate (HR) response to various types of physical education (PE) activities for 8- to 9-year-olds (five school classes, n = 93) and the fitness effects of a short-term PE training programme (three of the five classes, n = 59) with high compared to low-to-moderate aerobic intensity. HR was recorded during small-sided indoor soccer (SO), basketball (BB), unihockey (UH), circuit training (CT), walking (W) and Nintendo Wii Boxing (NWB) and Nintendo Wii Tennis (NWT). Maximal HR (HRmax) and physical fitness was determined by the Yo-Yo Intermittent Recovery Level 1 Children's test (YYIR1C) test. Following cluster randomisation, three classes were tested before and after 6 wks with 2 × 30 min/wk SO and UH lessons [high-intensity (HI), 2 classes, n = 39] or low-to-moderate intensity PE lessons (CON, 1 class, n = 20). Average HR in SO (76 ± 1% HRmax), BA (77 ± 1% HRmax) and UH (74 ± 1% HRmax) was higher (P < 0.05) than in CT (62 ± 1% HRmax), W (57 ± 1% HRmax), NWB (65 ± 2% HRmax) and NWT (57 ± 1% HRmax). Time with HR > 80% and 90% HRmax, respectively, was higher (P < 0.05) in SO (42 ± 4 and 12 ± 2%), BB (41 ± 5 and 13 ± 3%) and UH (34 ± 3 and 9 ± 2%) than in CT, W and NW (0–5%), with time >80% HRmax being higher (P < 0.05) in SO than UH. After 6 wk, YYIR1C performance was increased (P < 0.05) by 22% in HI (673 ± 57 to 821 ± 71 m), but unaltered in CON (674 ± 88 to 568 ± 81 m). HR 2 min into YYIR1C was lowered (P < 0.05) in HI after 6 wks (92.4 ± 0.8 to 89.1 ± 0.9% HRmax), but not in CON. In conclusion, ball games elicited high aerobic loading for young schoolchildren and a short-term, low-volume ball game PE-intervention improved physical fitness. Traditional PE sessions had no effects on intermittent exercise performance.
Abstract.
Bendiksen M, Williams CA, Hornstrup T, Clausen H, Kloppenborg J, Shumikhin D, Brito J, Horton J, Barene S, Jackman SR, et al (2014). Heart rate response and fitness effects of various types of physical education for 8- to 9-year-old schoolchildren. European Journal of Sport Science
Saynor ZL, Barker AR, Oades PJ, Williams CA (2014). Impaired aerobic function in patients with cystic fibrosis during ramp exercise.
Med Sci Sports Exerc,
46(12), 2271-2278.
Abstract:
Impaired aerobic function in patients with cystic fibrosis during ramp exercise.
PURPOSE: This study aimed to document the matching of muscle O2 delivery to O2 use in young patients with cystic fibrosis (CF) from muscle deoxygenation (HHb) dynamics during ramp exercise. METHODS: Ten patients with stable, mild-to-moderate CF (12.7 ± 2.8 yr) and 10 healthy controls (CON, 12.8 ± 2.8 yr) completed a combined ramp and supramaximal cycling test to determine maximal O2 uptake (VËO2max). Changes in gas exchange and ventilation, HR, and m. vastus lateralis HHb (near-infrared spectroscopy) were assessed. Δ[HHb]-work rate and Δ[HHb]-VËO2 profiles were normalized and fit using a sigmoid function. RESULTS: Aerobic function was impaired in CF, indicated by very likely reduced fat-free mass-normalized VËO2max (mean difference, ±90% confidence interval: -7.9 mL·kg·min, ±6.1), very likely lower VËO2 gain (-1.44 mL·min·W, ±1.12), and a likely slower VËO2 mean response time (11 s, ±13). An unclear effect was found upon the absolute and relative work rate (-14 W, ±44, and -0.7% peak power output, ±12.0, respectively) and the absolute and percentage (-0.10 L·min, ±0.43, and 3.3% VËO2max, ±6.0) VËO2 corresponding to 50% Δ[HHb] amplitude, respectively, between groups. However, arterial oxygen saturation (SpO2) was very likely lower in CF (-1%, ±1) and demonstrated moderate-to-very large relations with parameters of aerobic function. CONCLUSIONS: Young patients with mild-to-moderate CF present with impaired aerobic function during ramp incremental cycling exercise. Because the rate of fractional O2 extraction during ramp cycling exercise was not altered by CF, yet SpO2 was lower, the present findings support the notion of centrally mediated oxygen delivery to principally limit the aerobic function of pediatric patients with CF during ramp incremental cycling exercise.
Abstract.
Author URL.
Breese BC, Barker AR, Armstrong N, Fulford J, Williams CA (2014). Influence of thigh activation on the VOâ slow component in boys and men.
Eur J Appl Physiol,
114(11), 2309-2319.
Abstract:
Influence of thigh activation on the VOâ slow component in boys and men.
PURPOSE: During constant work rate exercise above the lactate threshold (LT), the initial rapid phase of pulmonary oxygen uptake (VOâ) kinetics is supplemented by an additional VOâ slow component (VOâSc) which reduces the efficiency of muscular work. The VOâSc amplitude has been shown to increase with maturation but the mechanisms are poorly understood. We utilized the transverse relaxation time (Tâ) of muscle protons from magnetic resonance imaging (MRI) to test the hypothesis that a lower VOâ slow component (VOâSc) amplitude in children would be associated with a reduced muscle recruitment compared to adults. METHODS: Eight boys (mean age 11.4 ± 0.4) and eight men (mean age 25.3 ± 3.3 years) completed repeated step transitions of unloaded-to-very heavy-intensity (U → VH) exercise on a cycle ergometer. MRI scans of the thigh region were acquired at rest and after VH exercise up to the VOâSc time delay (ScTD) and after 6 min. Tâ for each of eight muscles was adjusted in relation to cross-sectional area and then summed to provide the area-weighted ΣTâ as an index of thigh recruitment. RESULTS: There were no child/adult differences in the relative VOâSc amplitude [Boys 14 ± 7 vs. Men 18 ± 3 %, P = 0.15, effect size (ES) = 0.8] during which the change (â) in area-weighted ΣTâ between the ScTD and 6 min was not different between groups (Boys 1.6 ± 1.2 vs. Men 2.3 ± 1.1 ms, P = 0.27, ES = 0.6). A positive and strong correlation was found between the relative VOâSc amplitude and the magnitude of the area-weighted âΣTâ in men (r = 0.92, P = 0.001) but not in boys (r = 0.09, P = 0.84). CONCLUSIONS: This study provides evidence to show that progressive muscle recruitment (as inferred from Tâ changes) contributes to the development of the VOâSc during intense submaximal exercise independent of age.
Abstract.
Author URL.
Breese BC, Barker AR, Armstrong N, Fulford J, Williams CA (2014). Influence of thigh activation on the [Formula Presented] O<inf>2</inf> slow component in boys and men.
European Journal of Applied Physiology,
114(11), 2309-2319.
Abstract:
Influence of thigh activation on the [Formula Presented] O2 slow component in boys and men
Purpose: During constant work rate exercise above the lactate threshold (LT), the initial rapid phase of pulmonary oxygen uptake ([Formula Presented]O2) kinetics is supplemented by an additional [Formula Presented]O2 slow component ([Formula Presented]O2Sc) which reduces the efficiency of muscular work. The [Formula Presented]O2Sc amplitude has been shown to increase with maturation but the mechanisms are poorly understood. We utilized the transverse relaxation time (T2) of muscle protons from magnetic resonance imaging (MRI) to test the hypothesis that a lower [Formula Presented]O2 slow component ([Formula Presented]O2Sc) amplitude in children would be associated with a reduced muscle recruitment compared to adults.
Abstract.
Breese BC, Barker AR, Armstrong N, Fulford J, Williams CA (2014). Influence of thigh muscle activation on pulmonary O2 uptake kinetics during very heavy intensity exercise in boys and men.
European Journal of Applied Physiology,
114, 2309-2319.
Abstract:
Influence of thigh muscle activation on pulmonary O2 uptake kinetics during very heavy intensity exercise in boys and men
During constant work rate exercise above the
lactate threshold (LT ), the initial rapid phase of pulmonary
oxygen uptake (ËV O2) kinetics is supplemented by an
additional ËV O2 slow component (ËV O2Sc) which reduces
the efficiency of muscular work. The ËV O2Sc amplitude has
been shown to increase with maturation but the mechanisms
are poorly understood. We utilized the transverse
relaxation time (T2) of muscle protons from magnetic resonance
imaging (MRI) to test the hypothesis that a lower
ËV
O2 slow component (ËV O2Sc) amplitude in children would
be associated with a reduced muscle recruitment compared
to adults.
Methods Eight boys (mean age 11.4 ± 0.4) and eight
men (mean age 25.3 ± 3.3 years) completed repeated step
transitions of unloaded-to-very heavy-intensity (U → VH)
exercise on a cycle ergometer. MRI scans of the thigh
region were acquired at rest and after VH exercise up to
the ËV O2Sc time delay (ScTD) and after 6 min. T2 for each of eight muscles was adjusted in relation to cross-sectional
area and then summed to provide the area-weighted ΣT2 as
an index of thigh recruitment.
Results T here were no child/adult differences in the relative
ËVO2Sc amplitude [Boys 14 ± 7 vs. Men 18 ± 3 %,
P = 0.15, effect size (ES) = 0.8] during which the change
(Δ) in area-weighted ΣT2 between the ScTD and 6 min
was not different between groups (Boys 1.6 ± 1.2 vs. Men
2.3 ± 1.1 ms, P = 0.27, ES = 0.6). A positive and strong
correlation was found between the relative ËV O2Sc amplitude
and the magnitude of the area-weighted ΔΣT2 in men
(r = 0.92, P = 0.001) but not in boys (r = 0.09, P = 0.84).
Conclusions T his study provides evidence to show
that progressive muscle recruitment (as inferred from T2
changes) contributes to the development of the ËV O2Sc during
intense submaximal exercise independent of age.
Abstract.
Willcocks RJ, Fulford J, Armstrong N, Barker AR, Williams CA (2014). Muscle metabolism during fatiguing isometric quadriceps exercise in adolescents and adults.
Appl Physiol Nutr Metab,
39(4), 439-445.
Abstract:
Muscle metabolism during fatiguing isometric quadriceps exercise in adolescents and adults.
Children and adolescents are less susceptible to muscle fatigue during repeated bouts of high-intensity exercise than adults, but the physiological basis for these differences is not clear. The purpose of the current investigation was to investigate the muscle metabolic responses, using 31-phosphorus magnetic resonance spectroscopy, during fatiguing isometric quadriceps exercise in 13 adolescents (7 females) and 14 adults (8 females). Participants completed 30 maximal voluntary contractions (6-s duration) separated by 6 s of rest. Fatigue was quantified as the relative decrease in force over the test. Fatigue was not significantly different with age (p = 0.20) or sex (p = 0.63). Metabolic perturbation (change in phosphocreatine, inorganic phosphate, and ADP concentrations) was significantly greater in adults compared with adolescents; no sex effects were present. Muscle pH did not differ with age or sex. Phosphocreatine recovery following exercise was not significantly different with age (p = 0.27) or sex (p = 0.97) but a significant interaction effect was present (p = 0.04). Recovery tended to be faster in boys than men but slower in girls than women, though no significant group differences were identified. The results of this study show that at a comparable level of muscle fatigue, the metabolic profile is profoundly different between adolescents and adults.
Abstract.
Author URL.
Pieles GE, Horn R, Williams CA, Stuart AG (2014). Paediatric exercise training in prevention and treatment.
Archives of Disease in Childhood,
99(4), 380-385.
Abstract:
Paediatric exercise training in prevention and treatment
Exercise training is an underused intervention in paediatric healthcare. This is surprising, since initial evidence demonstrates its effectiveness and safety; furthermore it confers socioeconomic benefits for healthcare systems. Pilot studies have assessed and confirmed the feasibility of exercise training in many paediatric disease settings. However, more research is needed to understand the pathophysiology, quantify treatment effects and monitor outcomes. A concerted effort from researchers, health professionals and police makers will be necessary to make exercise training an evidence-based and cost-effective intervention in paediatric care.
Abstract.
Saynor ZL, Barker AR, Oades PJ, Williams CA (2014). The effect of ivacaftor in adolescents with cystic fibrosis (G551D mutation): an exercise physiology perspective.
Pediatr Phys Ther,
26(4), 454-461.
Abstract:
The effect of ivacaftor in adolescents with cystic fibrosis (G551D mutation): an exercise physiology perspective.
PURPOSE: the purpose of this report was to evaluate the influence of 12 weeks of ivacaftor treatment on the aerobic function of 2 teenage patients with cystic fibrosis (CF; ΔF508/G551D) using a maximal cardiopulmonary exercise test. SUMMARY OF KEY POINTS: One patient, with relatively mild disease, demonstrated no clinically meaningful changes in maximal oxygen uptake ((Equation is included in full-text article.)O2max). However, in the second case, with more established lung disease on imaging, (Equation is included in full-text article.)O2max improved by approximately 30%, an improvement out of proportion with early lung function changes. This improvement resulted from increased muscle oxygen delivery and extraction. STATEMENT OF CONCLUSIONS: Cardiopulmonary exercise testing can monitor the extent and cause(s) of change following interventions such as ivacaftor, with the potential to identify functional changes independent from spirometry indices. RECOMMENDATIONS FOR CLINICAL PRACTICE: Cardiopulmonary exercise testing represents an important and comprehensive clinical assessment tool, and its use as an outcome measure in the functional assessment of patients with CF is encouraged.
Abstract.
Author URL.
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.
Abstract.
Author URL.
Barker AR, Day J, Smith A, Bond B, Williams CA (2014). The influence of 2 weeks of low-volume high-intensity interval training on health outcomes in adolescent boys.
J Sports Sci,
32(8), 757-765.
Abstract:
The influence of 2 weeks of low-volume high-intensity interval training on health outcomes in adolescent boys.
The present study aimed to establish whether 2 weeks of high-intensity interval training would have a beneficial effect on aerobic fitness, fat oxidation, blood pressure and body mass index (BMI) in healthy adolescent boys. Ten adolescent boys (15.1 ± 0.3 years, 1.3 ± 0.2 years post-estimated peak height velocity) completed six sessions of Wingate-style high-intensity interval training over a 2-week period. The first session consisted of four sprints with training progressed to seven sprints in the final session. High-intensity interval training had a beneficial effect on maximal O2 uptake (mean change, ±90% confidence intervals: 0.19 L · min(-1), ±0.19, respectively), on the O2 uptake at the gas exchange threshold (0.09 L · min(-1), ±0.13) and on the O2 cost of sub-maximal exercise (-0.04 L · min(-1), ±0.04). A beneficial effect on the contribution of lipid (0.06 g · min(-1), ±0.06) and carbohydrate (-0.23 g · min(-1), ±0.14) oxidation was observed during sub-maximal exercise, but not for the maximal rate of fat oxidation (0.04 g · min(-1), ±0.08). Systolic blood pressure (1 mmHg, ±4) and BMI (0.1 kg · m2, ±0.1) were not altered following training. These data demonstrate that meaningful changes in health outcomes are possible in healthy adolescent boys after just six sessions of high-intensity interval training over a 2-week period.
Abstract.
Author URL.
Willcocks RJ, Fulford J, Barker AR, Armstrong N, Williams CA (2014). Two protocols to measure mitochondrial capacity in women and adolescent girls: a 31P-MRS preliminary study.
Pediatr Exerc Sci,
26(2), 210-217.
Abstract:
Two protocols to measure mitochondrial capacity in women and adolescent girls: a 31P-MRS preliminary study.
The phosphocreatine (PCr) recovery time constant (τ) following exercise provides a measure of mitochondrial oxidative capacity. The purpose of this investigation was to use 2 different protocols to determine τ in adolescent females. 31P-MR spectra were collected during 2 exercise tests in 6 adolescent girls (13.8 ± 0.3 y) and 7 women (23.2 ± 3.4 y). The first test consisted of 23 repeated 4 seconds maximal isometric calf contractions separated by 12-second recovery; PCr recovery between the final 18 contractions was used to calculate τ. The second test was a sustained 20-second maximal contraction; recovery was fitted with an exponential function to measure τ. PCr τ did not significantly differ between groups: (gated exercise: 4 girls: 16 ± 5 s, 7 women: 17 ± 5 s, p; sustained exercise: 6 girls: 19 ± 6 s, 7 women: 19 ± 4 s). Bland-Altman analysis demonstrated a close agreement between sustained and gated exercise. Both gated and sustained exercise appear feasible in a pediatric population, and offer a noninvasive evaluation of mitochondrial oxidative capacity.
Abstract.
Author URL.
Pieles GE, Szantho G, Rodrigues JCL, Lawton CB, Williams CA, Stuart AG, Tulloh RMR, Hamilton MCK (2014). Use of phase-contrast magnetic resonance angiography to measure adaptations of aortic and pulmonary artery flow during supine aerobic exercise.
LANCET,
383, 80-80.
Author URL.
Lambrick DM, Westrupp N, Williams CA, Faulkner JA (2013). A comparison of exercise economy between obese and non-obese 8 to 10-year old children. Obesity Research & Clinical Practice, 7, e22-e23.
Saynor ZL, Barker AR, Oades PJ, Williams CA (2013). A protocol to determine valid VËO2max in young cystic fibrosis patients.
J Sci Med Sport,
16(6), 539-544.
Abstract:
A protocol to determine valid VËO2max in young cystic fibrosis patients.
OBJECTIVES: Measuring aerobic fitness (VËO2max) via a maximal cardiopulmonary exercise test is an important clinical tool in cystic fibrosis. This study sought to establish: (1) the validity of traditional criteria to verify maximal efforts during a ramp cardiopulmonary exercise test; and (2) whether VËO2 measured during an exhaustive cardiopulmonary exercise test represents a valid VËO2max in paediatric patients, using a subsequent exhaustive supramaximal (Smax) exercise test. DESIGN: Cross-sectional. METHODS: Fourteen patients (7-18 years; 10 males) completed an exhaustive ramp test to determine VËO2max. Following 15-min recovery, Smax (110% ramp peak power output) was performed. RESULTS: Ramp test VËO2peak was significantly higher than VËO2 documented at traditional endpoint criteria, including a RER of 1.00 (0.99±0.47 L min(-1) vs. 1.83±0.78 L min(-1), p
Abstract.
Author URL.
Saynor ZL, Barker AR, Oades PJ, Williams CA (2013). A protocol to determine valid VÌO2max in young cystic fibrosis patients.
Journal of Science and Medicine in Sport,
16(6), 539-544.
Abstract:
A protocol to determine valid VÌO2max in young cystic fibrosis patients
Objectives: Measuring aerobic fitness (VÌO2max) via a maximal cardiopulmonary exercise test is an important clinical tool in cystic fibrosis. This study sought to establish: (1) the validity of traditional criteria to verify maximal efforts during a ramp cardiopulmonary exercise test; and (2) whether VÌO2 measured during an exhaustive cardiopulmonary exercise test represents a valid VÌO2max in paediatric patients, using a subsequent exhaustive supramaximal (Smax) exercise test. Design: Cross-sectional. Methods: Fourteen patients (7-18 years; 10 males) completed an exhaustive ramp test to determine VÌO2max. Following 15-min recovery, Smax (110% ramp peak power output) was performed. Results: Ramp test VÌO2peak was significantly higher than VÌO2 documented at traditional endpoint criteria, including a RER of 1.00 (0.99±0.47Lmin-1 vs. 1.83±0.78Lmin-1, p
Abstract.
Varley J, Moore M, Williams CA (2013). Acute energy intake and appetite responses following high-intensity interval exercise in 12-13 year old boys and girls.
PROCEEDINGS OF THE NUTRITION SOCIETY,
72(OCE3), E151-E151.
Author URL.
Armstrong N (2013). Aerobic fitness and physical activity in children.
Pediatr Exerc Sci,
25(4), 548-560.
Abstract:
Aerobic fitness and physical activity in children.
