Publications by year
Rice HM, Nunns M, House C, Fallowfield J, Allsopp A, Dixon S (In Press). A narrow bimalleolar width is a risk factor for ankle inversion injury in male military recruits: a prospective study. Clinical Biomechanics
Nunns M, Dixon SJ, Clarke J, carre M (In Press). Boot-insole effects on comfort and plantar loading at the heel and fifth metatarsal during running and turning in soccer. Journal of Sports Sciences
Damm L, Stiles V, Dixon S (In Press). Human-shoe-surface interaction. In Dixon S, Fleming P, James I, Carre M (Eds.) The Science and Engineering of Sport Surfaces, Oxon: Routledge, 135-157.
Stiles VH, Dixon S (In Press). Sports surfaces, biomechanics and injury. In Dixon S, Fleming P, James I, Carre M (Eds.) The Science and Engineering of Sport Surfaces, Oxon: Routledge, 70-97.
Lilley K, Stiles V, Dixon S
(2022). The influence of design variations in footwear medial-lateral support on the running biomechanics of older female runners. PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART P-JOURNAL OF SPORTS ENGINEERING AND TECHNOLOGY
(1), 53-59. Author URL
Warner MB, Wilson DA, Herrington L, Dixon S, Power C, Jones R, Heller MO, Carden P, Lewis CL
(2019). A systematic review of the discriminating biomechanical parameters during the single leg squat. Physical Therapy in Sport
A systematic review of the discriminating biomechanical parameters during the single leg squat
Objective: to determine whether there are common biomechanical parameters when analysing the single leg squat movement to compare pathological and non-pathological groups and whether these parameters are able to effectively distinguish between groups. Methods: Five electronic databases were searched using MESH terms, keywords and phrases across four constructs: squat, biomechanical measures, region of interest, study design. Studies were selected based on inclusion of a quantitative biomechanical measure, compared between a pathological and a non-pathological group, and participants performed a single leg squat movement. Results: Fifteen studies were included and reviewed, where the majority of studies investigated patellofemoral pain. There was considerable variation in the biomechanical outcome measure used to compare between groups. The frontal plane projection angle was the most commonly reported measure. There was considerable variation in the manner in which the single leg squat was performed. Conclusion: Due to variation in how the single leg squat was performed, it was not possible to determine specific biomechanical parameters that distinguish between pathological and non-pathological groups. Frontal plane projection angle appeared to be a parameter that could be effectively utilised. Standardisation of the single leg squat movement is needed to allow comparison between studies of pathological and non-pathological groups. Abstract
Rice H, Fallowfield J, Allsopp A, Dixon S (2019). Altered forefoot function following a military training activity. Gait & Posture, 74, 182-186.
Dixon S, Nunns M, House C, Rice H, Mostazir M, Stiles V, Davey T, Fallowfield J, Allsopp A
(2019). Prospective study of biomechanical risk factors for second and third metatarsal stress fractures in military recruits. Journal of Science and Medicine in Sport
Prospective study of biomechanical risk factors for second and third metatarsal stress fractures in military recruits
Objectives: This prospective study investigated anatomical and biomechanical risk factors for second and third metatarsal stress fractures in military recruits during training. Design: Prospective cohort study. Methods: Anatomical and biomechanical measures were taken for 1065 Royal Marines recruits at the start of training when injury-free. Data included passive range of ankle dorsi-flexion, dynamic peak ankle dorsi-flexion and plantar pressures during barefoot running. Separate univariate regression models were developed to identify differences between recruits who developed second (n = 7) or third (n = 14) metatarsal stress fracture and a cohort of recruits completing training with no injury (n = 150) (p < 0.05). A multinomial logistic regression model was developed to predict the risk of injury for the two sites compared with the no-injury group. Multinomial logistic regression results were back transformed from log scale and presented in Relative Risk Ratios (RRR) with 95% confidence intervals (CI). Results: Lower dynamic arch index (high arch) (RRR: 0.75, CI: 0.63–0.89, p < 0.01) and lower foot abduction (RRR: 0.87, CI: 0.80–0.96, p < 0.01) were identified as increasing risk for second metatarsal stress fracture, while younger age (RRR: 0.78, CI: 0.61–0.99, p < 0.05) and later peak pressure at the second metatarsal head area (RRR: 1.19, CI: 1.04–1.35, p < 0.01) were identified as risk factors for third metatarsal stress fracture. Conclusions: for second metatarsal stress fracture, aspects of foot type have been identified as influencing injury risk. For third metatarsal stress fracture, a delayed forefoot loading increases injury risk. Identification of these different injury mechanisms can inform development of interventions for treatment and prevention. Abstract
Roberts A, Roscoe D, Hulse D, Bennett AN, Dixon S
(2017). Biomechanical differences between cases with chronic exertional compartment syndrome and asymptomatic controls during walking and marching gait. Gait Posture
Biomechanical differences between cases with chronic exertional compartment syndrome and asymptomatic controls during walking and marching gait.