In Volume 1 of Pediatric Exercise Science (PES), a paper by Fenster et al. (25) investigated the relationship between peak oxygen uptake (peak VO2) and physical activity (PA) in 6- to 8-year-old children. They used both questionnaires and large-scale integrated activity monitors (LSIs) to estimate daily PA and determined peak VO2 using an incremental treadmill test to volitional exhaustion. They concluded that peak VO2 correlated well with PA as measured by LSIs but commented that questionnaire data were only weakly and nonsignificantly associated with LSI and peak VO2 data. Peak VO2 and PA are the most researched and reported variables in the 25-year history of PES. Yet, the assessment and interpretation of young people's aerobic fitness and PA remain problematic and any meaningful relationship between them during childhood and adolescence is shrouded with controversy. The present paper uses Fenster et al.'s (25) report as an indicator of where we were 25 years ago, outlines how far we have advanced since then, and suggests future directions of research in the study of aerobic fitness and PA. In the first volume of PES, Fenster, Freedson, Washburn, and Ellison (25) investigated the relationship between 6- to 8-year-old children's peak oxygen uptake (peak VO2) and physical activity (PA). Five boys and 13 girls participated in the study and their data were pooled for analysis. Peak VO2 was determined during an incremental treadmill test to voluntary exhaustion and PA was estimated using both questionnaires and large-scale integrated activity monitors (LSIs). On the basis of a significant interclass correlation coefficient of r =. 59 between peak VO2 and the log of LSI average counts per hour Fenster et al. (25) concluded that "aerobic capacity, as measured by peak VO2 correlated well with physical activity as measured by LSI" (p.134). They also commented that questionnaire data were only weakly and nonsignificantly associated with LSI and peak VO2 data. Young people's peak VO2 and PA are the most researched and reported variables in the 25-year history of PES and yet the assessment and interpretation of peak VO2 and PA and any meaningful relationship between them during growth and maturation are still shrouded with controversy. The present paper uses Fenster et al.'s (25) work as an indicator of our understanding of young people's peak VO2 and PA in 1989, briefly reviews what we know in 2013, and suggests future directions of research.
Abstract.
Author URL.
Westendorf ML, Puduri V, Williams CA, Joshua T, Govindasamy R (2013). Dietary and manure management practices on equine farms in two new jersey watersheds.
Journal of Equine Veterinary Science,
33(8), 601-606.
Abstract:
Dietary and manure management practices on equine farms in two new jersey watersheds
Equine farms are increasing in number in Northeast and Mid-Atlantic states. These farms may influence environmental quality owing to manure collection, storage, spreading, and disposal practices. A manure management survey was mailed to 700 New Jersey equine farms during the winter of 2009-2010 (these farms were located in two watersheds). Two hundred forty-two surveys were returned; 10% were training or performance farms, whereas the remainder (90%) were breeding, boarding, or pleasure farms. There were differences between the two watersheds in turnout time, pasture acreage, use of drag harrows, and income. Respondents answered questions about diet and environmental management on farms. Seventy-eight percent had bunk management plans. Forty-seven percent disposed of waste feed in a manure pile, 35% left it on fields or paddocks, and 18% put it in a dumpster. Twenty-six percent engage a professional for feeding advice (21% veterinarians, 2% extension, 3% nutrition consultants). Most respondents did not have a regular feed management plan. Sixty-two percent of all farms spread manure on-farm. of those who spread, 29% have >8.09 hectares (20 acres) for spreading. Ninety-six percent of respondents stored manure >100 ft from water or wetlands. Comparison of cross-tabulations indicates a strong relationship (P
Abstract.
Patikas D, Kansizoglou A, Koutlianos N, Williams CA, Hatzikotoulas K, Bassa E, Kotzamanidis C (2013). Fatigue and recovery in children and adults during sustained contractions at 2 different submaximal intensities.
Applied Physiology, Nutrition and Metabolism,
38(9), 953-959.
Abstract:
Fatigue and recovery in children and adults during sustained contractions at 2 different submaximal intensities
The purpose of this study was to examine the effects of submaximal sustained contractions on fatigue and recovery properties in untrained prepubescent boys (n = 14) and men (n = 14). All participants performed, in random order, an isometric plantar flexion at 20% and 60% of their maximal voluntary contraction (MVC) until exhaustion (20%fatigue and 60%fatigue, respectively). During both fatigue protocols, surface electromyogram (sEMG) of the soleus and tibialis anterior muscles was recorded. Before and after the fatigue protocol, MVCs and blood lactate concentration were obtained. During 20%fatigue and 60%fatigue, agonist and antagonist sEMG increased gradually to a similar extent in both groups. Immediately after fatigue, MVC torque decreased in both groups, compared with prefatigue values, and boys recovered faster than men in both fatigue protocols. The reduction in agonist sEMG during MVC after fatigue was not significantly different between men and boys (p < 0.05), independent of the fatigue protocol. sEMG of boys recovered to baseline values 3 min after the 20%fatigue and 60%fatigue protocols, whereas men did not recover. Lactate concentration increased immediately after the end of the fatigue protocols, compared with the prefatigue values (p < 0.05). This increase was higher for the 60%fatigue than for 20%fatigue protocol, and did not differ between boys and men. It is concluded that low- and middle-intensity submaximal sustained isometric fatigue protocols induce similar fatigue effects in boys and men. Furthermore, it was shown that boys can recover faster than men, independent of the contraction intensity that induces fatigue.
Abstract.
Pieles GE, Horn R, Williams CA, Stuart AG (2013). Paediatric exercise training in prevention and treatment. Archives of Disease in Childhood
Williams CA, Stevens D (2013). Physical activity and exercise training in young people with cystic fibrosis: Current recommendations and evidence.
JOURNAL OF SPORT AND HEALTH SCIENCE,
2(1), 39-46.
Author URL.
Birrer D, Lienhard D, Williams CA, Röthlin P, Morgan G (2013). Prevalence of non-functional overreaching and the overtraining syndrome in Swiss elite athletes.
Schweizerische Zeitschrift fur Sportmedizin und Sporttraumatologie,
61(4), 23-29.
Abstract:
Prevalence of non-functional overreaching and the overtraining syndrome in Swiss elite athletes
Objectives: Fatigue and unaccountable underperformance are common for athletes, but there is a lack of empirical data regarding the prevalence of non-functional overreaching (NFOR) and the overtraining syndrome (OTS). Using the overtraining definition of the European College of Sport Science (ECSS), the present study aimed to explore the prevalence, symptoms and associated factors of NFOR/OTS across Swiss elite athletes in various sports. Method: 139 Swiss elite athletes (63 males and 76 females, Mage = 23.6, SD age = 5.6 y) from 26 different sports completed al 7-item online survey about underperformance and symptoms of NFOR/OTS. 95% of the sample represented Switzerland in their sport. Athletes were classified as NFOR/OTS by according to the overtraining definition of the ECSS. Data were analysed using Mann-Whitney U nonparametric tests and ANOVAs. Results: 9% of the athletes were classified as OTS and 21% as NFOR at least once in their career. The prevalence was significantly higher in medium-physical demand sports than in low-physical demand sports (p -.02). There were no significant differences in the NFOR/OTS prevalence between individual and team sports and female and male athletes. Competition level and training load had also no significant influence on the NFOR/OTS prevalence, although low-physical demand sports trained significantly less than medium- and high-physical demand sports. Injury/illness, loss of weight and sleep disturbance rates were significantly higher in the NFOR/OTS group. More than 70% of the NFOR/OTS athletes reported loss of motivation and emotional disturbances. Conclusions: the NFOR/OTS career prevalence rate of Swiss elite athletes can be estimated at approximately 30%. NFOR/OTS is accompanied by biopsychosocial signs of maladjustment, e.g. emotional disturbances, loss of motivation, sleep disturbances, injury/illness and weight loss, but training load is not a predictor of NFOR/OTS.
Abstract.
Bott RC, Greene EA, Koch K, Martinson KL, Siciliano PD, Williams C, Trottier NL, Burk A, Swinker A (2013). Production and environmental implications of equine grazing.
Journal of Equine Veterinary Science,
33(12), 1031-1043.
Abstract:
Production and environmental implications of equine grazing
Horses' physical and digestive well-being is often enhanced when allowed to graze on pastures. Furthermore, a well-managed pasture can contribute to economic viability. Grazing can however have deleterious effects on the environment if not properly managed. Although equine grazing, defecating, and ground trampling behavior is unique from that of other livestock species, pasture management practices are often based on those derived from cattle grazing. This review summarizes the current knowledge of impacts of equine grazing on pasture quality and environment and identifies gaps where further information is needed to formulate and recommend sustainable grazing methods specific to equine. © 2013.
Abstract.
Saynor ZL, Barker AR, Oades PJ, Williams CA (2013). Reproducibility of maximal cardiopulmonary exercise testing for young cystic fibrosis patients.
Journal of Cystic Fibrosis,
12(6), 644-650.
Abstract:
Reproducibility of maximal cardiopulmonary exercise testing for young cystic fibrosis patients
Background: the reproducibility of cardiopulmonary exercise testing (CPET) has not been established in young cystic fibrosis (CF) patients using a valid protocol. Methods: Thirteen 7-18. year olds completed three CPETs, separated by 48. h and 4-6. weeks. CPET involved a ramp-incremental cycling test with supramaximal verification. Results: Maximal oxygen uptake was repeatedly determined with no learning effect and typical errors expressed as a coefficient of variation (TECV%) of 9.3% (48h) and 13.3% (4-6weeks). The reproducibility of additional parameters of aerobic function [gas exchange threshold (TECV%: 11.2%, 16.8%); VO2 mean response time (TECV%: 37.8%, 89.4%); VO2 gain (TECV%: 17.4%, 24.5%)] and clinical utility [e.g. SaO2% (TECV%: 2.2%, 3.1%); ventilatory drive (VE/VCO2-slope) (TECV%: 7.8%, 17.7%)] was also established over the short- and the medium-term, respectively. Conclusion: These results establish limits of variability to determine meaningful changes over the short- and the medium-term for CPET outcomes in young CF patients. © 2013 European Cystic Fibrosis Society.
Abstract.
Saynor ZL, Barker AR, Oades PJ, Williams CA (2013). Reproducibility of maximal cardiopulmonary exercise testing for young cystic fibrosis patients.
J Cyst Fibros,
12(6), 644-650.
Abstract:
Reproducibility of maximal cardiopulmonary exercise testing for young cystic fibrosis patients.
BACKGROUND: the reproducibility of cardiopulmonary exercise testing (CPET) has not been established in young cystic fibrosis (CF) patients using a valid protocol. METHODS: Thirteen 7-18 year olds completed three CPETs, separated by 48 h and 4-6 weeks. CPET involved a ramp-incremental cycling test with supramaximal verification. RESULTS: Maximal oxygen uptake was repeatedly determined with no learning effect and typical errors expressed as a coefficient of variation (TE(CV%)) of 9.3% (48 h) and 13.3% (4-6 weeks). The reproducibility of additional parameters of aerobic function [gas exchange threshold (TE(CV%): 11.2%, 16.8%); VO2 mean response time (TE(CV%): 37.8%, 89.4%); VO2 gain (TE(CV%): 17.4%, 24.5%)] and clinical utility [e.g. SaO2% (TE(CV%): 2.2%, 3.1%); ventilatory drive (V(E)/VCO2-slope) (TE(CV%): 7.8%, 17.7%)] was also established over the short- and the medium-term, respectively. CONCLUSION: These results establish limits of variability to determine meaningful changes over the short- and the medium-term for CPET outcomes in young CF patients.
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Author URL.
Malina RM, Baxter-Jones ADG, Armstrong N, Beunen GP, Caine D, Daly RM, Lewis RD, Rogol AD, Russell K (2013). Role of intensive training in the growth and maturation of artistic gymnasts.
Sports Medicine,
43(9), 783-802.
Abstract:
Role of intensive training in the growth and maturation of artistic gymnasts
Short stature and later maturation of youth artistic gymnasts are often attributed to the effects of intensive training from a young age. Given limitations of available data, inadequate specification of training, failure to consider other factors affecting growth and maturation, and failure to address epidemiological criteria for causality, it has not been possible thus far to establish cause-effect relationships between training and the growth and maturation of young artistic gymnasts. In response to this ongoing debate, the Scientific Commission of the International Gymnastics Federation (FIG) convened a committee to review the current literature and address four questions: (1) is there a negative effect of training on attained adult stature? (2) is there a negative effect of training on growth of body segments? (3) Does training attenuate pubertal growth and maturation, specifically, the rate of growth and/or the timing and tempo of maturation? (4) Does training negatively influence the endocrine system, specifically hormones related to growth and pubertal maturation? the basic information for the review was derived from the active involvement of committee members in research on normal variation and clinical aspects of growth and maturation, and on the growth and maturation of artistic gymnasts and other youth athletes. The committee was thus thoroughly familiar with the literature on growth and maturation in general and of gymnasts and young athletes. Relevant data were more available for females than males. Youth who persisted in the sport were a highly select sample, who tended to be shorter for chronological age but who had appropriate weight-for-height. Data for secondary sex characteristics, skeletal age and age at peak height velocity indicated later maturation, but the maturity status of gymnasts overlapped the normal range of variability observed in the general population. Gymnasts as a group demonstrated a pattern of growth and maturation similar to that observed among short-, normal-, late-maturing individuals who were not athletes. Evidence for endocrine changes in gymnasts was inadequate for inferences relative to potential training effects. Allowing for noted limitations, the following conclusions were deemed acceptable: (1) Adult height or near adult height of female and male artistic gymnasts is not compromised by intensive gymnastics training. (2) Gymnastics training does not appear to attenuate growth of upper (sitting height) or lower (legs) body segment lengths. (3) Gymnastics training does not appear to attenuate pubertal growth and maturation, neither rate of growth nor the timing and tempo of the growth spurt. (4) Available data are inadequate to address the issue of intensive gymnastics training and alterations within the endocrine system. © 2013 the Author(s).
Abstract.
Gracia-Marco L, Ortega FB, Ruiz JR, Williams CA, Hagströmer M, Manios Y, Kafatos A, Béghin L, Polito A, De Henauw S, et al (2013). Seasonal variation in physical activity and sedentary time in different European regions. The HELENA study.
Journal of Sports Sciences,
31(16), 1831-1840.
Abstract:
Seasonal variation in physical activity and sedentary time in different European regions. The HELENA study
This report aims (1) to examine the association between seasonality and physical activity (PA) and sedentary time in European adolescents and (2) to investigate whether this association was influenced by geographical location (Central-North versus South of Europe), which implies more or less extreme weather and daylight hours. Valid data on PA, sedentary time and seasonality were obtained in 2173 adolescents (1175 females; 12.5-17.5 years) included in this study. Physical activity and sedentary time were measured by accelerometers. ANCOVA was conducted to analyse the differences in PA and sedentary time across seasons. Results showed that girls had lower levels of moderate to vigorous PA (MVPA) and average PA, and spent more time in sedentary activities in winter compared with spring (all P < 0.05). Stratified analyses showed differences in PA and sedentary time between winter and spring in European girls from Central-North of Europe (P < 0.05 for sedentary time). There were no differences between PA and sedentary time across seasonality in boys. In conclusion, winter is related with less time spent in MVPA, lower average PA and higher time spent in sedentary activities in European adolescent girls, compared with spring. These differences seem to mainly occur in Central-North Europe. © 2013 Taylor & Francis.
Abstract.
Gracia-Marco L, Ortega FB, Ruiz JR, Williams CA, Hagströmer M, Manios Y, Kafatos A, Béghin L, Polito A, De Henauw S, et al (2013). Seasonal variation in physical activity and sedentary time in different European regions. The HELENA study.
J Sports Sci,
31(16), 1831-1840.
Abstract:
Seasonal variation in physical activity and sedentary time in different European regions. The HELENA study.
This report aims (1) to examine the association between seasonality and physical activity (PA) and sedentary time in European adolescents and (2) to investigate whether this association was influenced by geographical location (Central-North versus South of Europe), which implies more or less extreme weather and daylight hours. Valid data on PA, sedentary time and seasonality were obtained in 2173 adolescents (1175 females; 12.5-17.5 years) included in this study. Physical activity and sedentary time were measured by accelerometers. ANCOVA was conducted to analyse the differences in PA and sedentary time across seasons. Results showed that girls had lower levels of moderate to vigorous PA (MVPA) and average PA, and spent more time in sedentary activities in winter compared with spring (all P < 0.05). Stratified analyses showed differences in PA and sedentary time between winter and spring in European girls from Central-North of Europe (P < 0.05 for sedentary time). There were no differences between PA and sedentary time across seasonality in boys. In conclusion, winter is related with less time spent in MVPA, lower average PA and higher time spent in sedentary activities in European adolescent girls, compared with spring. These differences seem to mainly occur in Central-North Europe.
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Williams AJ, Henley WE, Williams CA, Hurst AJ, Logan S, Wyatt KM (2013). Systematic review and meta-analysis of the association between childhood overweight and obesity and primary school diet and physical activity policies. International Journal of Behavioural Nutrition and Physical Activity, 10
McGawley K, Leclair E, Dekerle J, Carter H, Williams CA (2012). A Test to Assess Aerobic and Anaerobic Parameters During Maximal Exercise in Young Girls.
PEDIATRIC EXERCISE SCIENCE,
24(2), 262-274.
Author URL.
Williams AJ, Wyatt KM, Hurst AJ, Williams CA (2012). A systematic review of associations between the primary school built environment and childhood overweight and obesity.
HEALTH & PLACE,
18(3), 504-514.
Author URL.
Lloyd RS, Oliver JL, Hughes MG, Williams CA (2012). Age-related differences in the neural regulation of stretch-shortening cycle activities in male youths during maximal and sub-maximal hopping.
Journal of Electromyography and Kinesiology,
22(1), 37-43.
Abstract:
Age-related differences in the neural regulation of stretch-shortening cycle activities in male youths during maximal and sub-maximal hopping
The aim of the current study was to investigate potential age-related differences in neural regulation strategies during maximal and sub-maximal hopping. Thirty-two boys from three different age groups (9-, 12- and 15-years), completed trials of both maximal and sub maximal hopping, and based on contact and flight times, measures of reactive strength index (RSI = jump height/contact time) and leg stiffness (peak ground reaction force/peak displacement of centre of mass) were collected respectively. During all trials, surface electromyograms (EMG) were recorded from four different muscle sites of the dominant lower limb, during 100. ms pre-ground contact, and then four subsequent stretch reflex phases: background muscle activity (0-30. ms), short-latency stretch reflex (31-60. ms), intermediate15 latency stretch reflex 61-90. ms and long-latency stretch reflex (91-120. ms). Reactive strength index and leg stiffness were measured during the hopping trials. During maximal hopping, both 12- and 15-year olds produced significantly greater RSI (P< 0.02) than 9-year olds, with 15-year olds utilising significantly greater soleus muscle activity during the 100. ms prior to ground contact than the younger age groups (P< 0.01). During sub-maximal hopping, 15-year olds produced significantly greater absolute leg stiffness than both 12- and 9-year olds (P< 0.01), with 9-year olds producing significantly less soleus muscle activity during the 31-60. ms time phase. For all age groups, sub-maximal hopping was associated with significantly greater background muscle activity and short-latency stretch reflex activity in the soleus and vastus lateralis, when compared to maximal hopping (P< 0.001). Results suggest that as children mature, they become more reliant on supra-spinal feed forward input and short latency stretch reflexes to regulate greater levels of leg stiffness and RSI when hopping. © 2011 Elsevier Ltd.
Abstract.
Williams CA, Burk AO (2012). Antioxidant status in elite three-day event horses during competition.
Oxidative Medicine and Cellular LongevityAbstract:
Antioxidant status in elite three-day event horses during competition
The objective of this study was to determine if competition intensity would have an effect on antioxidant status in horses before and during a three-day event. Body weight, body condition score, and blood was sampled from CCI2(*) (n=19) and CCI3(*) (n=23) horses before the start of dressage, 20 to 30min following cross-country, and 18-24h after cross-county. Data were analyzed using a PROC MIXED in SAS. There were no differences between CCI2(*) and CCI3(*) horses during competition for plasma cortisol, lactate, -tocopherol, retinol, or erythrocyte glutathione peroxidase. After cross-country, CCI3(*) horses had higher serum creatine kinase (P=0.003) and aspartate aminotransferase (P
Abstract.
Lamprecht ED, Williams CA (2012). Biomarkers of antioxidant status, inflammation, and cartilage metabolism are affected by acute intense exercise but not superoxide dismutase supplementation in horses.
Oxidative Medicine and Cellular LongevityAbstract:
Biomarkers of antioxidant status, inflammation, and cartilage metabolism are affected by acute intense exercise but not superoxide dismutase supplementation in horses
Objectives were to evaluate effects of (1) repetitive arthrocentesis on biomarkers of inflammation (prostaglandin E2, PGE2) and aggrecan synthesis (chondroitin sulfate-846; CS) in synovial fluid (SF); (2) exercise and superoxide dismutase (SOD) supplementation on biomarkers of inflammation, antioxidant status, and aggrecan synthesis, in horses. Preliminary trial. Standardbreds underwent four arthrocentesis procedures within 48 h and exhibited elevated CS and no changes in PGE2. Exercise trial. this randomized crossover design used twelve Standardbred mares which received either treatment (3000 IU d-1 oral SOD powder) or placebo (cellulose powder) for 6 wks which culminated with them running a repeated sprint exercise test (RSET). Samples were collected before (PRE), during (PEAK), and following exercise (POST). Exercise resulted in increased (P 0.05) antioxidant defenses including erythrocyte SOD, total glutathione, glutathione peroxidase, gene transcripts for interferon-gamma, interleukin-10, and interleukin-1β in blood, and decreased plasma nitric oxide. Exercise increased (P 0.05) SF CS and adjusted-PGE2, and higher (P 0.05) CS and PGE2 were found in hock versus carpus joints. No treatment effects were detected. Results suggest normal adaptive responses likely due to exercise-induced tissue microdamage and oxidative stress. Additional research is needed to identify benefit(s) of SOD supplementation in horses. © 2012 Emily D. Lamprecht and Carey A. Williams.
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Musa DI, Williams CA (2012). Cardiorespiratory fitness, fatness, and blood pressure associations in Nigerian youth.
Med Sci Sports Exerc,
44(10), 1978-1985.
Abstract:
Cardiorespiratory fitness, fatness, and blood pressure associations in Nigerian youth.
PURPOSE: This study aimed to examine the independent associations of cardiorespiratory fitness (CRF) and body fatness with resting blood pressure (BP) in children (9-11 yr) and adolescents (12-15 yr) in Benue State of Nigeria. METHODS: a total of 3243 children (n = 1017) and adolescents (n = 2226) were evaluated for aerobic fitness, body fatness, resting preexercise BP and recovery BP at minutes 1, 5, and 10 after a progressive aerobic cardiovascular endurance run test. Regression models, controlling for age and recovery BP at 1, 5, and 10 min after the progressive aerobic cardiovascular endurance run, determined the associations of independent variables with the dependent variables. RESULTS: Fatness and fitness were independent predictors of resting BP among participants, and the relationship of fatness with BP was more robust in adolescents than in children. In all cases, the relationships were stronger in boys than in girls. Combined fitness and fatness in predicting BP was modest (R(2) = 1%-3%) after controlling for age and postexercise BP. Postexercise BP was a major determinant of resting BP in both groups (R(2) = 23%-93%). In adolescents, fatter boys had 1.9 times likelihood of systolic HTN compared with leaner peers. Systolic and diastolic BP scores varied by fit-fat groups, the fit-low-fat group demonstrated the most favorable BP profiles, whereas the unfit-high-fat group showed the most adverse profiles. CONCLUSIONS: Irrespective of fatness, participants with higher CRF had more favorable BP profiles compared with their fat-unfit peers.
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Barker AR, Bond B, Toman C, Williams CA, Armstrong N (2012). Critical power in adolescents: physiological bases and assessment using all-out exercise.
Eur J Appl Physiol,
112(4), 1359-1370.
Abstract:
Critical power in adolescents: physiological bases and assessment using all-out exercise.
This study examined whether critical power (CP) in adolescents: (1) provides a landmark for maximal steady-state exercise; and (2) can be determined using 'all-out' exercise. Nine active 14-15 year olds (6 females, 3 males) performed five cycling tests: (1) a ramp test to determine VO(2peak); (2) up to four constant power output tests to determine CP; (3-4) constant power output exercise 10% above and 10% below CP; and (5) a 3 min all-out cycle test to establish the end power (EP) at 90 and 180 s of exercise. All participants completed 30 min of exercise below CP and were characterized by steady-state blood lactate and VO(2) profiles. In contrast, time to exhaustion during exercise above CP was 15.0 ± 7.0 min and characterized by an inexorable rise in blood lactate and a rise, stabilization (~91% VO(2peak)) and fall in VO(2) (~82% VO(2peak)) prior to exhaustion. Eight out of nine participants completed the 3 min test and their EPs at 90 s (148 ± 29 W) and 180 s (146 ± 30 W) were not different from CP (146 ± 27 W) (P = 0.98). The typical error of estimates for establishing CP using EP at 90 s or 180 s of the 3 min test were 25 W (19.7% CV) and 25 W (19.6% CV), respectively. CP in active adolescence provides a valid landmark for maximal steady-state exercise, although its estimation on an individual level using the 3 min all-out test may be of limited value. VO(2peak)
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Komar S, Miskewitz R, Westendorf M, Williams CA (2012). Effects of bedding type on compost quality of equine stall waste: Implications for small horse farms.
Journal of Animal Science,
90(3), 1069-1075.
Abstract:
Effects of bedding type on compost quality of equine stall waste: Implications for small horse farms
Our objective in this study is to compare 4 of the most common bedding materials used by equine operations on the chemical and physical characteristics of composted equine stall waste. Twelve Standardbred horses were adapted to the barn and surrounding environment for 2 wk before the start of the study. Groups of 3 horses were bedded on 1 of 4 different bedding types (wood shavings, pelletized wood materials, long straw, and pelletized straw) for 16 h per day for 18 d. Stalls were cleaned by trained staff daily, and all contents removed were weighed and stored separately by bedding material on a level covered concrete pad for the duration of the study. Compost piles were constructed using 3 replicate piles of each bedding type in a randomized complete block design. Each pile was equipped with a temperature sensor and data logger. Water was added and piles were turned weekly throughout the 100-d compost process. Initial and final samples were taken, dried, and analyzed for DM mass, OM, inorganic nitrogen (nitrate-N and ammonium-N), electrical conductivity, and soluble (plant-available) nutrients. Data were analyzed using the GLM procedure, and means were separated using Fischer's protected LSD test (P < 0.05). No significant temperature differences were observed among the bedding materials. The composting process resulted in significant reductions (P < 0.05) in DM mass for each of the 4 bedding materials. The composting process resulted in significant reductions (P < 0.05) in OM and C:N ratio for all 4 bedding materials. The composted long straw material had greater concentrations of total Kjeldahl nitrogen (P < 0.05), nitrate-N (P < 0.05), and ammonium-N (P < 0.05) than the composted wood shavings. This study demonstrated that incorporating a simple aerobic composting system may greatly reduce the overall volume of manure and yield a material that is beneficial for land application in pasture-based systems. The strawbased materials may be better suited for composting and subsequent land application; however, factors such as suitability of the bedding material for equine use, material cost, labor, and availability must be considered when selecting a bedding material. © 2012 American Society of Animal Science. All rights reserved.
Abstract.
Nimmerichter A, Eston R, Bachl N, Williams C (2012). Effects of low and high cadence interval training on power output in flat and uphill cycling time-trials.
Eur J Appl Physiol,
112(1), 69-78.
Abstract:
Effects of low and high cadence interval training on power output in flat and uphill cycling time-trials.
This study tested the effects of low-cadence (60 rev min(-1)) uphill (Int(60)) or high-cadence (100 rev min(-1)) level-ground (Int(100)) interval training on power output (PO) during 20-min uphill (TT(up)) and flat (TT(flat)) time-trials. Eighteen male cyclists ([Formula: see text]: 58.6 ± 5.4 mL min(-1) kg(-1)) were randomly assigned to Int(60), Int(100) or a control group (Con). The interval training comprised two training sessions per week over 4 weeks, which consisted of six bouts of 5 min at the PO corresponding to the respiratory compensation point (RCP). For the control group, no interval training was conducted. A two-factor ANOVA revealed significant increases on performance measures obtained from a laboratory-graded exercise test (GXT) (P (max): 2.8 ± 3.0%; p < 0.01; PO and [Formula: see text] at RCP: 3.6 ± 6.3% and 4.7 ± 8.2%, respectively; p < 0.05; and [Formula: see text] at ventilatory threshold: 4.9 ± 5.6%; p < 0.01), with no significant group effects. Significant interactions between group and uphill and flat time-trial, pre- versus post-training on PO were observed (p < 0.05). Int(60) increased PO during both TT(up) (4.4 ± 5.3%) and TT(flat) (1.5 ± 4.5%). The changes were -1.3 ± 3.6, 2.6 ± 6.0% for Int(100) and 4.0 ± 4.6%, -3.5 ± 5.4% for Con during TT(up) and TT(flat), respectively. PO was significantly higher during TT(up) than TT(flat) (4.4 ± 6.0; 6.3 ± 5.6%; pre and post-training, respectively; p < 0.001). These findings suggest that higher forces during the low-cadence intervals are potentially beneficial to improve performance. In contrast to the GXT, the time-trials are ecologically valid to detect specific performance adaptations.
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Westendorf ML, Williams C, Burk AO, Trottier N, Martinson K, Siciliano PD, Swinker AM, Greene EA, Bott R (2012). Environmental Impacts of Equine Operations: a U.S. Department of Agriculture Multistate Project.
Journal of Equine Veterinary Science,
32(6), 324-326.
Abstract:
Environmental Impacts of Equine Operations: a U.S. Department of Agriculture Multistate Project
The U.S. Department of Agriculture supports agricultural research by encouraging the formation of multidisciplinary and multi-institutional teams. Project teams focus on agricultural issues related to profitability and economic and environmental sustainability. Recently, a U.S. Department of Agriculture project to study the impact of equine management and feeding practices on the environment was approved. The project, " NE-1041: Environmental Impacts of Equine Operations," is a Northeast regional project but includes research and extension faculty from across the country. The project team includes representatives from Alabama, Connecticut, Kentucky, Louisiana, Maryland, Michigan, Minnesota, New Jersey, North Carolina, Pennsylvania, South Dakota, and Vermont. The goal of this project is to incorporate the best available data on horse management and feeding practices, manure storage and disposal, pasture and cropping management, soil and environmental quality, erosion control, and farm management practices to minimize negative impacts of equine operations on the environment. The specific objectives of the project are to assess existing data on environmental impacts of equine operations, identify gaps in current knowledge, conduct research when data are lacking or nonexistent, and incorporate existing and newly generated data into a systematic description of nutrient flow in soil, water, and air occurring on horse farms. Estimates will be made of pathogen transports and nitrogen (N)-, phosphorus (P)-, potassium (K)-, and energy (carbon)-loss potentials. In addition to identifying system-wide losses on equine farms, another goal of the project is to assist farmers and agricultural professionals in determining the value of equine management practices and other accepted best management practices. © 2012.
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Williams CA, Bailey SD, Mauger AR (2012). External exercise information provides no immediate additional performance benefit to untrained individuals in time trial cycling.
Br J Sports Med,
46(1), 49-53.
Abstract:
External exercise information provides no immediate additional performance benefit to untrained individuals in time trial cycling.
OBJECTIVE: to determine the importance of the provision of external exercise information to the setting of the pacing strategy, in subjects unfamiliar with a cycling task. DESIGN: Twenty-two healthy, untrained cyclists (VO(2max), 50 ± 9 mL-(1)·kg-(1)·min-(1)) were randomly assigned to a control (CON) group or an experimental (EXP) group and two successive 4 km time trials (TT) were performed, separated by a 17 min recovery. The CON group received distance knowledge and distance feedback; the EXP group received neither, but knew that each TT was to be of the same distance. RESULTS: No significant difference in completion time (p>0.05) was observed between the groups for either time to complete TT one (TT1) (CON=443 ± 33 s versus EXP=471 ± 63 s) or time to complete TT two (time trial 2) (CON=461 ± 37 s versus EXP=501 ± 94 s). No significant difference in the final RPE was observed between groups. However, a significant interaction for RPE (rating of perceived exertion)×TT in the CON was observed (F7,70=5.32, p
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Williams CA, Blackwell J (2012). Hydration status, fluid intake, and electrolyte losses in youth soccer players.
Int J Sports Physiol Perform,
7(4), 367-374.
Abstract:
Hydration status, fluid intake, and electrolyte losses in youth soccer players.
The purpose of the study was to determine the hydration status, fluid intake, and electrolyte losses of 21 male professional youth soccer players (age 17.1 ± 0.7 y) training in a cool environment. Pretraining and posttraining measurements of body mass, urine (freezing-point osmolality method), and sweat concentration (flame-emission spectroscopy) were collected. Fourteen players were found to be hypohydrated before training. The amount of fluid lost due to exercise equated to a 1.7% loss in body mass, which equated to a gross dehydration loss of 0.5%. Overall, the soccer players replaced 46% ± 88% of sweat loss during training, and only 4 remained hypohydrated after training. No significant correlations between sweat loss and sweat concentrations of Na+ (r = -.11, P =. 67) or K+ (r =. 14, P =. 58) were found, but there was a significant correlation with Mg2+ (r = -.58, P <. 009). This study found large variability in pretraining hydration status that the players were able to rehydrate during the training sessions. However, given the numbers starting training in a hypohydrated state, adequate hydration status before training should be considered by youth players, coaches, and sports-science support staff.
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Andersen TB, Bendiksen M, Pedersen JM, Ărntoft C, Brito J, Jackman SR, Williams CA, Krustrup P (2012). Kicking velocity and physical, technical, tactical match performance for U18 female football players--effect of a new ball.
Hum Mov Sci,
31(6), 1624-1638.
Abstract:
Kicking velocity and physical, technical, tactical match performance for U18 female football players--effect of a new ball.
We investigated kicking velocity and physical, technical, and tactical match performance for under-18 (U18) female football players and evaluated the effect of using a newly developed lighter smaller ball. Ten regional league teams participated. Maximal ball velocity was 4±1% higher when kicking the new ball (NB) compared with the standard ball (SB) in a laboratory testing situation (23.2±0.4 vs. 22.4±0.3 ms(-1); p.05), but lower-limb muscular RPE was lower with NB (4.2±0.4 vs. 5.2±0.3; p.05). High-intensity running decreased (p.05). In conclusion, physiological demands were high in youth female football games, and decrements in running performance occurred towards the end of games. The players kicked faster and reported lower muscular exertion during games played with a lighter smaller ball, but locomotor activities, heart rate and overall technical-tactical game performance remained unaffected.
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Breese BC, Barker AR, Armstrong N, Jones AM, Williams CA (2012). The effect of baseline metabolic rate on pulmonary Oâ 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 Oâ uptake kinetics during very heavy intensity exercise in boys and men.
This study tested the hypothesis that pulmonary VOâ 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
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Lloyd RS, Oliver JL, Hughes MG, Williams CA (2012). The effects of 4-weeks of plyometric training on reactive strength index and leg stiffness in male youths.
J Strength Cond Res,
26(10), 2812-2819.
Abstract:
The effects of 4-weeks of plyometric training on reactive strength index and leg stiffness in male youths.
Although previous pediatric research has reported performance improvements in muscular power, agility, speed, and rate-of-force development after exposure to plyometric training, the effects on reactive strength index (RSI) and leg stiffness remain unclear. One hundred and twenty-nine boys from 3 different age groups (9, 12, and 15 years) participated and were divided into either an experimental (EXP) or control (CON) group within their respective age groups. The EXP groups followed a twice-weekly, 4-week plyometric training program, whereas the CON groups participated in their normal physical education lessons. Preintervention and postintervention measures were collected for RSI (during maximal hopping) and leg stiffness (during submaximal hopping). Both 12- and 15-year-old EXP groups made significant improvements in both absolute and relative leg stiffness (p < 0.05). The 9-year-old EXP group and CON groups for all ages did not make significant changes in leg stiffness. The 12-year-old EXP cohort also made significant improvements in RSI (p < 0.05). Both 15- and 9-year-old EXP cohorts, and CON groups for all ages, failed to show any significant improvements in RSI. The study concludes that improvements in RSI and leg stiffness after a 4-week plyometric training program are age dependent during childhood.
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Eastman S, Redden RF, Williams CA (2012). Venograms for Use in Laminitis Treatment.
Journal of Equine Veterinary Science,
32(11), 757-759.
Abstract:
Venograms for Use in Laminitis Treatment
Venography is a very valuable tool that can be used in the diagnosis and treatment of laminitis. It can be used to assess vascular damage in the hoof before changes in radiographic detail occur. When used at onset, the venogram proves to be most valuable. They can not only give baseline measurements but can also show the level of damage that has already occurred. Initial venograms allow farriers and veterinarians to evaluate what degree of corrective treatment is necessary for the best outcome. In addition, a series of venograms can show the process of pathology as well as recovery. From here, treatment can be altered to accommodate the case. © 2012.
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Williams CA, Saynor ZL, Barker AR, Oades PJ (2012). WS16.2 the reliability of maximal cardiopulmonary exercise testing for young cystic fibrosis patients. Journal of Cystic Fibrosis, 11
Armstrong N (2012). Young people are fit and active - Fact or fiction?.
JOURNAL OF SPORT AND HEALTH SCIENCE,
1(3), 131-140.
Author URL.
Williams CA, Armstrong N (2011). Children and exercise XXVII: the proceedings of the XXVII<sup>th</sup> international symposium of the European group of Pediatric work physiology, September, 2011.
International Symposium of the European Group of Pediatric Work Physiology, September, 2011, 1-333.
Abstract:
Children and exercise XXVII: the proceedings of the XXVIIth international symposium of the European group of Pediatric work physiology, September, 2011
Children and Exercise XXVII presents the latest scientific research into paediatric sport and exercise science and medicine, including contributions from a wide range of leading international experts and early career researchers. The book begins with chapters devoted to the five invited keynote lectures, followed by forty-two of the peer-reviewed presentations which are arranged into five thematic sections addressing:
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Bouchant A, Abdelmoula A, Martin V, Lavet C, Williams CA, Ratel S (2011). Comparative analysis of quadriceps endurance during sustained submaximal isometric contractions in children and adults. , 91-95.
Barker AR, Bond B, Toman C, Williams CA, Armstrong N (2011). Critical power in adolescents: physiological bases and assessment using all-out exercise. European Journal of Applied Physiology, 1-12.
Williams C (2011). Environmental factors affecting elite young athletes.
Med Sport Sci,
56, 150-170.
Abstract:
Environmental factors affecting elite young athletes.
To date, much of the research concerning the performance of elite young athletes has focused on physical and physiological factors and how these relate to age and maturation. Little attention has been paid to other factors which might limit performance such as nutrition or environmental stressors. The paucity of research on the environmental effects on performance in young athletes is unsurprising given the need for experimental studies, the ethics of which would generally be untenable. As an outcome, there is a reliance on observational and case study data, e.g. observing the stressors which occur during jet lag and effects on sleep patterns, altitude and pollution. The effects of environmental factors have been predominantly researched from a health context in youngsters rather than a performance context. However, the evidence of those few empirical studies combined with coach and/or sports science support teams' experience have provided professionals with some guidelines. These applied guidelines include sleep patterns, jet lag, pollution and altitude research, to aid those preparing young athletes for training and competition in environments that present potential challenges to performance. The limitations of data extrapolated from adults are acknowledged and in all cases it is emphasised that recommendations and implementing practice should be based on data collected from young people.
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Barker AR, Williams CA, Jones AM, Armstrong N (2011). Establishing maximal oxygen uptake in young people during a ramp cycle test to exhaustion.
BRITISH JOURNAL OF SPORTS MEDICINE,
45(6), 498-503.
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Stevens D, Oades PJ, Armstrong N, Williams CA (2011). Exercise metabolism during moderate-intensity exercise in children with cystic fibrosis following heavy-intensity exercise.
Appl Physiol Nutr Metab,
36(6), 920-927.
Abstract:
Exercise metabolism during moderate-intensity exercise in children with cystic fibrosis following heavy-intensity exercise.
Muscle metabolism is increased following exercise in healthy individuals, affecting exercise metabolism during subsequent physical work. We hypothesized that following heavy-intensity exercise (HIE), disease factors in children with cystic fibrosis (CF) would further exacerbate exercise metabolism and perceived exertion during subsequent exercise. Nineteen children with CF (age, 13.4 ± 3.1 years; 10 female) and 19 healthy controls (age, 13.8 ± 3.5 years; 10 female) performed 10 bouts of HIE interspersed with 1 min of recovery between each bout. Three minutes later participants completed a 10-min moderate-intensity exercise (MIE) test (test 1). The MIE test was subsequently repeated 1 h (test 2) and 24 h (test 3) later. Each MIE test was identical and participants exercised at individualized work rates, calibrated by an initial graded maximal cardiopulmonary exercise test, while metabolic and perceived exertion measurements were taken. Following HIE, mixed-model ANOVAs showed a significant difference in oxygen uptake (VOâ) and rating of perceived exertion (RPE) between the 2 groups across the MIE tests (p < 0.01). In controls, VOâ (L·min⻹) and RPE decreased significantly from test 1 to test 2 (p < 0.01) and test 2 to test 3 (p < 0.05). However, in children with CF, VOâ (L·min⻹) increased significantly from test 1 to test 2 (p < 0.01), while RPE did not differ, both VOâ and RPE decreased significantly from test 2 to test 3 (p < 0.01). In conclusion, following HIE the metabolic and perceptual responses to MIE in both groups decreased 24 h later during test 3. These data show that children with mild-to-moderate CF have the capability to perform HIE and 24 h allows sufficient time for recovery.