Chronic exertional compartment syndrome is a significant problem in military populations that may be caused by specific military activities. This study aimed to investigate the kinematic and kinetic differences in military cases with chronic exertional compartment syndrome and asymptomatic controls. 20 males with symptoms of chronic exertional compartment syndrome of the anterior compartment and 20 asymptomatic controls were studied. Three-dimensional lower limb kinematics and kinetics were compared during walking and marching. Cases were significantly shorter in stature and took a relatively longer stride in relation to leg length than controls. All kinematic differences identified were at the ankle. Cases demonstrated increased ankle plantarflexion from mid-stance to toe-off. Cases also demonstrated less ankle inversion at the end of stance and early swing phases. Lower ankle inversion moments were observed during mid-stance. The anthropometric and biomechanical differences demonstrated provide a plausible mechanism for the development of chronic exertional compartment syndrome in this population. The shorter stature in combination with the relatively longer stride length observed in cases may result in an increased demand on the anterior compartment musculature during ambulation. The results of this study, together with clinical insights and the literature suggest that the suppression of the walk-to-run stimulus during group marches may play a significant role in the development of chronic exertional compartment syndrome within a military population. The differences in joint angles and moments also suggest an impairment of the muscular control of ankle joint function, such as a reduced effectiveness of tibialis anterior. It is unclear whether this is a cause or consequence of chronic exertional compartment syndrome. Abstract
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Roberts A, Roscoe D, Hulse D, Bennett AN, Dixon S
(2017). Biomechanical differences between cases with suspected chronic exertional compartment syndrome and asymptomatic controls during running. Gait Posture
Biomechanical differences between cases with suspected chronic exertional compartment syndrome and asymptomatic controls during running.
Chronic exertional compartment syndrome (CECS) has been hypothesised, following clinical observations, to be the result of abnormal biomechanics predominantly at the ankle. Treatment of CECS through running re-education to correct these abnormalities has been reported to improve symptoms. However no primary research has been carried out to investigate the movement patterns of those with CECS. This study aimed to compare the running kinematics and muscle activity of cases with CECS and asymptomatic controls. 20 men with bilateral symptoms of CECS of the anterior compartment and 20 asymptomatic controls participated. Barefoot and shod running 3D kinematics and muscle activity of the left and right legs; and anthropometry were compared. Cases displayed less anterior trunk lean and less anterior pelvic tilt throughout the whole gait cycle and a more upright shank inclination angle during late swing (peak mean difference 3.5°, 4.1° and 7.3° respectively). Cases demonstrated greater step length and stance time, although this was not consistent across analyses. There were no consistent differences in Tibialis anterior or Gastrocnemius medialis muscle activity. Cases were heavier (mean difference 7.9kg, p=0.02) than controls with no differences in height (p>0.05) These differences only partially match the clinical observations previously described. However, no consistent differences were found at the ankle joint suggesting that current running re-education interventions which focus on adjusting ankle kinematics are not modifying pathological aspects of gait. The longer step length is a continuing theme in this population and as such may be a key component in the development of CECS. Abstract
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Starbuck C, Stiles V, Urà D, Carré M, Dixon S
(2017). Biomechanical responses to changes in friction on a clay court surface. J Sci Med Sport
Biomechanical responses to changes in friction on a clay court surface.
OBJECTIVES: to examine the influence of clay court frictional properties on tennis players' biomechanical response. DESIGN: Repeated measures. METHODS: Lower limb kinematic and force data were collected on sixteen university tennis players during 10×180° turns (running approach speed 3.9±0.20ms-1) on a synthetic clay surface of varying friction levels. To adjust friction levels the volume of sand infill above the force plate was altered (kg per m2 surface area; 12, 16 and 20kgm-2). Repeated measures ANOVA and Bonferroni's corrected alpha post-hoc analyses were conducted to identify significant differences in lower limb biomechanics between friction levels. RESULTS: Greater sliding distances (ηp2=0.355, p=0.008) were observed for the lowest friction condition (20kgm-2) compared to the 12 and 16kgm-2 conditions. No differences in ankle joint kinematics and knee flexion angles were observed. Later peak knee flexion occurred on the 20kgm-2 condition compared to the 12kgm-2 (ηp2=0.270, p=0.023). Lower vertical (ηp2=0.345, p=0.027) and shear (ηp2=0.396, p=0.016) loading rates occurred for the 20kgm2 condition compared to the 16kgm2. CONCLUSIONS: Lower loading rates and greater sliding distances when clay surface friction was reduced suggests load was more evenly distributed over time reducing players' injury risks. The greater sliding distances reported were accompanied with later occurrence of peak knee flexion, suggesting longer time spent braking and a greater requirement for muscular control increasing the likelihood of fatigue. Abstract
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Nunns M, Stiles V, Fulford J, Dixon S
(2017). Estimated third metatarsal bending stresses are highly susceptible to variations in bone geometry. Footwear Science
Estimated third metatarsal bending stresses are highly susceptible to variations in bone geometry
Background: Third metatarsal stress fractures are relatively common during Royal Marines recruit training; however, their aetiology is poorly understood. Mathematical modelling of the third metatarsal may aid in understanding risk factors for stress fracture, particularly if the influence of footwear on peak bending stresses can be determined. This study built on previous models of metatarsal bending stress by integrating individual metatarsal geometry and gait data. Methods: Data from five males with size 11 (UK) feet were acquired. MRI images were digitised to determine cross-sectional bone parameters. Gait variables included vertical ground reaction forces, plantar pressure and foot orientation. The magnitude and location of peak bending stresses were calculated for barefoot running, before standard issue combat boots and trainers were compared. Findings: Estimated peak compressive, tensile and torsional stresses were greater in combat assault boots than in trainers (p < 0.05) with medium effect sizes but wide confidence intervals. However, differences in bone geometry between individuals had a much greater influence on estimated peak stresses. Interpretation: Results suggest that bone geometry has a greater influence on third metatarsal stress fracture risk than footwear. Future bone stress simulations should account for bone geometry. Further development of the model in a variety of participants should proceed to verify these suggestions. Abstract
Rice H, Fallowfield J, Allsopp A, Dixon S
(2017). Influence of a 12.8-km military load carriage activity on lower limb gait mechanics and muscle activity. Ergonomics
Influence of a 12.8-km military load carriage activity on lower limb gait mechanics and muscle activity.
The high stress fracture occurrence in military populations has been associated with frequent load carriage activities. This study aimed to assess the influence of load carriage and of completing a load carriage training activity on gait characteristics. Thirty-two Royal Marine recruits completed a 12.8-km load carriage activity as part of their military training. Data were collected during walking in military boots, pre and post-activity, with and without the additional load (35.5 kg). Ground contact time, lower limb sagittal plane kinematics and kinetics, and electromyographic variables were obtained for each condition. When carrying load, there was increased ground contact time, increased joint flexion and joint moments, and increased plantar flexor and knee extensor muscle activity. Post-activity, there were no changes to kinematic variables, knee extensor moments were reduced, and there was evidence of plantar flexor muscle fatigue. The observed gait changes may be associated with stress fracture development. Practitioner Summary: This study identified gait changes due to load carriage and after a military load carriage training activity. Such activities are associated with lower limb stress fractures. A pre-post study design was used. Gait mechanics changed to a greater extent when carrying load, than after completion of the activity when assessed without load. Abstract
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Roberts A, Hulse D, Bennett AN, Dixon S
(2017). Plantar pressure differences between cases with symptoms of clinically diagnosed chronic exertional compartment syndrome and asymptomatic controls. Clin Biomech (Bristol, Avon)
Plantar pressure differences between cases with symptoms of clinically diagnosed chronic exertional compartment syndrome and asymptomatic controls.
BACKGROUND: Anterior chronic exertional compartment syndrome of the leg has been hypothesised to develop due to excessive muscle activity and foot pronation. Plantar pressure variables related to lower limb muscle activity and foot type may therefore provide insight into this condition. METHODS: 70 male cases and 70 asymptomatic controls participated. A clinical diagnosis was established from typical symptoms, with clinical examination excluding other pathologies. Plantar pressure variables during walking, hypothesised to be related to foot type, toe extensor activity or had shown predictive validity for general exercise-related lower leg pain, were extracted. FINDINGS: Cases were shorter in height (mean difference 2.4cm), had greater body mass (mean difference 4.4kg) and had reduced ankle dorsiflexion range of motion than controls (mean difference 1.5cm). Plantar pressure variables indicative of foot-type and toe extensor activity did not differ between groups (P>0.05). The magnitude of medial forefoot loading was the strongest plantar pressure predictor of the presence of chronic exertional compartment syndrome (Odds ratio:0.87, P=0.005). There was also some evidence of greater lateral heel loading at 5% of stance time (P=0.049-0.054). INTERPRETATION: the lack of association with foottype-related and toe extensor activity-related plantar pressure variables suggest that these are not risk factors for the development of chronic exertional compartment syndrome, contrary to earlier hypotheses. The greater lateral to medial loading could theoretically represent increased Tibialis anterior muscle activity at heel strike but a subsequent loss of control as the ankle is lowered. Future studies directly investigating muscle activity and function are now required. Abstract
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Nunns MPI, Dixon SJ, Clarke J, Carré M
(2016). Boot-insole effects on comfort and plantar loading at the heel and fifth metatarsal during running and turning in soccer. J Sports Sci
Boot-insole effects on comfort and plantar loading at the heel and fifth metatarsal during running and turning in soccer.