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Nimmerichter A, Eston RG, Bachl N, Williams C (2011). Longitudinal monitoring of power output and heart rate profiles in elite cyclists.
J Sports Sci,
29(8), 831-840.
Abstract:
Longitudinal monitoring of power output and heart rate profiles in elite cyclists.
Power output and heart rate were monitored for 11 months in one female (V(.)O(2max): 71.5 mL · kg⻹ · min⻹) and ten male (V(.)O(2max): 66.5 ± 7.1 mL · kg⻹ · min⻹) cyclists using SRM power-meters to quantify power output and heart rate distributions in an attempt to assess exercise intensity and to relate training variables to performance. In total, 1802 data sets were divided into workout categories according to training goals, and power output and heart rate intensity zones were calculated. The ratio of mean power output to respiratory compensation point power output was calculated as an intensity factor for each training session and for each interval during the training sessions. Variability of power output was calculated as a coefficient of variation. There was no difference in the distribution of power output and heart rate for the total season (P = 0.15). Significant differences were observed during high-intensity workouts (P < 0.001). Performance improvements across the season were related to low-cadence strength workouts (P < 0.05). The intensity factor for intervals was related to performance (P < 0.01). The variability in power output was inversely associated with performance (P < 0.01). Better performance by cyclists was characterized by lower variability in power output and higher exercise intensities during intervals.
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Matos NF, Winsley RJ, Williams CA (2011). Prevalence of nonfunctional overreaching/overtraining in young English athletes.
Med Sci Sports Exerc,
43(7), 1287-1294.
Abstract:
Prevalence of nonfunctional overreaching/overtraining in young English athletes.
PURPOSE: Nonfunctional overreaching and overtraining (NFOR/OT) in adults can lead to significant decrements in performance, combined with physical and psychological health problems. Little is known about this condition in young athletes by comparison; thus, the aim of the study was to assess the incidence and symptomatology of NFOR/OT in young English athletes. METHODS: Three hundred seventy-six athletes (131 girls and 245 boys, age=15.1±2.0 yr) completed a 92-item survey about NFOR/OT. The sample included athletes competing at club to international standards across 19 different sports. Athletes were classified as NFOR/OT if they reported persistent daily fatigue and a significant decrement in performance that lasted for long periods of time (i.e. weeks to months). Data were analyzed using the Mann-Whitney U and the Kolmogorov-Smirnov nonparametric tests. Significant predictors of NFOR/OT were identified using logistic regression analysis. RESULTS: One hundred ten athletes (29%) reported having been NFOR/OT at least once. The incidence was significantly higher in individual sports (P
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Williams CA, Oliver JL, Faulkner J (2011). Seasonal monitoring of sprint and jump performance in a soccer youth academy.
Int J Sports Physiol Perform,
6(2), 264-275.
Abstract:
Seasonal monitoring of sprint and jump performance in a soccer youth academy.
PURPOSE: the aim of the study was to longitudinally assess speed and jump performance characteristics of youth football players over a 3 y period. METHODS: Two hundred players across five age squads (U12-U16) from an English Football League academy participated. Sprint performance (10 and 30 m) and countermovement jump height were assessed at 6 mo intervals. Pairwise analyses determined the level of change in performance between consecutive intervals. RESULTS: Sprint performance changes tended to be greatest during the early teenage years, with observed changes exceeding the smallest worthwhile effect (1.0% for 10 and 30 m sprints). Changes in jump performance were above the smallest worthwhile effect of 1.8% for all but one interval. Large individual variability in the magnitude of change in sprint and jump performance, perhaps due to the confounding effect of growth and maturation, revealed few significant differences across the 6 mo intervals. Cumulative changes in performance demonstrated strong linear relationships, with a yearly rate of change of 6.9% for jump height, and 3.1 and 2.7% for 10 m and 30 m sprint time respectively. The magnitude of change in performance tended not to differ from one interval to another. CONCLUSIONS: the results of this study may primarily be used to monitor and predict the rate of progression of youth football players. In addition, these results may be used as a benchmark to evaluate the effectiveness of a current training program.
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Lloyd RS, Oliver JL, Hughes MG, Williams CA (2011). Specificity of test selection for the appropriate assessment of different measures of stretch-shortening cycle function in children.
JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS,
51(4), 595-602.
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Ford P, de Ste Croix M, Lloyd R, Meyers R, Moosavi M, Oliver J, Till K, Williams C (2011). The Long-Term Athlete Development model: Physiological evidence and application.
Journal of Sports Sciences,
29(4), 389-402.
Abstract:
The Long-Term Athlete Development model: Physiological evidence and application
Within the UK, the "Long Term Athlete Development" (LTAD) model has been proposed by a variety of national governing bodies to offer a first step to considering the approach to talent development. The model, which is primarily a physiological perspective, presents an advancement of understanding of developing athletic potential alongside biological growth. It focuses on training to optimize performance longitudinally, and considers sensitive developmental periods known as "windows of opportunity". However, it appears that there are a number of problems with this theoretical model that are not necessarily transparent to coaches. Principally, the model is only one-dimensional, there is a lack of empirical evidence upon which the model is based, and interpretations of the model are restricted because the data on which it is based rely on questionable assumptions and erroneous methodologies. Fundamentally, this is a generic model rather than an individualized plan for athletes. It is crucial that the LTAD model is seen as a "work in progress" and the challenge, particularly for paediatric exercise scientists, is to question, test, and revise the model. It is unlikely that this can be accomplished using classical experimental research methodology but this should not deter practitioners from acquiring valid and reliable evidence. © 2011 Taylor & Francis.
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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
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Breese BC, Armstrong N, Barker AR, Williams CA (2011). The effect of pedal rate on pulmonary O2 uptake kinetics during very heavy intensity exercise in trained and untrained teenage boys.
Respir Physiol Neurobiol,
177(2), 149-154.
Abstract:
The effect of pedal rate on pulmonary O2 uptake kinetics during very heavy intensity exercise in trained and untrained teenage boys.
This study tested the hypothesis that the VO2 kinetic response would be slowed in untrained (UT) but not trained (T) teenage participants whilst cycling at 115 rev min(-1) compared to 50 rev min(-1). Eight UT and seven T boys completed two square-wave transitions to very heavy-intensity exercise pedalling at 50 rev min(-1) and 115 rev min(-1). In UT at the higher pedal rate, the phase II VO2 was significantly (P < 0.01) slower (50 rev min(-1): 32 ± 5 vs. 115 rev min(-1): 42 ± 11 s) and the relative VO2 slow component was significantly (P < 0.01) elevated (50 rev min(-1): 10 ± 3 vs. 115 rev min(-1): 16 ± 5%). The phase II VO2 (50 rev min(-1): 26 ± 4 vs. 115 rev min(-1): 22 ± 6s) and relative VO2 slow component (50 rev min(-1): 14 ± 5 vs. 115 rev min(-1): 17 ± 3%) were unaltered by pedal rate in T (P > 0.05). These data are consistent with the notion that VO2 kinetics are influenced by muscle fibre recruitment in youth but this effect is attenuated in endurance trained teenage boys.
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Williams CA, Aucouturier J, Doré E, Duché P, Ratel S (2011). The health benefits of aerobic activity and physical fitness in young people.
, 143-167.
Abstract:
The health benefits of aerobic activity and physical fitness in young people
Results from studies involving adult participants have definitively established that physical activity and cardiorespiratory fitness are inversely correlated to morbidity and mortality. The evidence of the health benefits for physically active and fit adults is well known. There is a wealth of data which has shown that physically active and fit adults can help attenuate the effects of hypertension, insulin resistance, hyperlipidemia, obesity and cancer. However, the relationship between activity, fitness and the health benefits during childhood are less well established. Although it is intuitive to propose that an active child will become an active adult, the research evidence is weak. Similarly, the extent to which children's fitness and activity must decrease to seriously compromise their current or future health is also unknown. There is however growing concern for the future health status of children due to the increased levels of overweight and obese children and increased reporting of cardiovascular risk factors. Prospective data is needed to elucidate the complexity of these relationships. This complexity is partially due to problems related to 1) methodology i.e. how do we measure activity and health outcomes precisely; 2) biology i.e. children are growing and maturing at different rates and 3) sociology i.e. the effects of the environment. These problems therefore pose real challenges for policy makers as to whether they should concentrate resources on those child individuals who are deemed =at risk' i.e. low fitness and low physical activity patterns or to focus across the whole child population. This review will explore the relationships between physical fitness, activity and health in young people as well as describing the evidence for health benefits in this age group. The review will also discuss the implications for strategies of health related physical activity promotion at local and national levels. © 2011 by Nova Science Publishers, Inc. All rights reserved.
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Lloyd RS, Oliver JL, Hughes MG, Williams CA (2011). The influence of chronological age on periods of accelerated adaptation of stretch-shortening cycle performance in pre and postpubescent boys.
J Strength Cond Res,
25(7), 1889-1897.
Abstract:
The influence of chronological age on periods of accelerated adaptation of stretch-shortening cycle performance in pre and postpubescent boys.
Although it is suggested that periods of naturally occurring accelerated adaptation may exist for various physical parameters, it would appear that no such evidence exists for stretch-shortening cycle (SSC) development. Two hundred and fifty male youths aged 7-17 years were tested for squat (SJ) and countermovement jump (CMJ) height, reactive strength index (RSI), and leg stiffness, with analyses of variance used to establish any significant between-group differences. Additionally, to ascertain the existence of periods of accelerated adaptation, inferences were made about the magnitudes of change between consecutive chronological age groups in relation to the smallest worthwhile change. The largest mean differences (±90% confidence limits) occurred between age groups 10 and 11 (G10-G11) for squat jump (SJ) height (21.61 ± 12.08-31.94%), CMJ height (20.80 ± 11.1-44.1%), and RSI (26.51 ± 11.07-44.10%); and between G12 and G13 for SJ (15.31 ± 7.47-23.73%) and CMJ (16.09 ± 7.50-25.38%) height. Negative mean differences occurred between G11 and G12 for SJ height (-1.32 ± -9.30 to 7.37%), CMJ jump height (-7.68 ± -15.15 to 0.45%) and RSI (-11.48 ± -22.21 to 0.74%); and between G10 and G11 for leg stiffness (-8.87 ± -18.85 to 2.34%). It would appear almost certain that windows of accelerated adaptation may exist for SJ and CMJ height and RSI in male youths; however, leg stiffness results would suggest that fast-SSC function may follow a different developmental trend.
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Stevens D, Oades PJ, Armstrong N, Williams CA (2010). A survey of exercise testing and training in UK cystic fibrosis clinics.
J Cyst Fibros,
9(5), 302-306.
Abstract:
A survey of exercise testing and training in UK cystic fibrosis clinics.
BACKGROUND: Exercise testing is a valuable prognostic tool and exercise training has many health benefits in cystic fibrosis (CF). The objective of this study was to survey the provision of exercise testing and training in UK CF clinics. METHODS: a three-page questionnaire was used to determine the extent of, scope and importance assigned to exercise testing and training. RESULTS: Data from returned questionnaires showed that 38.9% of paediatric and 27.8% of adult patients had performed an exercise test in the preceding 12 months, most as part of an annual review process. Pulmonary rehabilitation programmes were accessible in only 31.3% of clinics, and only 26.0% provide exercise training programmes. When assigning importance for exercise testing on a scale from 1 'not important' to 5 'very important', the mean and median respondent scores were 3.5 and 4.0, respectively, and for the importance of training were 4.0 and 4.0, respectively. CONCLUSIONS: Despite the level of importance given to exercise testing and training by healthcare providers, exercise is underused as either an assessment tool or therapeutic intervention in the healthcare of patients with CF in the UK.
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Willcocks RJ, Williams CA, Barker AR, Fulford J, Armstrong N (2010). Age- and sex-related differences in muscle phosphocreatine and oxygenation kinetics during high-intensity exercise in adolescents and adults.
NMR IN BIOMEDICINE,
23(6), 569-577.
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Williams CA (2010). Antioxidant supplementation to the exercising horse.
Revista Brasileira de Zootecnia,
39(SUPPL. 1), 145-150.
Abstract:
Antioxidant supplementation to the exercising horse
Evidence of oxidative stress in horses has been described in reports dealing with intense and endurance exercise. Oxidative stress occurs when antioxidant systems are insufficient causing oxidation to potentially damage DNA, proteins, and lipids, and contribute to degenerative changes. Vitamin E is the most commonly supplemented antioxidant in horses and has been shown that horses in exercise conditioning may require higher intakes of vitamin E than recommended. Also in various species vitamin C potentiates the effects of vitamin E; however, under maintenance conditions horses have the ability to synthesize sufficient ascorbate, the demand increases as stress on the body is increased. Competitive endurance horses were estimated to consume 1.2 to 5-times higher levels of vitamin E than recommended intakes. In these horses a negative correlation was found between the vitamin E intake and creatine kinase, and aspartate aminotransferase. Similarly, three-day event horses have vitamin E average intakes about 50% over recommended levels, and it was also found that intake of vitamin E negatively correlated with inflammatory markers. However, large doses of vitamin E at about 10-times the recommended levels could potentially interfere with beta-carotene absorption. While some studies have shown benefits of lipoic acid supplementation in endurance trained horses similar to that of vitamin E, other studies failed to show any benefit of supplemental superoxide dismutase in intensely exercising horses. The implications from this broad scope of work show potential benefits for supplementing various antioxidants however, before assuming efficacy from other species horse specific studies should be performed. © 2010 Sociedade Brasileira de Zootecnia.
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Westendorf ML, Joshua T, Komar SJ, Williams C, Govindasamy R (2010). CASE STUDY: Manure Management Practices on New Jersey Equine Farms.
Professional Animal Scientist,
26(1), 123-129.
Abstract:
CASE STUDY: Manure Management Practices on New Jersey Equine Farms
The number of equine farms is increasing in Northeast and Mid-Atlantic states. These farms may influence environmental and water quality because of manure collection, storage, spreading, and disposal practices. A manure management survey was mailed to 2,000 New Jersey equine farms during the winter of 2006 to 2007. of the 2,000 surveys sent, 472 were returned; 18.5% were from training or performance farms, and the remainder (81.5%) were from breeding, boarding, or pleasure farms. Fifty-four percent of all farms spread manure on their farms. of those who spread manure, only 27% had more than 8.09 ha (20 acres) available for spreading. Seventy-four percent had a designated area for manure storage. Eighty-three percent said their manure storage was greater than 61 m (200 ft) from water or wetlands, and 86% said storage was greater than 61 m (200 ft) from neighbors. Data were modeled to determine the relationship between manure storage or manure spreading and other management practices. The storage model showed that farms with 6 to 10 horses were more likely to have storage facilities than farms not included in the model. This model had a predictive accuracy of 83.3% and an R2 of 0.35 (P > 0.01). The manure spreading model showed that those who spread manure were also likely to credit manure for its fertilizer value. The spreading model had an overall predictive accuracy of 95.5% and an R2 of 0.795 (P > 0.01). These results indicate that although most equine farms did not pose a direct risk to water quality or to a neighbor, most do not currently use best management practices in managing, spreading, or storing manure.
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Greene EA, Griffin AS, Whittle J, Williams CA, Howard AB, Anderson KP (2010). Development and usage of eXtension's HorseQuest: an online resource.
Journal of Animal Science,
88(8), 2829-2837.
Abstract:
Development and usage of eXtension's HorseQuest: an online resource
eXtension (pronounced e-extension) is an online resource transforming how faculty can collaborate and deliver equine education. As the first Community of Practice launched from extension, HorseQuest (HQ) offers free, interactive, peer-reviewed, online resources on a variety of equine-related topics at http://www.extension.org. This group has adapted traditional educational content to the online environment to maximize search engine optimization, to be more discoverable and relevant in the online world. This means that HQ resources are consistently being found on the first page of search results. Also, by researching key words searched by Internet users, HQ has guided new content direction and determined potential webcast topics based on relevance and frequency of those searches. In addition to establishing good search engine optimization, HQ has been utilizing the viral networking aspect of YouTube by uploading clips of existing equine educational videos to YouTube. HorseQuest content appears in mainstream media, is passed on by the user, and helps HQ effectively reach their community of interest (horse enthusiasts). HorseQuest partners with My Horse University to produce webcasts that combine concise knowledge exchange via a scripted presentation with viewer chat and incoming questions. HorseQuest has produced and published content including 12 learning modules, 8 webchats, 21 webcasts, and 572 videos segments. After the official public launch, there was a steady increase in average number of visits/mo and average page views/mo over the 26-mo period. These regressions show a statistically significant increase in visits (P < 0.001) of approximately 450 visits per month and a significant increase in page views (P = 0.004) of about 373 page views per month. HorseQuest is a resource for several state 4-H advancement and competition programs and will continue to be incorporated into traditional extension programs, while reaching and affecting global audiences. © 2010 American Society of Animal Science.
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Westendorf ML, Joshua T, Komar SJ, Williams C, Govindasamy R (2010). Effectiveness of Cooperative Extension Manure Management Programs.
Journal of Equine Veterinary Science,
30(6), 322-325.
Abstract:
Effectiveness of Cooperative Extension Manure Management Programs
Equine farms are increasing in number in many areas of the United States. Unlike traditional farming operations, equine farm managers may be less likely to use and are less connected to extension services. A manure management survey was mailed to 2000 New Jersey equine farms during the winter of 2006 to 2007; 472 surveys were returned (24% return rate). Respondents were asked from where they get manure management information; 27% received information from Rutgers Cooperative Extension, whereas 21% get information from a feed dealer, 6% from another retailer, 19% from the internet, 39% from magazines, 47% from other horse owners, and 25% from other sources. Veterinarians were not a variable in this survey; although they are a source of equine information, it is unclear how reliable a source they might be about manure management. They can play a role in manure management programs, particularly referral to other sources of information. Data were modeled to compare extension against all other sources and develop a prediction of where respondents receive information. This model had a predictive accuracy of 70.03% and R2 of 0.08 (P >. 10). This model showed that those receiving information from extension were likely to have 21 to 40 acres of pasture, were likely to spread manure on 6 to 10 acres, and likely to soil test regularly. Results indicate that cooperative extension was not the first or second information source for horse producers, although larger farms and those that soil tested on a regular basis were more likely to use extension services (P <. 05).
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Nimmerichter A, Williams C, Bachl N, Eston R (2010). Evaluation of a field test to assess performance in elite cyclists.
Int J Sports Med,
31(3), 160-166.
Abstract:
Evaluation of a field test to assess performance in elite cyclists.
The study aimed to assess the reproducibility of power output during a 4 min (TT4) and a 20 min (TT20) time-trial and the relationship with performance markers obtained during a laboratory graded exercise test (GXT). Ventilatory and lactate thresholds during a GXT were measured in competitive male cyclists (n=15; (.)VO (2max) 67+/-5 ml x min (-1) x kg (-1); P (max) 440+/-38W). Two 4 min and 20 min time-trials were performed on flat roads. Power output was measured using a mobile power-meter (SRM). Strong intraclass-correlations for TT4 ( R=0.98; 95% CL: 0.92-0.99) and TT20 ( R=0.98; 95% CL: 0.95-0.99) were observed. TT4 showed a bias+/-random error of - 0.8+/-23W or - 0.2+/-5.5%. During TT20 the bias+/-random error was - 1.8+/-14W or 0.6+/-4.4%. Both time-trials were strongly correlated with performance measures from the GXT (p
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Abu-Hasan M, Armstrong N, Andersen LB, Weinberger M, Nixon PA (2010). Exercise in Children during Health and Sickness. International Journal of Pediatrics, 2010, 1-2.
Williams CA, Benden C, Stevens D, Radtke T (2010). Exercise training in children and adolescents with cystic fibrosis: theory into practice.
Int J Pediatr,
2010Abstract:
Exercise training in children and adolescents with cystic fibrosis: theory into practice.
Physical activity and exercise training play an important role in the clinical management of patients with cystic fibrosis (CF). Exercise training is more common and recognized as an essential part of rehabilitation programmes and overall CF care. Regular exercise training is associated with improved aerobic and anaerobic capacity, higher pulmonary function, and enhanced airway mucus clearance. Furthermore, patients with higher aerobic fitness have an improved survival. Aerobic and anaerobic training may have different effects, while the combination of both have been reported to be beneficial in CF. However, exercise training remains underutilised and not always incorporated into routine CF management. We provide an update on aerobic and anaerobic responses to exercise and general training recommendations in children and adolescents with CF. We propose that an active lifestyle and exercise training are an efficacious part of regular CF patient management.
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Montfort-Steiger V, Williams CA, Armstrong N, Fulford J (2010). GASTRIC EMPTYING RATE OF YOUNG CYCLISTS BY MAGNETIC RESONANCE IMAGING: THREE CASE STUDIES.
JOURNAL OF EXERCISE SCIENCE & FITNESS,
8(1), 34-40.
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Mauger AR, Jones AM, Williams CA (2010). Influence of acetaminophen on performance during time trial cycling.
J Appl Physiol (1985),
108(1), 98-104.
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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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Mauger AR, Jones AM, Williams CA (2010). Influence of exercise variation on the retention of a pacing strategy.
Eur J Appl Physiol,
108(5), 1015-1023.
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Influence of exercise variation on the retention of a pacing strategy.
The aim of this study is to establish whether the introduction of an exercise bout of different distance, would affect the retention of the pacing schema stored from a prior exercise bout. Furthermore, to identify whether the 'internal clock' can be calibrated to absolute distance, and whether this is disrupted by exercise requiring a different pacing strategy. Sixteen highly trained male cyclists were randomly allocated into a control (CON) or experimental group (EXP) and completed four time trials (TT) of two different distances (2 x 4 km and 2 x 6 km), separated by 17 min. The participants in the CON group completed both distances in a sequential order whereas the EXP group completed both distances in a variable order. No significant differences in completion time or mean PO were observed (p > 0.05). The CON group showed a significant improvement in their estimation of distance completed in both the 4 km (24.6 +/- 18.2 vs. 8.2 +/- 5.5%) and 6 km (15.2 +/- 7 vs. 8.6 +/- 3%) distances (t (7) = 2.791, t (7) = 3.118, p < 0.05). No significant differences in distance estimation were observed in the EXP group (p > 0.05). In conclusion, participants in the CON group displayed a significant improvement in their judgement of distance completed, despite no improvement in completion time. This suggests that a learned pacing schema is robust and not negatively affected by subsequent pacing variation. The internal clock shows an ability to be calibrated to absolute distance, although this does not improve performance.
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Lamprecht E, Bagnell C, Williams C (2010). Lamprecht et al. Inflammatory responses to three modes of intense exercise in standardbred mares - a pilot study. Comparative Exercise Physiology, 7(3), 151-152.
Breese BC, Williams CA, Barker AR, Weisman JR, Fawkner SG, Armstrong N (2010). Longitudinal Changes in the Oxygen Uptake Kinetic Response to Heavy-Intensity Exercise in 14- to 16-Year-Old Boys (Reprinted from PES, vol 22).
PEDIATRIC EXERCISE SCIENCE,
22(2), 314-325.
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Breese BC, Williams CA, Barker AR, Welsman JR, Fawker SG, Armstrong N (2010). Longitudinal changes in the oxygen uptake kinetic response to heavy-intensity exercise in 14- to 16-year-old boys. Pediatric Exercise Science, 22(1), 69-80.
Williams CA, Burk AO (2010). Nutrient intake during an elite level three-day event competition is correlated to inflammatory markers and antioxidant status.
Equine Veterinary Journal,
42(SUPPL. 38), 116-122.
Abstract:
Nutrient intake during an elite level three-day event competition is correlated to inflammatory markers and antioxidant status
Reasons for performing study: Dietary intake and feeding management practices could affect the degree of physiological stress and subsequent performance of high level 3-day event horses.Objectives: to assess whether a relationship exists between dietary intake levels of selected nutrients and the inflammatory and antioxidant status in horses competing in a high level 3-day event.Materials and methods: Riders competing in a CCI2*/CCI3. 3-day event (n = 35) answered a nutritional management survey conducted by the investigators at the competition. Actual and recommended intakes of vitamin E, potassium (K), calcium (Ca), phosphorus (P) and magnesium (Mg) were calculated using the manufacturer or NRC values. Blood samples, bodyweight and body condition score of horses were taken precompetition, 30 min and 18-24 h after cross-country, but before stadium jumping. Data were analysed using a mixed model ANOVA with repeated measures and Pearson's product moment correlation. Results: Estimated daily intakes of vitamin E, K, Ca, P and Mg for horses were higher than daily recommended levels (P
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Leahy ER, Burk AO, Greene EA, Williams CA (2010). Nutrition-associated problems facing elite level three-day eventing horses.
Equine Veterinary Journal,
42(SUPPL. 38), 370-374.
Abstract:
Nutrition-associated problems facing elite level three-day eventing horses
Reasons for performing study: the main goal of feeding elite 3-day event horses is to deliver nutrients in optimal amounts to allow the horse to maximize its health and performance. However, improper nutritional management and/or physiological stressors related to intense training and competition may increase the risk of nutrition-associated disorders in these horses. An understanding of the nutrition-associated problems contributing to poor performance is critical to the health and welfare of the horse.Objectives: to characterize the nutrition-associated problems affecting top level 3-day event horses during 2008. Methods: Contact information for riders competing in the 2 highest levels of 3-day eventing in 2008 was obtained from the United States Eventing Association. A survey containing 10 questions pertaining to participant demographics and nutrition-associated problems experienced by their horses was mailed and e-mailed to the 81 individuals fitting our criteria of living in USA and Canada. Data was collected in April and May 2009. Results: Twenty-nine of 81 riders completed the survey (35.8%). Respondents rode a total of 45 horses in top level 3-day events in 2008. The top 5 nutrition-associated problems that horses faced at a significantly higher level than the other problems (P
Abstract.
Arent SM, Pellegrino JK, Williams CA, Difabio DA, Greenwood JC (2010). Nutritional supplementation, performance, and oxidative stress in college soccer players.
Journal of Strength and Conditioning Research,
24(4), 1117-1124.
Abstract:
Nutritional supplementation, performance, and oxidative stress in college soccer players
The purpose of this study was to examine changes in performance and metabolic parameters in collegiate soccer players during preseason preparation and to determine the impact of a nutraceutical blend proposed to reduce oxidative stress. Male Division I college soccer players (n = 22) performed a progressive maximal treadmill test at the beginning and end of preseason to assess changes in VO2max, velocity at lactate threshold (VLT), time-to-exhaustion, lipid hydroperoxide (LPO), 8-isoprostane, and creatine kinase (CK) response. After baseline testing, athletes were randomly assigned to receive the nutraceutical blend (EXP; n = 12) or an isocaloric equivalent (CON; n = 10) for 20 days of preseason training. ΔVO2max (2.1 ± 3.3 ml·kg-1·min-1, p = 0.007), ΔVLT (0.8 ± 1.4 km·h-1, p = 0.045), and Dtime-toexhaustion (39.4 ± 77.4 seconds, p = 0.033) were improved across groups, but a significant effect of supplementation on performance was not seen. Changes in resting levels of CK from the beginning to end of preseason were significantly lower (p = 0.044) in EXP (64.8 ± 188.4 U·L-1) than in CON (292.8 ± 304.8 U·L -1). Additionally, EXP demonstrated a significant decrease in the magnitude of the 8-isoprostane response at Trial 2 compared with Trial 1 (effect size [ES] = 20.74), whereas CON had an increased response (ES = 0.20). A similar pattern was seen for LPO (p = 0.067). Preseason training in male college soccer players resulted in significant improvements in VO2max, VLT, and time-to-exhaustion. Supplementing with a proprietary antioxidant and nutraceutical blend may enhance some of these effects as indicated by magnitude of the responses. However, it appears that the most notable effects of supplementation were seen for reduced CK and oxidative stress, at least with short-term supplementation. © 2010 National Strength and Conditioning Association.
Abstract.
Smarsh DN, Liburt N, Streltsova J, McKeever K, Williams CA (2010). Oxidative stress and antioxidant status in intensely exercising horses administered nutraceutical extracts.
Equine Veterinary Journal,
42(SUPPL. 38), 317-322.
Abstract:
Oxidative stress and antioxidant status in intensely exercising horses administered nutraceutical extracts
Reasons for performing study: Many nutraceuticals are used as equine supplements without their efficacy having been scientifically tested. Black tea, cranberries, orange peel and ginger are a few of those nutraceuticals that warrant further study.Objective: to test the effects of single doses of black tea, cranberry, orange peel and ginger extract on markers of oxidative stress and antioxidant status following exercise in horses. Methods: in Study 1, 9 mature, healthy but unfit Standardbred mares were administered 2 l of a control (water), orange peel extract (30 g extract) or decaffeinated black tea extract (28 g extract). In Study 2 the same mares were administered 2 l of a control (water), cranberry extract (30 g extract) or ginger extract (30 g extract). In each study, mares were given the extracts via nasogastric tube 1 h before performing a graded exercise test (GXT), in a randomised crossover design with at least 7 days between GXTs. Blood samples were collected at rest, at fatigue, and 1 and 24 h post exercise and analysed for lipid hydroperoxides (LPO), total glutathione (GSH-T), glutathione peroxidase (GPx), α-tocopherol (TOC), β-carotene (BC) and retinol. Data were statistically analysed using a repeated measures ANOVA. Results: in Study 1 there was no effect of treatment for LPO, GSH-T, GPx, TOC or BC. Retinol was higher for both tea (P = 0.0006) and water (P = 0.004) than for orange peel. In Study 2 there was no treatment effect for LPO, GPx, GSH-T, RET, BC or TOC.Conclusions: the results show that a single dose of various nutraceuticals in exercising horses do not produce an effect on either oxidative stress or antioxidant status and further investigation is needed as to whether long-term supplementation would enhance these effects. © 2010 EVJ Ltd.
Abstract.
Barker AR, Breese BC, Willcocks RJ, Williams CA, Armstrong N (2010). The importance of exercise intensity when studying developmental energy metabolism. Journal of Applied Physiology, 109(5), 1565-1566.
Fiorellino NM, Lamprecht ED, Williams CA (2009). Absorption of Different Oral Formulations of Natural Vitamin E in Horses.
Journal of Equine Veterinary Science,
29(2), 100-104.
Abstract:
Absorption of Different Oral Formulations of Natural Vitamin E in Horses
The objective of this study was to determine the effect of vitamin E source on plasma vitamin E concentration. Five different formulations of natural source vitamin E (4,000 IU/day) were supplemented to Standardbred mares (n = 4 per group) for 14 days. Treatment 1 was given 10 g of 400 IU/g natural acetate (RRR-α-tocopheryl-acetate) powder, treatment 2 was given 6.66 g of 600 IU/g natural acetate powder, treatment 3 was given 6.66 g of 600 IU/g natural alcohol (RRR-α-tocopherol) powder, treatment 4 was given 20 g of 200 IU/g micellized natural alcohol powder, and treatment 5 was given 8 mL of 500 IU/mL micellized natural alcohol liquid. Blood samples were collected before supplementation (day 0), after day 7 and day 14 of supplementation, and analyzed for plasma α-tocopherol. Treatments 1, 2, and 3 increased (P <. 05) from days 0 to 7, but remained similar at day 14. Treatments 4 and 5 also increased (P =. 004, and P <. 0001, respectively) from days 0 to 7 and were higher (P <. 05) than treatment 1, 2, and 3. Plasma levels peaked at day 7 and either plateaued or decreased (treatment 5, P =. 004) at day 14. The micellized alcohol formulations remained elevated (treatment 4) or decreased (treatment 5) after achieving peak blood concentration and, as hypothesized, tended to have plasma concentrations higher than the other vitamin E forms. Care should be taken to ensure that the most active biologically available form of vitamin E is provided in the diet to maximize its efficiency. © 2009 Elsevier Inc. All rights reserved.
Abstract.
De Ste Croix MBA, Deighan MA, Ratel S, Armstrong N (2009). Age and Sex Associated differences in Isokinetic Knee Muscle Endurance Between Young Children and Adults. Applied Physiology, Nutrition and Metabolism, 34, 725-731.
Radtke T, Stevens D, Benden C, Williams CA (2009). Clinical Exercise Testing in Children and Adolescents with Cystic Fibrosis.
PEDIATRIC PHYSICAL THERAPY,
21(3), 275-281.
Author URL.
Dekerle J, Williams C, McGawley K, Carter H (2009). Critical power is not attained at the end of an isokinetic 90-second all-out test in children.
J Sports Sci,
27(4), 379-385.
Abstract:
Critical power is not attained at the end of an isokinetic 90-second all-out test in children.
The purpose of this study was to establish whether critical power, as traditionally determined from the performance of three constant-load tests to exhaustion, is attained at the end of a 90-s all-out test in children. Sixteen healthy children (eight males and eight females; mean age 12.3 years, s(x) = 0.1; body mass 39.6 kg, s(x) = 1.8; peak VO(2) 2.0 litres. min(-1), s(x) = 0.1) completed an incremental test to exhaustion to determine peak oxygen uptake (peak VO(2)), three separate constant-load tests to exhaustion to calculate critical power, and an isokinetic 90-s all-out test. The end power of the 90-s test averaged over the last 10 s (140 W, s(x) = 8) was significantly higher than critical power (105 W, s(x) = 6; t = 6.8; P < 0.01), yet the two parameters were strongly correlated (r = 0.74; P < 0.01). After 60 s, there were no further reductions in power output during the 90-s test (P < 0.0001). In conclusion, at the end of a 90-s all-out test, children are able to produce power outputs well above critical power. This suggests that 90 s is not long enough to completely exhaust the anaerobic work capacity in children.
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Author URL.
Williams CA, Ratel S (2009). Definitions of muscle fatigue. , 3-16.
Stevens D, Oades PJ, Armstrong N, Williams CA (2009). Early oxygen uptake recovery following exercise testing in children with chronic chest diseases.
Pediatr Pulmonol,
44(5), 480-488.
Abstract:
Early oxygen uptake recovery following exercise testing in children with chronic chest diseases.
The value of exercise testing as an objective measure of disease severity in patients with chronic chest diseases (CCD) is becoming increasingly recognized. The aim of this study was to investigate changes in oxygen uptake (VO2) during early recovery following maximal cardiopulmonary exercise testing (CPXT) in relation to functional capacity and markers of disease severity. Twenty-seven children with CCD (age 12.7 +/- 3.1 years; 17 female) [19 children with Cystic fibrosis (CF) (age 13.4 +/- 3.1 years; 10 female) and 8 with other stable non-CF chest diseases (NON-CF) (age 11.1 +/- 2.2 years; 7 female)] and 27 healthy controls (age 13.2 +/- 3.3 years; 17 female) underwent CPXT on a cycle ergometer. On-line respiratory gas analysis measured VO2 before and during CPXT to peak VO2) (VO2(peak)), and during the first 10 min of recovery. Early VO2 recovery was quantified by the time (sec) to reach 50% of the VO2 (peak) value. Early VO2 recovery was correlated against spirometry [forced expiratory volume in 1 sec (FEV(1)) and forced expiratory flow between 25% and 75% of the forced vital capacity (FEF(25-75))] and aerobic fitness (VO2)(peak)) as a measure of functional capacity. Disease severity was graded in the CF patients by the Shwachman score (SS). Compared to controls, children with CCD demonstrated a significantly reduced VO2(peak) (P = 0.011), FEV(1) (P < 0.001), FEF(25-75) (P < 0.001), and a significantly prolonged early (VO2) recovery (P = 0.024). In the CF patients the SS was significantly correlated with early VO2 recovery (r = -0.63, P = 0.004), FEV(1) (r = 0.72, P = 0.001), and FEF(25-75) (r = 0.57, P = 0.011). In the children with CCD, FEV(1), FEF(25-75), and BMI were not significantly correlated with VO2(peak) or early VO2 recovery. Lung function does not necessarily reflect aerobic fitness and the ability to recover from exercise in these patients. A significant relationship was found between VO2(peak) and early VO2 recovery (r = -0.39, P = 0.044) in the children with CCD, showing that a greater aerobic fitness corresponded with a faster recovery.
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Author URL.
Nimmerichter A, Bachl N, Williams C, Eston R (2009). Evaluation of a Field Test to Assess Performance in Elite Cyclists. International Journal of Sports Medicine
Treiber K, Carter R, Gay L, Williams C, Geor R (2009). Inflammatory and redox status of ponies with a history of pasture-associated laminitis.
Veterinary Immunology and Immunopathology,
129(3-4), 216-220.
Abstract:
Inflammatory and redox status of ponies with a history of pasture-associated laminitis
Inflammatory and redox signals could render lamellar tissue susceptible to damage and contribute to higher risk for laminitis in obese or insulin resistant ponies just as these factors contribute to health risks in humans with metabolic syndrome. This study evaluated circulating markers of inflammatory and redox status in ponies that had a history of recurrent bouts of pasture-associated laminitis (PL, n = 42) or had never developed clinical laminitis (NL, n = 34) under the current management conditions. There were no differences (P > 0.05) between PL and NL ponies for markers of antioxidant function (glutathione, glutathione peroxidase, superoxide dismutase) or increased oxidative pressure (malondialdehyde, apoptosis, 3-nitrotyrosine). Inflammatory status, as indicated by fibrinogen concentration, was also not different between pony groups (P = 0.84). However, PL ponies had higher (P < 0.001) plasma concentrations of the pro-inflammatory cytokine TNF-α than NL ponies. This suggests that a predisposition to laminitis is associated with increased circulating inflammatory cytokines. TNF-α could also represent a contributing factor to increased insulin resistance observed in laminitis prone ponies. These results provide new insight into potential mechanisms and risk factors underlying laminitis. © 2008 Elsevier B.V. All rights reserved.
Abstract.
Lamprecht ED, Bagnell CA, Williams CA (2009). Inflammatory responses to three modes of intense exercise in Standardbred mares – a pilot study.
Comparative Exercise Physiology,
5(3-4), 115-125.
Abstract:
Inflammatory responses to three modes of intense exercise in Standardbred mares â a pilot study
The objective of this study was to compare exercise-induced inflammatory responses in horses undergoing three different treadmill exercise tests. Mares completed a graded exercise test (GXT), an interval exercise test (IET) and a repeated sprint exercise test (RSET). Blood and synovial fluid samples were taken 24 h before (PRE) exercise, 20–30 min, 2 and 24 h following exercise (REC). Blood was analysed for total protein, haematocrit and total nitrite concentration. Pro-inflammatory and anti-inflammatory cytokine transcripts were measured in whole blood using quantitative real-time polymerase chain reaction. Synovial fluid was analysed for total nitrite. Mares spent more time at greater than 90% of their maximum heart rate during the RSET than they did for either the GXT or IET. There was an effect of exercise test (P
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.
Williams CA, Willcocks RJ, Barker AR, Fulford J, Armstrong N (2009). Muscle Phosphocreatine Kinetics in Children and Adults During High-intensity Exercise. Medicine & Science in Sports & Exercise, 41(5).
Ratel S, Duché P, Williams CA (2009). Muscle fatigue in children. , 79-102.
Armstrong N, Barker AR (2009). Oxygen uptake kinetics in children and adolescents: a review.
Pediatr Exerc Sci,
21(2), 130-147.
Abstract:
Oxygen uptake kinetics in children and adolescents: a review.
The pulmonary oxygen uptake (pVO2) kinetic response at the onset of exercise provides a noninvasive window into the metabolic activity of the muscle and a valuable means of increasing our understanding of developmental muscle metabolism. However, to date only limited research has been devoted to investigating the pVO2 kinetic response during exercise in children and adolescents. From the rigorous studies that have been conducted, both age- and sex-related differences have been identified. Specifically, children display a faster exponential rise in the phase II pVO2 kinetics, which are purported to reflect the rise in muscle O2 consumption, during moderate, heavy and very heavy intensity exercise compared with adults. Furthermore, for heavy and very heavy exercise, the O2 cost of exercise is higher for the exponential phase and the magnitude of the pVO2 slow component is smaller in young children. Sex-related differences have been identified during heavy, but not moderate exercise, with prepubertal boys displaying a faster exponential phase II pVO2 kinetic response and a smaller pVO2 slow component compared with prepubertal girls. The mechanisms underlying these differences are currently poorly understood, and form the basis for future research in this area. However, it is hypothesized that an age-related modulation of the muscle phosphate feedback controllers to signal an increased rate of oxidative phosphorylation and/or altered muscle fiber type recruitment strategies have the potential to play an important role. Overall, the data support the view that at the onset of exercise children have an enhanced potential for oxidative metabolism in the myocyte compared with adults.
Abstract.
Williams CA, Ratel S (2009). Preface. Human Muscle Fatigue, xvii-xviii.
Williams CA, Ratel S (2009). Preface. Human Muscle Fatigue, 9780203885482, xvii-xviii.
Oliver J, Armstrong N, Williams CAP (2009). Relationship between brief and prolonged repeated sprint ability. Journal of Science and Medicine in Sport, 12, 238-243.
Lloyd RS, Oliver JL, Hughes MG, Williams CA (2009). Reliability and validity of field-based measures of leg stiffness and reactive strength index in youths.
JOURNAL OF SPORTS SCIENCES,
27(14), 1565-1573.
Author URL.
Winsley RJ, Fulford J, Roberts A, Welsman JR, Armstrong N (2009). Sex difference in Peak Oxygen Uptake in Prepubertal Children. Journal of Science and Medicine in Sport, 12, 647-651.
Arent SM, Davitt P, Golem DL, Williams CA, McKeever KH, Jaouhari C (2009). The effects of a post-workout nutraceutical drink on body composition, performance and hormonal and biochemical responses in Division I college football players.
Comparative Exercise Physiology,
6(2), 73-80.
Abstract:
The effects of a post-workout nutraceutical drink on body composition, performance and hormonal and biochemical responses in Division I college football players
Football players walk a fine line between optimal training and overtraining. Manipulating nutrient intake has the potential to maximize the biochemical environment necessary to induce peak performance and proper recovery. The purpose of this study was to examine the impact of supplementing the diet of Division I football players with a proprietary nutraceutical recovery drink on changes in performance, body composition, anabolic status, muscle damage, inflammation and oxidative stress over the course of a 7-week conditioning period immediately prior to preseason camp. At the beginning (trial 1) and end (trial 2) of a 7-week training phase, body composition, vertical jump and 225 lb bench press were assessed in Division I college football players (n = 25). A 30 s Wingate Anaerobic Test plus eight 10 s intervals was used to examine power and biochemical responses. Blood samples were collected pre-, 0 and 60 min post-test for analysis of interleukin-6 (IL), 8-isoprostane (8-iso), cortisol (CORT) and resting testosterone:CORT (T:C) ratios. Athletes were randomly assigned to either an experimental group (EXP) receiving the nutraceutical drink (n = 13) or a control group (CON) receiving an isocaloric equivalent (n = 12). EXP had a significantly greater increase in peak power (P
Abstract.
Brokenshire CS, Armstrong N, Williams CA (2009). The reliability of adolescent thermoregulatory responses during a heat acclimation protocol.
Journal of Sports Science and Medicine,
8(4), 689-695.
Abstract:
The reliability of adolescent thermoregulatory responses during a heat acclimation protocol
This study investigated the between trial variation of thermoregulatory measures during a heat acclimation protocol. Eight 14-16 y old boys completed three bouts of 20-min cycling at 45% peak VO2 in a hot environment (35.1 ± 1.2 °C and 46.4 ± 1.0% relative humidity) on two occasions separated by a minimum of 24 h. Reliability was assessed through analysis of within-subject variation, the change in the mean, and retest correlation for measurements of aural temperature (Tau), mean skin temperature (Tsk), heart rate (HR) and oxygen uptake (VO2). Between trial differences were low for Tau, Tskbout1, Tskbout2and3 and HR with coefficients of variation 0.6%, 1.5%, 0.5% and 4.0%, respectively. The results demonstrate good reliability that will allow future investigators to precisely determine the extent of heat acclimation protocols in relation to the measurement error. © Journal of Sports Science and Medicine.
Abstract.
Williams CA, Gordon ME, Betros CL, McKeever KH (2008). Apoptosis and antioxidant status are influenced by age and exercise training in horses.
Journal of Animal Science,
86(3), 576-583.
Abstract:
Apoptosis and antioxidant status are influenced by age and exercise training in horses
Eight mature (12 ± 2 yr; MAT) and 5 older (22 ±2 yr; OLD) Standardbred mares were used to test the hypothesis that aging and exercise training would alter apoptosis in white blood cells and antioxidant status. The horses were housed indoors overnight (16 h/d) in 3 m × 3 m stalls and were turned out in a drylot during the day. They were fed a diet consisting of total mixed ration, hay cubes fed ad libitum or an equine senior diet plus grass hay. Horses were trained for 20 to 30 min/d, 3 to 5 d/wk for 8 wk at a submaximal work intensity between 60 to 70% of maximal heart rate. A graded exercise test (GXT; stepwise test until exhaustion) was performed before (GXT1) and after (GXT2) the 8 wk of training. During the GXT, blood samples and heart rate were taken at rest, 6 m/s, fatigue, and at 5 and 60 min postfatigue. Fatigue plasma lactate concentration was greater in MAT (19.3 ± 1.5 at 10 m/s) compared with the OLD (10.9 ± 1.2 mmol/L at 9 m/s; P = 0.008) horses. There was no effect of age or training on plasma lipid hydroperoxide (LPO) concentration. However, there was a positive correlation between LPO and plasma lactate concentration (r = 0.27, P = 0.006) during acute exercise. There was a greater concentration of total glutathione after GXT1 than after GXT2 (111.8 ± 5.0 vs. 98.6 ± 3.4 μM, respectively; P = 0.0002) for both age groups. Apoptosis was less (P = 0.002) in white blood cells of the MAT vs. the OLD group. These results demonstrate that older horses are under similar amounts of oxidative stress, measured by LPO, and have similar levels of glutathione in their systems compared with mature horses. The observation that more glutathione was needed during GXT1 for both groups of horses indicates that training helps horses adapt their system for the intense posttraining exercise tests. The greater level of white blood cell apoptosis also indicates that older horses may be immune-compromised during exercise. However, research still needs to be performed regarding dietary supplementation in the aged horse. ©2008 American Society of Animal Science. All rights reserved.
Abstract.
Oliver JL, Armstrong N, Williams CA (2008). Changes in jump performance and muscle activity following soccer specific exercise. Journal of Sports Sciences, 26(2), 141-148.
Williams CA, Dekerle J, McGawley K, Berthoin S, Carter H (2008). Critical power in adolescent boys and girls--an exploratory study.
Appl Physiol Nutr Metab,
33(6), 1105-1111.
Abstract:
Critical power in adolescent boys and girls--an exploratory study.
The purpose of the study was to identify critical power (CP) in boys and girls and to examine the physiological responses to exercise at and 10% above CP (CP+10%) in a sub-group of boys. Nine boys and 9 girls (mean age 12.3 (0.5) y performed 3 constant-load tests to derive CP. Eight of the boys then exercised, in random order, at CP and CP+10% until volitional exhaustion. CP was 123 (28) and 91 (26) W for boys and girls, respectively (p < 0.02), which was equivalent to 75 (6) and 72 (10) % of peak oxygen uptake, respectively (p > 0.47). Boys' time to exhaustion at CP was 18 min 37 s (4 min 13 s), which was significantly longer (p < 0.007) than that at CP+10% (9 min 42 s (2 min 31 s)). End-exercise values for blood lactate concentration (B[La]) and maximal oxygen uptake were higher in the CP+10% trial (5.0 (2.4) mmol.L-1 and 2.15 (0.4) L.min-1, respectively) than in the CP trial, (B[La], 4.7 (2.1) mmol.L-1; maximal oxygen uptake, 2.05 (0.35) L.min-1; p > 0.13). Peak oxygen uptake (expressed as a percentage of the peak value) was not attained at the end of the trials (94 (12) and 98 (14) % for CP and CP+10%, respectively). These results provide information about the boundary between the heavy and severe exercise intensity domains in children, and have demonstrated that CP in a group of boys does not represent a sustainable steady-state intensity of exercise.
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Author URL.
Burk AO, Williams CA (2008). Feeding management practices and supplement use in top-level event horses.
Comparative Exercise Physiology,
5(2), 85-93.
Abstract:
Feeding management practices and supplement use in top-level event horses
The objective of this study was to characterize the nutrition and feeding management practices, including concentrate and supplement use, of three-day event horses prior to and during high-level competition. Subjects were horses competing in one of two divisions at the Jersey Fresh Three-day Event in Allentown, NJ, in 2006 and/or 2007. Body weight and condition score of horses, and feeding management surveys, were completed prior to the start of competition with weight of hay and concentrate taken in 2007. Two sample t-tests were used to compare the data between divisions within each year of the study. For both years, the majority of horses were of the male gender and Thoroughbred breed, aged 11.1 ± 0.3 years. There were no differences between divisions within the year for any of the variables measured. The average numbers of supplements fed on a regular basis to horses competing in the 2006 Concours Complet d'Equitation International (CCI. ), 2006 CCI. 2007 CCI. and 2007 CCI. events were 4.2 ± 0.4, 4.2 ± 0.3, 4.2 ± 0.5 and 4.3 ± 0.7, respectively. In both years, the most administered type of oral supplement was electrolytes, followed by plain salt and oral joint compounds. The majority of horses in both years did not have any change in their forage and concentrate feeding prior to being transported to the show facility. Feeding practices before and after cross-country varied between years and divisions, but most horses had feed withheld for about 2–4 h prior to the event. The majority of feeding management practices followed research-driven recommendations. However, the relatively high average supplement use per horse raises questions about over-supplementation and/or nutrient interactions in these horses. © 2008, Cambridge University Press. All rights reserved.
Abstract.
Willcocks RJ, Barker AR, Fulford J, Welford D, Welsman JR, Armstrong N, Williams CA (2008). Kinetics of Phosphocreatine and Deoxyhemoglobin in Children and Adults During High-Intensity Exercise.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
40(5), S20-S20.
Author URL.
Barker AR, Welsman JR, Fulford J, Welford D, Williams CA, Armstrong N (2008). Muscle phosphocreatine and pulmonary oxygen uptake kinetics in children at the onset and offset of moderate intensity exercise.
Eur J Appl Physiol,
102(6), 727-738.
Abstract:
Muscle phosphocreatine and pulmonary oxygen uptake kinetics in children at the onset and offset of moderate intensity exercise.
To further understand the mechanism(s) explaining the faster pulmonary oxygen uptake (p(VO)(2)) kinetics found in children compared to adults, this study examined whether the phase II p(VO)(2) kinetics in children are mechanistically linked to the dynamics of intramuscular PCr, which is known to play a principal role in controlling mitochondrial oxidative phosphorylation during metabolic transitions. On separate days, 18 children completed repeated bouts of moderate intensity constant work-rate exercise for determination of (1) PCr changes every 6 s during prone quadriceps exercise using (31)P-magnetic resonance spectroscopy, and (2) breath by breath changes in p(VO)(2) during upright cycle ergometry. Only subjects (n = 12) with 95% confidence intervals
Abstract.
Author URL.
Barker AR, Welsman JR, Fulford J, Welford D, Armstrong N (2008). Muscle phosphocreatine kinetics in children and adults at the onset and offset of moderate-intensity exercise.
J Appl Physiol (1985),
105(2), 446-456.
Abstract:
Muscle phosphocreatine kinetics in children and adults at the onset and offset of moderate-intensity exercise.
The splitting of muscle phosphocreatine (PCr) plays an integral role in the regulation of muscle O2 utilization during a "step" change in metabolic rate. This study tested the hypothesis that the kinetics of muscle PCr would be faster in children compared with adults both at the onset and offset of moderate-intensity exercise, in concert with the previous demonstration of faster phase II pulmonary O2 uptake kinetics in children. Eighteen peri-pubertal children (8 boys, 10 girls) and 16 adults (8 men, 8 women) completed repeated constant work-rate exercise transitions corresponding to 80% of the Pi/PCr intracellular threshold. The changes in quadriceps [PCr], [Pi], [ADP], and pH were determined every 6 s using 31P-magnetic resonance spectroscopy. No significant (P>0.05) age- or sex-related differences were found in the PCr kinetic time constant at the onset (boys, 21+/-4 s; girls, 24+/-5 s; men, 26+/-9 s; women, 24+/-7 s) or offset (boys, 26+/-5 s; girls, 29+/-7 s; men, 23+/-9 s; women 29+/-7 s) of exercise. Likewise, the estimated theoretical maximal rate of oxidative phosphorylation (Qmax) was independent of age and sex (boys, 1.39+/-0.20 mM/s; girls, 1.32+/-0.32 mM/s; men, 2.36+/-1.18 mM/s; women, 1.51+/-0.53 mM/s). These results are consistent with the notion that the putative phosphate-linked regulation of muscle O2 utilization is fully mature in peri-pubertal children, which may be attributable to a comparable capacity for mitochondrial oxidative phosphorylation in child and adult muscle.
Abstract.
Author URL.
Williams CA (2008). Oxidative stress or oxidant/antioxidant dis-equilibrium in horses? a hot topic. Veterinary Journal, 177(2), 157-158.
Hess TM, Greiwe-Crandell KM, Waldron JE, Williams CA, Lopes MA, Gay LS, Harris PA, Kronfeld DS (2008). Potassium-free electrolytes and calcium supplementation in an endurance race.
Comparative Exercise Physiology,
5(1), 33-41.
Abstract:
Potassium-free electrolytes and calcium supplementation in an endurance race
Some of the clinical signs seen in horses during endurance races may result from increases in neuromuscular excitability and are related to plasma [K+] and [Ca++]. The present study aimed to test the following hypotheses: (1) Potassium supplementation will affect plasma [K+] and may result in clinical signs related to neuromuscular hyperexcitability during an 80 km endurance ride. (2) Plasma [Ca++] will reflect dietary cation–anion balance (DCAB) and calcium intake. Feeding with a high DCAB and high dietary calcium content (1.5% total calcium of daily ration) diets would lead to higher plasma [Ca++] during an endurance race than on feeding high DCAB diets with a moderate dietary calcium content (1% of total calcium of daily ration). The current study was undertaken during the 80 km endurance research ride in 2002 in Virginia, USA. Forty volunteer rider–horse pairs participated in the race. During the race, electrolyte mixtures with (EM+K) and without (EM − K) potassium were supplied to 18 and 22 horses, respectively. After the race, the horses receiving EM − K during the race were supplied with a recovery formula containing potassium (EM-REC). The horses were fed in addition to their own forage (hay and pasture) either their own commercial concentrate (CC; 1% calcium, n = 11) or one of two research-supplied concentrates during 3 months preceding the research ride, one concentrate rich in sugar and starch (SS; 2% calcium, n = 15) and the other rich in fat and fibre (FF; 2% calcium, n = 14). Peripheral blood samples were taken the day before, within 3 min of the arrival at the vet checks at 27, 48 and 80 km, and after 3 h of recovery. Plasma samples were analysed for pH, haematocrit (Hct), [Na+], [K+], [Cl− ], [Ca++], [Mg++], total protein (TP) and albumin [alb]. Effects of sampling times, treatments and interactions were evaluated by ANOVA in a mixed model with repeated measures and applied to the 25 horses that completed 80 km. Eliminated horses had their blood sampled before entering the elimination vet check and 3 h after elimination, and were compared with finishing horses by t-test. As the ride progressed, significant increases were found in plasma pH, [Na+], [formula omitted], [TP], [alb], Hct and osmolality; and decreases in [K+], [Mg++], PCO2, [Ca++] and [Cl− ]. Horses supplied with potassium-free, sodium-rich electrolyte formulae (EM − K) had 12.5% lower (P = 0.001) mean plasma [K+], 7.8% lower (P = 0.024) TP and 8.4% lower (P = 0.004) albumin at 80 km, and at 3 h after the race they had 6.8% lower (P = 0.045) TP, when compared with EM+K supplemented horses. Horses fed with SS and FF had higher [Ca++] at 27 (P = 0.027), 56 (P = 0.006) and 80 km (P = 0.022) when compared with horses fed with CC. The lower [K+] in the EM − K group, and the higher [Ca++] in the SS- and FF-supplemented horses may help prevent increases in neuromuscular excitability and related clinical signs. The lower TP and albumin indicate less dehydration in the EM − K group and could help prevent related disorders. © 2008, Cambridge University Press. All rights reserved.
Abstract.
Williams CA (2008). Program development for the multisport high school athlete.
Strength and Conditioning Journal,
30(4), 51-55.
Abstract:
Program development for the multisport high school athlete
The majority of high school programs rely on multisport athletes for successful athletic programs. The focus of this article is the development of an athlete and not a sport specific player. This athlete would have the ability to be successful in multiple competitive settings. © National Strength and Conditioning Association.
Abstract.
Barker AR, Welsman JR, Fulford J, Welford D, Armstrong N (2008). Quadriceps Muscle Phosphocreatine and Deoxygenation Kinetics in Children and Adults at the Onset of Moderate Intensity Exercise.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
40(5), S20-S20.
Author URL.
Williams CA, Willcocks RJ, Barker AR, Fulford J, Welford D, Welsman JR, Armstrong N (2008). Recovery of Muscle Oxygenation and Phosphocreatine in Children and Adults Following High-Intensity Quadriceps Exercise.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
40(5), S20-S20.
Author URL.
Nelson MT, Biltz G, Winsley R, Armstrong N, Fawkner S, Bywater K, Dengel DR (2008). Reliability of Heart Rate Variability by Sample Entropy at Rest and During Light Exercise in Children.
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE,
40(5), S282-S282.
Author URL.
Williams CA, Lamprecht ED (2008). Some commonly fed herbs and other functional foods in equine nutrition: a review.
Veterinary Journal,
178(1), 21-31.
Abstract:
Some commonly fed herbs and other functional foods in equine nutrition: a review
Most herbs and functional foods have not been scientifically tested; this is especially true for the horse. This paper reviews some of the literature pertinent to herbal supplementation in horses and other species. Common supplements like Echinacea, garlic, ginger, ginseng, and yucca are not regulated, and few studies have investigated safe, efficacious doses. Ginseng has been found to exert an inhibitory effect on pro-inflammatory cytokines and cyclooxygenase-2 expression. Equine studies have tested the anti-inflammatory effects of a single dose of ginger, post-exercise. Echinacea has been reported to have anti-inflammatory and antioxidant properties. Yucca contains steroid-like saponins, which produce anti-inflammatory, antioxidant, and anti-spasmodic effects. However, some herbs have drug-like actions that interact with dietary components and may contain prohibited substances like salicylates, digitalis, heroin, cocaine and marijuana. Horses fed garlic at >0.2 g/kg per day developed Heinz body anaemia. Drug-herb interactions are common and caution needs to be taken when implementing 'natural product' usage.
Abstract.
Williams CA, Chedzoy S (2008). The Benefits of Being Physically Active. Primary Scienc. Primary Science(March/April), 5-7.
Sharp NCC, Williams CA (2007). 20<sup>th</sup> anniversary of the Children's Health and Exercise Centre, University of Exeter, UK. Journal of Sports Science and Medicine, 6(3).
Montfort-Steiger V, Williams CA (2007). Carbohydrate intake considerations for young athletes. Journal of Sports Science and Medicine, 6(3), 343-352.
Stevens D, Williams CA (2007). Exercise testing and training with the young cystic fibrosis patient. Journal of Sports Science and Medicine, 6(3), 286-291.
Hess TM, Kronfeld DS, Treiber KH, Crandell KE, Waldron JN, Williams CA, Staniar WB, Lopes MA, Harris PA (2007). Fat adaptation affects insulin sensitivity and elimination of horses during an 80 km endurance ride.
Pferdeheilkunde,
23(3), 241-246.
Abstract:
Fat adaptation affects insulin sensitivity and elimination of horses during an 80 km endurance ride
The present study tested the hypothesis that insulin sensitivity would be lower in horses adapted to sugar and starch than those adapted to fat and fiber during an endurance race. Forty horses were divided into 3 dietary groups: one group of experimental feed (SS) was rich in starch (33%), low in fat (8%); another (FF) low in starch (6%) and rich in fat (15%); and a third group of commercial concentrates (CC) was intermediate in starch (16%) and fat (11%). Blood samples were taken the day before the race (PRE), within 3 minutes of arrival at each vet check (after 27, 48, 80 km), and three hours post completion or elimination. Plasma samples were analyzed for glucose, insulin, cortisol, glycerol, triglycerides, CK and AST. A proxy for insulin sensitivity as measured by the minimal model was calculated: RISQI = (1/sqrt [insulin]). Also, a proxy for pancreatic β-cell response to plasma glucose was calculated: MIRG =[800-0.30([insulin] -50)2]/[glucose - 30]. Higher insulin in FF and CC horses, and in eliminated horses, combined with a lower RISQI in eliminated horses indicated that insulin resistance (low RISQI) was attenuated by fat and fiber feeding and decreased the likelihood of elimination. Higher insulin sensitivity in finishers and fat and fiber fed horses may have allowed a more efficient glucose uptake by muscles, allowing energy to be obtained through NEFA and TG. Fat and fiber feeding could avoid insulin resistance improving the efficiency of energy utilization and performance of horses during endurance races it also could reduce excitement and increases in muscle enzymes.
Abstract.
Brickley G, Green S, Jenkins DJ, McEinery M, Wishart C, Doust JH, Williams CA (2007). Muscle metabolism during constant and alternating intensity exercise around critical power. International Journal of Sports Medicine, 28, 303-315.
Brickley G, Green S, Jenkins DG, McEinery M, Wishart C, Doust JD, Williams CA (2007). Muscle metabolism during constant- and alternating-intensity exercise around critical power.
Int J Sports Med,
28(4), 300-305.
Abstract:
Muscle metabolism during constant- and alternating-intensity exercise around critical power.
Few studies have focused on the metabolic responses to alternating high- and low-intensity exercise and, specifically, compared these responses to those seen during constant-load exercise performed at the same average power output. This study compared muscle metabolic responses between two patterns of exercise during which the intensity was either constant and just below critical power (CP) or that oscillated above and below CP. Six trained males (mean +/- SD age 23.6 +/- 2.6 y) completed two 30-minute bouts of cycling (alternating and constant) at an average intensity equal to 90 % of CP. The intensity during alternating exercise varied between 158 % CP and 73 % CP. Biopsy samples from the vastus lateralis muscle were taken before (PRE), at the midpoint and end (POST) of exercise and analysed for glycogen, lactate, PCr and pH. Although these metabolic variables in muscle changed significantly during both patterns of exercise, there were no significant differences (p > 0.05) between constant and alternating exercise for glycogen (PRE: 418.8 +/- 85 vs. 444.3 +/- 70; POST: 220.5 +/- 59 vs. 259.5 +/- 126 mmol x kg (-1) dw), lactate (PRE: 8.5 +/- 7.7 vs. 8.5 +/- 8.3; POST: 49.9 +/- 19.0 vs. 42.6 +/- 26.6 mmol x kg (-1) dw), phosphocreatine (PRE: 77.9 +/- 11.6 vs. 75.7 +/- 16.9; POST: 65.8 +/- 12.1 vs. 61.2 +/- 12.7 mmol x kg (-1) dw) or pH (PRE: 6.99 +/- 0.12 vs. 6.99 +/- 0.08; POST: 6.86 +/- 0.13 vs. 6.85 +/- 0.06), respectively. There were also no significant differences in blood lactate responses to the two patterns of exercise. These data suggest that, when the average power output is similar, large variations in exercise intensity exert no significant effect on muscle metabolism.
Abstract.
Author URL.
Williams CA (2007). Physiological changes of the young athlete and the effects on sports performance. SportEx Medicine, 6-11.
Oliver JL, Armstrong N, Williams CA (2007). Reliability and Validity of a Soccer-Specific Test of Prolonged Repeated-Sprint Ability.
INTERNATIONAL JOURNAL OF SPORTS PHYSIOLOGY AND PERFORMANCE,
2(2), 137-149.
Author URL.
Winsley RJ, Middlebrooke AR, Armstrong N, Williams CA (2006). Aerobic fitness and visceral adipose tissue in children. Acta Paeditrica, 95(11), 1435-1438.
Winsley RJ, Armstrong N, Middlebrooke AR, Ramos-Ibanez N, Williams CA (2006). Aerobic fitness and visceral adipose tissue in children.
Acta Paediatr,
95(11), 1435-1438.
Abstract:
Aerobic fitness and visceral adipose tissue in children.
AIM: to determine the relationship between aerobic fitness (peak VO2) and the volume of visceral adipose tissue (VAT) in children. METHODS: Participants were 30 males (13.7+/-0.5 y) and 22 females (13.5+/-0.5 y). Peak VO2 was determined using a continuous, incremental treadmill protocol to exhaustion. Abdominal VAT volume was measured by magnetic resonance imaging using multiple slices from vertebral levels L1-L5. Subcutaneous body fat measure was calculated as the sum of seven skinfolds (sigma7SKF). RESULTS: Females had significantly (p < or = 0.05) more VAT than males (1035+/-717.3 vs 678.6+/-361.5 cm3); however, male peak VO2 was higher (215+/-34 vs 182+/-20 ml/kg(0.61)/min). VAT was significantly (p < or = 0.05) negatively correlated with peak VO2 in both males (r = - 0.43) and females (r = - 0.45). Subcutaneous body fatness was significantly correlated with VAT in both males (r = 0.74) and females (r = 0.72), and was the single strongest determinant of VAT. CONCLUSION: Aerobic fitness is significantly inversely related to VAT, but subcutaneous body fatness is the single strongest determinant of VAT in children aged 13-14 y.
Abstract.
Author URL.
Ratel S, Williams CA, Oliver J, Armstrong N (2006). Effects of age and recovery duration on performance during multiple treadmill sprints.
Int J Sports Med,
27(1), 1-8.
Abstract:
Effects of age and recovery duration on performance during multiple treadmill sprints.
The aim of this study was to investigate the effects of age and recovery duration on performance during multiple treadmill sprints. Twelve boys (11.7 +/- 0.5 y) and thirteen men (22.1 +/- 2.9 y) performed ten consecutive 10-s sprints on a non-motorised treadmill separated by 15-s (R15) and 180-s (R180) passive recovery intervals. Mean power output (MPO), mean force output (MFO), running velocity, step length, and step rate were calculated for each sprint. Capillary blood samples were drawn from the fingertip at rest and 3 min after the tenth sprint to measure the lactate accumulation (Delta [La]). With R15, all mechanical parameters decreased significantly less in the boys than in the men over the ten sprints (MPO: - 28.9 vs. - 47.0 %, MFO: - 13.1 vs. - 25.6 %, running velocity: - 18.8 vs. - 29.4 %, p < 0.001, respectively). With R180, all mechanical values remained unchanged in the boys. In the men, MPO and MFO significantly decreased over the ten sprints (- 7.8 % and - 4.6 %, p < 0.05, respectively). The running velocity, however, did not decrease because the decrease in step rate (p < 0.001) was compensated by an increase in step length. For either recovery interval, Delta [La] values were higher in the men compared to the boys (R15: 12.7 vs. 7.7 mmol. L (-1), p < 0.001, R180: 10.7 vs. 7.7 mmol. L (-1), p < 0.05). To conclude, the boys maintained more easily their running performance than the men during repeated treadmill sprints with R15. Three-minute recovery periods were sufficient in the boys to repeat short running sprints without substantial fatigue. Despite the decrease in power and force outputs with R180, the young men were able to maintain their running velocity during the test.
Abstract.
Author URL.
Ratel S, Williams CA (2006). Muscle fatigue during high-intensity exercise in children. Sports Medicine, 36, 1031-1065.
Williams CA, Carlucci SA (2006). Oral vitamin E supplementation on oxidative stress, vitamin and antioxidant status in intensely exercised horses.
Equine Veterinary Journal,
38(SUPPL.36), 617-621.
Abstract:
Oral vitamin E supplementation on oxidative stress, vitamin and antioxidant status in intensely exercised horses
Reasons for performing study: Vitamin E is the most commonly supplemented antioxidant in horses; however, previous research is not conclusive as to the recommended level for exercising horses. Objective: to evaluate the effects of 3 levels of vitamin E supplementation on oxidative stress and vitamin/antioxidant status in intensely exercised horses to determine the optimal level of vitamin E supplementation. Methods: Twelve unfit Standardbreds were divided into 3 groups, supplemented orally with 0 (CON), 5000 (MOD), or 10,000 (HI) iu/day of DL-α-tocopheryl acetate. The 3 times 3 Latin square design consisted of three 4 week supplementation periods with 4 week wash out periods between. After each period, horses underwent a treadmill interval exercise test. Blood samples were collected and heart rate (HR) measured before, during and after exercise. Data were analysed using ANOVA with repeated measures in SAS. Results: the CON group had lower HR throughout the test compared to the MOD and HI groups (P
Abstract.
Williams CA, Doust J, Hammond A (2006). Power output and VO2 responses during 30s maximal isokinetic sprints at different cadences in comparison to the Wingate test. Isokinetic and Exercise Science, 14(4), 327-333.
Barker AR, Welsman JR, Welford D, Fulford J, Williams CA, Armstrong N (2006). Reliability of 31P-magnetic resonance spectroscopy during an exhaustive incremental exercise test in children. European Journal of Applied Physiology, 98(6), 556-565.
Barker A, Welsman J, Welford D, Fulford J, Williams C, Armstrong N (2006). Reliability of 31P-magnetic resonance spectroscopy during an exhaustive incremental exercise test in children.
Eur J Appl Physiol,
98(6), 556-565.
Abstract:
Reliability of 31P-magnetic resonance spectroscopy during an exhaustive incremental exercise test in children.
This study examined the reliability of (31)P-magnetic resonance spectroscopy (MRS) to measure parameters of muscle metabolic function in children. On separate days, 14 children (7 boys and 7 girls) completed three knee-extensor incremental tests to exhaustion inside a whole-body scanner (1.5 T, Phillips). The dynamic changes in the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) and intracellular muscle pH were resolved every 30 s. Using plots of Pi/PCr and pH against power output (W), intracellular thresholds (ITs) for each variable were determined using both subjective and objective procedures. The IT(Pi/PCr) and IT(pH) were observed subjectively in 93 and 81% of their respective plots, whereas the objective method identified the IT(Pi/PCr) in 88% of the plots. The IT(pH) was undetectable using the objective method. End exercise (END) END(Pi/PCr), END(pH), IT(Pi/PCr) and IT(pH) were examined using typical error statistics expressed as a % coefficient of variation (CV) across all three exercise tests. The CVs for the power output at the subjectively determined IT(Pi/PCr) and IT(pH) were 10.6 and 10.3%, respectively. Objective identification of the IT(Pi/PCr) had a CV of 16.3%. CVs for END(pH) and END(Pi/PCr) were 0.9 and 50.0%, respectively. MRS provides a valuable window into metabolic changes during exercise in children. During knee-extensor exercise to exhaustion, END(pH) and the subjectively determined IT(Pi/PCr) and IT(pH) demonstrate good reliability and thus stable measures for the future study of developmental metabolism. However, the objectively determined IT(Pi/PCr) and END(Pi/PCr) displayed poor reliability.
Abstract.
Author URL.
Oliver JL, Williams CA, Armstrong N (2006). Reliability of a field and laboratory test of repeated sprint ability.
Pediatric Exercise Science,
18(3), 339-350.
Abstract:
Reliability of a field and laboratory test of repeated sprint ability
The purpose of this study was to assess the reliability of a field and a laboratory test of repeated sprint ability (RSA). Twelve adolescent boys (15.3 ± 0.3 years) completed five trials of both a field RSA test (7 x 30 m sprints) and a laboratory RSA test (7 x 5 s sprints) performed on a nonmotorized treadmill. Mean coefficients of variation (CV) calculated across all trials were < 2.7% for field sprint times, and, in the laboratory, < 2.9% for velocity and < 8.4% for power output. Fatigue indices (FI) calculated from data in both environments exhibited mean CVs > 23%. The inconsistency in the FIs resulted from the mathematical procedures used in the FI calculation methods. Based on the reliability scores, it was concluded that results obtained from measured performance variables in the field and laboratory, and not calculated FIs, should be used to report RSA. © 2006 Human Kinetics, Inc.
Abstract.
Oliver JL, Williams CA, Armstrong N (2006). The reliability and validity of running tests of repeated sprint ability. Pediatric Exercise Science, 18, 339-350.
Williams CA, Ratel S, Armstrong N (2005). Achievement of peak VO2 during a 90-s maximal intensity cycle sprint in adolescents.
Can J Appl Physiol,
30(2), 157-171.
Abstract:
Achievement of peak VO2 during a 90-s maximal intensity cycle sprint in adolescents.
The aim of this study was to determine whether peak oxygen uptake (PVO2) attained in a 90-s maximal intensity cycle sprint is comparable to that from a conventional ramp test. Sixteen participants (13 boys and 3 girls, 14.6 +/- 0.4 yr) volunteered for the study. On Day 1 they completed a PVO2 test to exhaustion using a 25 W x min(-1) ramp protocol beginning at 50 W. Peak VO2 was defined as the highest VO2 value achieved, and aerobic power (Wmax) as the power output of the final 30 s. On Day 2 the participants completed two 90-s maximal sprints (S1 and S2). A 45-min recovery period separated each sprint. Mean oxygen uptake over the last 10 s of each sprint was determined as PVO2, and minimum power (MinP-30 s) as the mechanical power attained in the final 30 s. A one-way ANOVA was used to analyse differences between S1, S2, and the ramp test for PVO2 and MinP-30 s. Peak VO2 was not significantly different between the ramp, S1, or S2 (2.64 +/- 0.5, 2.49 +/- 0.5, and 2.53 +/- 0.5 L x min(-1), respectively, p > 0.68). The S1 and S2 PVO2 scores represented 91 +/- 10% and 92 +/- 10% of the ramp aerobic test. The MinP-30 s for S1 and S2 were significantly lower than the Wmax of the ramp test, p < 0.05. Hence, for researchers solely interested in PVO2 values, a shorter but more intensive protocol provides an alternative method to the traditional ramp aerobic test.
Abstract.
Author URL.
Ratel S, Williams CAP, Oliver JL, Armstrong N (2005). Effects of Age and Recovery Duration on Performance During Multiple Treadmill Sprints. International Journal of Sports Medicine, 26, 1-8.
Hess TM, Kronfeld DS, Williams CA, Waldron JN, Graham-Thiers P, Greiwe-Crandell K, Lopes MA, Harris PA (2005). Effects of oral potassium supplementation on acid-base status and plasma ion concentrations of horses during endurance exercise.
American Journal of Veterinary Research,
66(3), 466-473.
Abstract:
Effects of oral potassium supplementation on acid-base status and plasma ion concentrations of horses during endurance exercise
Objective - to compare effects of oral supplementation with an experimental potassium-free sodium-abundant electrolyte mixture (EM-K) with that of oral supplementation with commercial potassium-rich mixtures (EM+K) on acid-base status and plasma ion concentrations in horses during an 80-km endurance ride. Animals - 46 healthy horses. Procedure - Blood samples were collected before the ride; at 21-, 37-, 56-, and 80-km inspection points; and during recovery (ie, 30-minute period after the ride). Consumed electrolytes were recorded. Blood was analyzed for pH, PVCO2, and Hct, and plasma was analyzed for Na+, K+, Cl-, Ca2+, Mg2+, lactate, albumin, phosphate, and total protein concentrations. Plasma concentrations of H+ and HCO3-, the strong ion difference (SID), and osmolarity were calculated. Results - 34 (17 EM-K and 17 EM+K treated) horses finished the ride. Potassium intake was 33 g less and Na+ intake was 36 g greater for EM-K-treated horses, compared with EM+K-treated horses. With increasing distance, plasma osmolarity; H+, Na+, K+, Mg2+, phosphate, lactate, total protein, and albumin concentrations; and PVCO2, and Hct were increased in all horses. Plasma HCO3-, Ca2+, and Cl- concentrations were decreased. Plasma H+ concentration was significantly lower in EM-K-treated horses, compared with EM+K-treated horses. Plasma K+ concentrations at the 80-km inspection point and during recovery were significantly less in EM-K-treated horses, compared with EM+K-treated horses. Conclusions and clinical relevance - Increases in plasma H+ and K+ concentrations in this endurance ride were moderate and unlikely to contribute to signs of muscle fatigue and hyperexcitability in horses.
Abstract.
Carter H, Dekerle J, Brickley G, Williams CAP (2005). Physiological responses to 90 s all out isokinetic sprint cycling in boys and men. Journal of Sports Science and Medicine, 4, 437-445.
Carter H, Dekerle J, Brickley G, Williams CAP (2005). Physiological responses to 90 s all out isokinetic sprint cycling in boys and men. Journal of Sports Science and Medicine, 4, 437-445.
Winsley RJ, Fulford J, Macleod K, Ramos-Ibanez N, Armstrong N, Williams CA (2005). Prediction of Visceral Adipose Tissue
Using Air Displacement Plethysmography in Children. Obesity Research, 13(12), 2048-2051.
Winsley RJ, Fulford J, MacLeod KM, Ramos-Ibanez N, Williams CA, Armstrong N (2005). Prediction of visceral adipose tissue using air displacement plethysmography in children.
Obes Res,
13(12), 2048-2051.
Abstract:
Prediction of visceral adipose tissue using air displacement plethysmography in children.
OBJECTIVE: to determine the ability of air displacement plethysmography (ADP) to predict visceral adipose tissue (VAT) volume in children. RESEARCH METHODS AND PROCEDURES: Fifty-five (33 boys/22 girls) white children 13 to 14 years old were studied. Anthropometric measures were collected for body mass, stature, BMI, and waist-to-hip ratio (WHR), and body fat percentage was estimated from triceps and subscapular skinfolds, bioelectrical impedance analysis, and ADP. VAT volume was determined using magnetic resonance imaging, using a multiple slice protocol at levels L1 to L5. RESULTS: Boys had significantly (p < or = 0.05) less VAT volume than girls [645.1 (360.5) cm(3) vs. 1035.8 (717.3) cm(3)]. ADP explained the greatest proportion of the variance in VAT volume compared with the other anthropometric measures. Multiple regression analysis indicated that VAT volume was best predicted by ADP body fat percentage in boys [r(2) = 0.81, SE of the estimate (SEE) = 160.1, SEE coefficient of variation = 25%] and by WHR and BMI in girls (r(2) = 0.80, SEE = 337.71, SEE coefficient of variation = 33%). DISCUSSION: Compared with the other anthropometric measures, ADP explains the greatest proportion of the variance in VAT volume in children 13 to 14 years old. For boys, ADP is the tool of choice to predict VAT volume, yet using the more simply collected measures of BMI and WHR is recommended for girls. However, large SE of the estimates remained, suggesting that if precision is needed, there is no surrogate for direct imaging of VAT.
Abstract.
Author URL.
Ordakowski-Burk AL, Kronfeld DS, Williams CA, Gay LS, Sklan DJ (2005). Temporal folate status during lactation in mares and growth in foals.
American Journal of Veterinary Research,
66(7), 1214-1221.
Abstract:
Temporal folate status during lactation in mares and growth in foals
Objective - to identify changes in folate status of mares and foals during lactation and growth, respectively. Animals - 20 Thoroughbred mares and foals. Procedures - Pregnant mares, and following foaling the same mares with their foals, were maintained on mixed grass-legume pasture and fed either a traditional dietary supplement rich in sugar and starch (SS) or a dietary supplement high in fat and fiber (FF). Blood samples were collected monthly from mares and foals up to 6 months after foaling. Total folate concentration in feed and forage was determined. Analyses of plasma folate, RBC folate, plasma homocysteine (HCY), and milk folate concentrations were performed. Results - Mare plasma folate concentrations declined moderately during 6 months of lactation. Mare RBC folate concentrations initially increased after foaling up to 3 months but declined toward the end of the study. Plasma HCY concentration was higher for mares fed the SS supplement, compared with mares fed the FF supplement from foaling to 6 months of lactation. Milk folate concentrations decreased during the first 3 months and then increased. Foal plasma folate initially declined but then increased. Stable concentrations of RBC folate were observed in foals. Plasma HCY concentrations in foals were unaffected by growth during the last 5 months. References range values for plasma folate, RBC folate, milk folate, and plasma HCY concentrations in healthy lactational mares and young growing foals were determined. Conclusions and clinical relevance - Folate status was not impaired in lactating mares and growing foals under the conditions in our study. It appears that folate supplementation is not necessary.
Abstract.
Williams CAP, Ratel S, Armstrong N (2005). The achievement of peak VO2 during a 90 s maximal intensity cycle sprint in adolescent children. Canadian Journal of Applied Physiology, 30(2), 157-171.
Montfort-Steiger V, Williams CA, Armstrong N (2005). The reproducibility of an endurance performance test in adolescent cyclists.
Eur J Appl Physiol,
94(5-6), 618-625.
Abstract:
The reproducibility of an endurance performance test in adolescent cyclists.
The purpose of the study was to measure the reproducibility of a performance test in well-trained adolescent cyclists. Eight male and one female cyclist [mean age 15.7 (0.7) y] participated in the study. Lactate threshold (LT) and peak VO2 were assessed. The performance test was repeated on three separate days and consisted of 30 min of steady state (SS) cycling at 80% of individual LT. Immediately after the SS cycling a time trial (TT) started with the cyclists having to complete a fixed amount of work as fast as possible. Reliability was assessed for the TT with the coefficient of variation (CV) as the (SD/mean)*100 for each participant, intraclass correlation coefficients (ICC) and typical error (SD of the difference in mean /radical2). The group mean (SD) times for the TT were TT1 1889 (306), TT2 1857 (283) and TT3 1953 (279) s respectively. Individual CV varied from 0.25% to 10%. The ICC for TT1/2 and 2/3 were r = 0.78 and 0.93 (P
Abstract.
Author URL.
Williams CA, Kronfeld DS, Hess TM, Saker KE, Waldron JN, Crandell KM, Hoffman RM, Harris PA (2004). Antioxidant supplementation and subsequent oxidative stress of horses during an 80-km endurance race.
Journal of Animal Science,
82(2), 588-594.
Abstract:
Antioxidant supplementation and subsequent oxidative stress of horses during an 80-km endurance race
This study tested the development of oxidative stress and the effects of antioxidant supplementation in an 80-km ride. A precompetition survey revealed that no competitor would participate without vitamin E supplementation; therefore, 46 horses were paired for past performances and randomly assigned to two groups of 23 each for 3 wk of supplementation before the ride. One group (E) was orally supplemented with 5,000 IU of vitamin E per day; the other group (E+C) received that dose of vitamin E plus 7 g/d of vitamin C. Blood samples, temperature, and heart rate were taken the day before the race, at 21 and 56 km during the ride, at completion, and after 20 min of recovery. Plasma was assayed for lipid hydroperoxides, α-tocopherol, total ascorbate, albumin, creatine kinase (CK), and aspartate aminotransferase (AST). Total glutathione and glutathione peroxidase activity were determined in red blood cells and white blood cells. Thirty-four horses completed the race, 12 horses (six in E and six in E+C) did not finish for reasons including lameness, metabolic problems, and rider option. Plasma ascorbate was higher (P = 0.045) in the E+C group than in the E group. Other than ascorbate, neither antioxidant status nor CK and AST activities were affected by supplementation with E+C vs. E. Red blood cell glutathione peroxidase, white blood cell total glutathione, lipid hydroperoxides, CK, and AST increased, and red blood cell total glutathione and white blood cell glutathione peroxidase activity decreased with distance (P < 0.001). Positive correlations were found for plasma lipid hydroperoxides on CK (r = 0.25; P = 0.001) and AST (r = 0.33; P < 0.001). These results establish an association between muscle leakage and a cumulative index of oxidative stress. © 2004 American Society of Animal Science. All rights reserved.
Abstract.
Ratel S, Williams CA, Oliver J, Armstrong N (2004). Effects of age and mode of exercise on power output profiles during repeated sprints.
Eur J Appl Physiol,
92(1-2), 204-210.
Abstract:
Effects of age and mode of exercise on power output profiles during repeated sprints.
The aim of this study was to compare power output profiles during repeated cycling and running sprints in children and adults. On two separate visits, 12 boys [11.7 (0.5) years] and 13 men [22.1 (2.9) years] performed ten consecutive 10-s sprints interspersed with 15-s recovery intervals on a non-motorised treadmill and cycle ergometer. Peak (PPO) and mean (MPO) power outputs were measured during each sprint. Capillary fingertip blood samples were drawn at rest and 3 min after the final sprint to measure lactate accumulation (Delta[La]). PPO and MPO decreased significantly more in adults compared to children over the ten sprints irrespective of the mode of exercise (P0.05, respectively) and adults (-43.3 versus -40.0%, P>0.05, respectively). In contrast, MPO decreased significantly more during running compared to cycling both in children (-28.9 versus -18.7%, P
Abstract.
Author URL.
Ratel S, Lazaar N, Dore E, Baquet G, Williams CA, Berthoin S, Van Praagh E, Bedu M, Duche P (2004). High-intensity intermittent activities at school: Controversies and facts.
Journal of Sports Medicine and Physical Fitness,
44(3), 272-280.
Abstract:
High-intensity intermittent activities at school: Controversies and facts
In comparison to continuous aerobic type activity, little is known about high-intensity intermittent physical activity in children. Repeated short-term high-intensity activities (> maximal aerobic speed and
Abstract.
Ratel S, Duche P, Hautier CA, Williams CAP, Bedu M (2004). Physiological responses during cycling with noncircular “Harmonic” and circular chainrings. European Journal of Applied Physiology, 91, 100-104.
Moore MS, Dodd CJ, Welsman JR, Armstrong N (2004). Short-term appetite and energy intake following imposed exercise in 9- to 10-year-old girls.
Appetite,
43(2), 127-134.
Abstract:
Short-term appetite and energy intake following imposed exercise in 9- to 10-year-old girls.
Short-term effects of different intensities of exercise-induced energy expenditure on energy intake and hunger were compared in 19 girls (10.0 +/- 0.6 years) in three conditions: sedentary, low-intensity exercise and high-intensity exercise. The exercise conditions involved cycling at 50 and 75% of peak oxygen uptake, respectively, but were designed to evoke approximately 1.50 MJ of total expenditure, as estimated from continuously monitored heart rate. A maintenance breakfast of controlled energy intake was provided and ad libitum energy intake was measured at lunch and dinner. Differences in energy intake relative to expenditure, between 09:30 and 17:00, were calculated by subtracting energy expenditure from energy intake (energy difference). Hunger, fullness and prospective consumption were rated before and after meals and exercise sessions. Lunch energy intake was significantly less after low-intensity exercise than after high-intensity exercise. Energy expenditure was greater in the exercise conditions than when sedentary and the energy difference was more positive in the sedentary condition than in each of the exercise conditions. At mid-afternoon, rated prospective consumption was less after the high-intensity exercise. The imposition of energy expenditure through exercise of either low or high intensity resulted in no detectable increase in energy intake in the short term.
Abstract.
Author URL.
Day SH, Williams C, Folland JP, Gohlke P, Williams AG (2004). The acute effects of exercise and glucose ingestion on circulating angiotensin-converting enzyme in humans. European Journal of Applied Physiology, 92(4-5).
Ratel S, Lazaar N, Williams CA, Bedu M, Duché P (2003). Age differences in human skeletal muscle fatigue during high-intensity intermittent exercise.
Acta Paediatrica, International Journal of Paediatrics,
92(11), 1248-1254.
Abstract:
Age differences in human skeletal muscle fatigue during high-intensity intermittent exercise
It has been shown at similar relative work rates that children have higher resistance to fatigue than adults during repeated bouts of high-intensity exercise. This age-related difference in fatigue resistance may be explained by factors including muscle mass, muscle morphology, energy metabolism and neuromuscular activation. Conclusion: During high-intensity intermittent exercise, recovery periods play an important role in limiting fatigue. Age-related differences in fatigue resistance could also be explained by differences in the rates of resynthesis of some energetic substrates and the rates of removal of various muscle metabolites.
Abstract.
S R, N L, CA W, M B, P DX (2003). Age differences in human skeletal muscle fatigue during high-intensity intermittent exercise. Acta Paediatrica, 92(11), 1248-1254.
Williams CA, Dore E, Albaan J, Van Praagh E (2003). Short term power output in 9 year old children: Typical error between ergometers and protocols. Pediatric Exercise Science, 15(3), 302-312.
Williams CAP, Hammond A, Doust JH (2003). Short term power output of females during isokinetic cycling. Isokinetics and Exercise Science, 11, 123-131.
Brickley G, Doust J, Williams CAP (2002). Physiological responses during exercise to exhaustion at critical power. European Journal of Applied Physiology, 88, 146-151.
Hoffman RM, Hess TM, Williams CA, Kronfeld DS, Griewe-Crandell KM, Waldron JE, Graham-Thiers PM, Gay LS, Splan RK, Saker KE, et al (2002). Speed associated with plasma pH, oxygen content, total protein and urea in an 80 km race.
Equine veterinary journal. Supplement(34), 39-43.
Abstract:
Speed associated with plasma pH, oxygen content, total protein and urea in an 80 km race.
To test the hypothesis that endurance performance may be related quantitatively to changes in blood, we measured selected blood variables then determined their reference ranges and associations with speed during an 80 km race. The plan had 46 horses in a 2 x 2 factorial design testing a potassium-free electrolyte mix and a vitamin supplement. Blood samples were collected before the race, at 21, 37, 56 and 80 km, and 20 min after finishing, for assay of haematocrit, plasma pH, pO2, pCO2, [Na+], [K+], [Ca++], [Mg++], [Cl-], lactate, glucose, urea, cortisol, alpha-tocopherol, ascorbate, creatine kinase, aspartate amino transferase, lipid hydroperoxides, total protein, albumin and creatinine, and erythrocyte glutathione and glutathione peroxidase. Data from 34 finishers were analysed statistically. Reference ranges for resting and running horses were wide and overlapping and, therefore, limiting with respect to evaluation of individual horses. Speed correlations were most repeatable, with variables reflecting blood oxygen transport (enabling exercise), acidity and electrolytes (limiting exercise) and total protein (enabling then, perhaps, limiting). Stepwise regressions also included plasma urea concentration (limiting). The association of speed with less plasma acidity and urea suggests the potential for fat adaptation and protein restriction in endurance horses, as found previously in Arabians performing repeated sprints. Conditioning horses fed fat-fortified and protein-restricted diets may not only improve performance but also avoid grain-associated disorders.
Abstract.
Williams CA, Lopes P (2002). The influence of ventilatory control on heart variability in children. Journal of Sport Sciences, 20, 407-415.
Karila C, de Blic J, Waernessyckle S, Benoist M-R, Scheinmann P (2001). Cardiopulmonary Exercise Testing in Children. Chest, 120(1), 81-87.
Williams CAP, Keen P (2001). Isokinetic measurement of maximal muscle power during leg cycling – a comparison of adolescent boys and adult men. Pediatric Exercise Science, 13, 154-166.
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.
Abstract.
Author URL.
Williams CAP, Carter H, Jones AM, Doust JH (2001). Oxygen uptake kinetics during treadmill running in children and adults. Journal of Applied Physiology, 90, 1700-1706.
Williams CA, Kronfeld DS, Staniar WB, Harris PA (2001). Plasma glucose and insulin responses of Thoroughbred mares fed a meal high in starch and sugar or fat and fiber.
Journal of Animal Science,
79(8), 2196-2201.
Abstract:
Plasma glucose and insulin responses of Thoroughbred mares fed a meal high in starch and sugar or fat and fiber
Plasma concentrations of glucose and insulin following a meal were compared in twelve Thoroughbred mares fed a pelleted concentrate (PC), a traditional sweet feed high in sugar and starch (SS), or a feed high in fat and fiber (FF). The feeds had similar DE and CP but differed in fat (19, 32, and 166 g/kg DM, respectively), NDF (199, 185, and 369 g/kg DM, respectively) and nonstructural carbohydrates (574, 645, and 247 g/kg, respectively). Mares were randomly assigned to two groups balanced for foaling date and weight. All mares received PC in late gestation; then, after foaling, one group was fed SS and the other FF for trials in early and late lactation. Mares were placed in stalls and deprived of feed overnight. A series of blood samples was collected via a jugular catheter from 0 (baseline) to 390 min after consumption of 1.82 kg of feed. Plasma was analyzed for glucose and insulin. Baseline values, peak values, and areas under curves (AUC) were compared by ANOVA. Baseline values were 74.7 ± 10.9 mg/dL for glucose and 5.86 ± 1.80 mIU/L for insulin for all diets and stages. Responses to PC did not differ between the two groups (P > 0.34), indicating the groups were metabolically similar. Peak plasma glucose and insulin concentrations were higher (P < 0.001) in the SS group than in the FF group during early and late lactation. Similarly, glucose and insulin AUC were larger (P < 0.003) in SS than in FF during early and late lactation. These results indicate that metabolic fluctuations are moderated by the replacement of sugar and starch with fat and fiber. This replacement may reduce the risk of certain digestive and metabolic disorders that have been linked to feeding meals of grain-based concentrates to pregnant or lactating mares. © 2001 American Society of Animal Science. All rights reserved.
Abstract.
Williams CA, Armstrong N, Powell J (2000). Aerobic responses of prepubertal boys to two modes of training.
Br J Sports Med,
34(3), 168-173.
Abstract:
Aerobic responses of prepubertal boys to two modes of training.
OBJECTIVE: to investigate the effects of two contrasting eight week training programmes on the aerobic performance of 39 prepubescent boys (mean age 10.1 years). METHODS: all boys were volunteer subjects from three city schools and the schools were matched by a health related behaviour questionnaire. All of the boys were assessed as Tanner stage one for genitalia and pubic hair development. Criterion laboratory tests included peak VO2 as assessed by an incremental discontinuous treadmill test to voluntary exhaustion. Submaximal measurements of heart rate, minute ventilation (VE) and VO2 were also recorded during the treadmill test. One of the schools provided the control group (n = 14), and boys from the other schools followed two contrasting training programmes. The first was a sprint interval running programme (n = 12) comprising 10 second and 30 second sprints, and the second a continuous cycle ergometer programme (n = 13) maintaining a heart rate in the range 80-85% of maximum for 20 minutes on a Monark cycle ergometer. After eight weeks training three times a week, the three groups were retested. RESULTS: There were no significant differences in peak VO2 (p>0.05) with training in either of the groups. Neither were there significant changes in any of the submaximal variables VO2, VE, or heart rate (p>0.05). CONCLUSION: the findings of this study indicate that neither eight week sprint interval running nor continuous cycle ergometer training programmes significantly improve maximal or submaximal indicators of the aerobic performance of prepubertal boys.
Abstract.
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,
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
Abstract.
Armstrong N, Welsman JR, Williams CA, Kirby BJ (2000). Longitudinal changes in young people's short-term power output.
Med Sci Sports Exerc,
32(6), 1140-1145.
Abstract:
Longitudinal changes in young people's short-term power output.
PURPOSE: the influences of age, body size, skin-fold thickness, gender, and maturation on the short-term power output of young people were examined using multilevel modelling. METHODS: Subjects were 97 boys and 100 girls, aged 12.2 +/- 0.4 yr at the onset of the study. Sexual maturity was classified according to Tanner's indices of pubic hair. Peak power (PP) and mean power (MP) were determined on two occasions 1 yr apart using the Wingate Anaerobic Test (WAnT). The data were analyzed using multilevel regression modelling. RESULTS: Initial models identified body mass and stature as significant explanatory variables with an additional positive effect of age, which was smaller for girls' MP. A significant gender difference was apparent for both power indices with girls achieving lower values than boys. A significant incremental effect of later maturity (stages 4 and 5 for pubic hair development) was identified for MP only. Subsequent incorporation of sum of two skin-fold thicknesses into the model yielded significant negative parameter estimates for PP and MP and negated both the stature effects and the maturation influence upon MP. CONCLUSION: There are gender differences in the longitudinal growth of performance on the WanT. Regardless of gender differences, body mass and skin-fold thicknesses appear to be the best anthropometric predictors of WAnT determined PP and MP in young people.
Abstract.
Author URL.
Brickley G, Jenkins DJ, Green S, Williams CA, Wishart C, McEinery M, Doust J (2000). Metabolic responses to intermittent exercise using the critical power concept. Journal of Sports Sciences, 18(7), 526-527.
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,
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.
Abstract.
Carter H, Jones AM, Doust JH, Burnley M, Williams CAP, Barstow TJ (2000). The comparison of VO2 kinetics in treadmill running and cycling ergometry. Journal of Applied Physiology, 89, 899-907.
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).
Williams CA (1999). Anaerobic cycling performance of young people. Sport and Medicina, 5, 21-27.
Williams CA, Smith J, Ainsley J (1999). The effects of a physiotherapy intervention programme on children with developmental co-ordination disorder. Association of Paediatric Chartered Physiotherapists, 91, 32-40.
Williams CA, Bale P (1998). Bias and limits of agreement between hydrodensitometry, bioelectrical impedance and skinfold calipers measures of percentage body fat.
Eur J Appl Physiol Occup Physiol,
77(3), 271-277.
Abstract:
Bias and limits of agreement between hydrodensitometry, bioelectrical impedance and skinfold calipers measures of percentage body fat.
Previous research has often used correlations as a statistical method to show agreement; however, this is not a valid use of the statistic. The purpose of this study was to investigate the bias and limits of agreement for three methods of estimating percentage body fat for 117 male and 114 female university athletes: hydrodensitometry (HYD), bioelectrical impedance (BIA) and skinfold calipers (SKF). The mean (SD) percentage body fat for males as assessed by HYD, BIA and SKF methods, respectively, were 13.2 (3.3)%, 14.1, (3.3)% and 13.0 (3.2)%. Female body fat measurements were 22.5 (3.9)%, 23.7 (4.3)% and 23.8 (4.2)%, respectively. Pearson product moment correlations for male and female body fat percentages between the three methods were high, ranging from 0.81 to 0.86 (P < 0.05). However, compared to the criterion measure of body fat percentage (HYD), the magnitude of agreement BIA and SKF revealed a different pattern. The mean absolute difference between HYD and BIA measurements of body fat for males was -0.8 (2.0)% fat, and between HYD and SKF was it was 0.2 (1.7)% fat. The mean absolute difference for females between HYD and BIA was -1.2 (2.5)%; for HYD and SKF it was -1.4 (2.2)%. Compared to the HYD measures for males and females, the BIA and SKF measures were as much as a 3.8% underestimation and a 6.2% overestimation of body fat. This study provides evidence that the strength of a correlation does not indicate agreement between two methods. In future, reliability and validity studies should examine the absolute differences between two variables and calculate limits of agreement around which a practitioner can appreciate the precision of the methodologies.
Abstract.
Author URL.
Armstrong N, Welsman JR, Kirby BJ, Williams CA (1998). LONGITUDINAL CHANGES IN WINGATE ANAEROBIC TEST PERFORMANCE. Medicine & Science in Sports & Exercise, 30(5).
Williams CA (1998). Young people and physical activity - a literature review.
HEALTH EDUCATION RESEARCH,
13(1), 156-157.
Author URL.
Williams CA (1998). Young people and physical activity - Promoting better practice.
HEALTH EDUCATION RESEARCH,
13(1), 157-157.
Author URL.
Williams CA (1997). Children’s and Adolescents’ Anaerobic Performance During Cycle Ergometry. Sports Medicine, 24, 227-240.
WillĂams CA, Singh M (1997). Dynamic trunk strength of Canadian football players, soccer players, and middle to long distance runners.
J Orthop Sports Phys Ther,
25(4), 271-276.
Abstract:
Dynamic trunk strength of Canadian football players, soccer players, and middle to long distance runners.
Muscle strength data for sports which have varying demands on the trunk musculature are needed. The purpose of this study was to measure the trunk strength of three different sports groups of male varsity athletes and a recreationally active but nontrained group. Forty-six athletes (soccer: N = 16, Canadian football: N = 15, and middle and long distance runners: N = 15) and 15 recreationally active subjects were studied. Three consecutive concentric and eccentric contractions through a range of 60 degrees at an angular velocity of 30 degrees per second (0.5236 rad/sec) were performed to measure the strength of the trunk flexors and extensors. Results showed peak concentric and eccentric flexor torque for football and soccer players to be significantly greater than the other two groups (p < or = 0.05). Peak concentric and eccentric extensor torque was significantly greater for football players than runners (p < or = 0.05). Soccer players' eccentric flexor peak torque relative to body mass was significantly greater than runners and the recreationally active subjects (p < or = 0.05). This study compares trunk flexor and extensor data for specific sports populations.
Abstract.
Author URL.
McManus AM, Armstrong N, Williams CA (1997). Effect of training on the aerobic power and anaerobic performance of prepubertal girls.
Acta Paediatr,
86(5), 456-459.
Abstract:
Effect of training on the aerobic power and anaerobic performance of prepubertal girls.
The purpose of this study was to investigate the effects of two, three times a week, 8-week training programmes on the aerobic power and anaerobic performance of 30 prepubescent girls, with a mean age of 9.6 y. Peak oxygen uptake assessed by an incremental discontinuous treadmill test, and peak power in 5 s and mean power over 30 s estimated from a Wingate anaerobic test were used as the criterion measures. Twelve girls trained using a continuous cycle ergometer programme, 11 girls followed a sprint running programme and the control group consisted of 7 girls. Both training groups significantly (p < 0.05) increased their peak oxygen uptake and peak power in 5 s. However, the increase reported here are lower than those generally observed in adolescents following training. The control group demonstrated no significant (p > 0.05) change in either variable. No significant (p > 0.05) changes in mean power over 30 s were observed in any group.
Abstract.
Author URL.
Williams CA, Armstrong N, Eves N, Faulkner A (1996). Peak aerobic fitness of visually impaired and sighted adolescent girls.
Journal of Visual Impairment and Blindness,
90(6), 495-500.
Abstract:
Peak aerobic fitness of visually impaired and sighted adolescent girls
This study compared the aerobic fitness of 10 visually impaired and 10 sighted girls who performed a discontinuous incremental treadmill test to exhaustion. It found that there was no significant difference between the peak oxygen intake of the two groups. The results indicate that visually impaired children can attain aerobic fitness levels similar to those of sighted children.
Abstract.
Williams CA (1994). Child-Adult Anaerobic Performance Differences. British Journal of Physical Education, 25(2).
FOX K, PAGE A, ARMSTRONG N, KIRBY B (1994). DIETARY RESTRAINT AND SELF-PERCEPTIONS IN EARLY ADOLESCENCE.
PERSONALITY AND INDIVIDUAL DIFFERENCES,
17(1), 87-96.
Author URL.
Williams CA, Armstrong N (1993). Test-Retest Reproducibility of Optimised Peak Power Output During Maximal Sprint Pedalling. British Journal of Physical Education, Research Supplement, 13, 12-15.