Plantar loading may influence comfort, performance and injury risk in soccer boots. This study investigated the effect of cleat configuration and insole cushioning levels on perception of comfort and in-shoe plantar pressures at the heel and fifth metatarsal head region. Nine soccer academy players (age 15.7 ± 1.6 years; height 1.80 ± 0.40 m; body mass 71.9 ± 6.1 kg) took part in the study. Two boot models (8 and 6 cleats) and two insoles (Poron and Poron/gel) provided four footwear combinations assessed using pressure insoles during running and 180° turning. Mechanical and comfort perception tests differentiated boot and insole conditions. During biomechanical testing, the Poron insole generally provided lower peak pressures than the Poron/gel insole, particularly during the braking step of the turn. The boot model did not independently influence peak pressures at the fifth metatarsal, and had minimal influence on heel loads. Specific boot-insole combinations performed differently (P Abstract
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Nunns MP, House CM, Rice H, Mostazir M, Davey P, Stiles V, Fallowfield J, Allsopp A, Dixon SJ
(2016). Four biomechanical and anthropometric measures predict tibial stress fracture:. A prospective study of 1065 Royal Marines. British Journal of Sports Medicine
Four biomechanical and anthropometric measures predict tibial stress fracture:. A prospective study of 1065 Royal Marines
Background: Tibial stress fractures cause a significant burden to Royal Marines recruits. No prospective running gait analyses have previously been performed in military settings. Abstract
Aim: We aimed to identify biomechanical gait factors and anthropometric variables associated with increased risk of TSF.
Methods: 1065 Royal Marines recruits were assessed in week-2 of training. Bilateral plantar pressure and 3D lower limb kinematics were obtained for barefoot running at 3.6 m.s-1, providing dynamic arch index, peak heel pressure and lower limb joint angles. Age, bimalleolar breadth, calf girth, passive hip internal/external range of motion and body mass index (BMI) were also recorded. Ten recruits who sustained a TSF during training were compared with 120 recruits who completed training injury-free using a binary logistic regression model to identify injury risk factors.
Results: Four variables significantly (p
Moore IS, Jones AM, Dixon SJ
(2016). Reduced oxygen cost of running is related to alignment of the resultant GRF and leg axis vector: a pilot study. Scand J Med Sci Sports
Reduced oxygen cost of running is related to alignment of the resultant GRF and leg axis vector: a pilot study.
This pilot study investigated whether a 10-week running program (10wkRP), which reduced the oxygen cost of running, affected resultant ground reaction force (GRF), leg axis alignment, joint moment characteristics, and gear ratios. Ten novice, female runners completed a 10wkRP. Running kinematics and kinetics, in addition to oxygen consumption ( V ˙ O 2 ) during steady-state running, were recorded pre- and post-10wkRP. V ˙ O 2 decreased (8%) from pre-10wkRP to post-10wkRP. There was a better alignment of the resultant GRF and leg axis at peak propulsion post-10wkRP compared with pre-10wkRP (10.8 ± 4.9 vs 1.6 ± 1.2°), as the resultant GRF vector was applied 7 ± 0.6° (P = 0.008) more horizontally. There were shorter external ankle moment arms (24%) and smaller knee extensor moments (23%) at peak braking post-10wkRP. The change in V ˙ O 2 was associated with the change in alignment of the resultant GRF and leg axis (rs = 0.88, P = 0.003). As runners became more economical, they exhibited a more aligned resultant GRF vector and leg axis at peak propulsion. This appears to be a self-optimization strategy that may improve performance. Additionally, changes to external ankle moment arms indicated beneficial low gear ratios were achieved at the time of peak braking force. Abstract
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Low DC, Dixon SJ
(2016). The influence of shock-pad density and footwear cushioning on heel impact and forefoot loading during running and turning movements. INTERNATIONAL JOURNAL OF SURFACE SCIENCE AND ENGINEERING
(1), 86-99. Author URL
Starbuck C, Damm L, Clarke J, Carré M, Capel-Davis J, Miller S, Stiles V, Dixon S
(2016). The influence of tennis court surfaces on player perceptions and biomechanical response. J Sports Sci
The influence of tennis court surfaces on player perceptions and biomechanical response.
This study aimed to examine player perceptions and biomechanical responses to tennis surfaces and to evaluate the influence of prior clay court experience. Two groups with different clay experiences (experience group, n = 5 and low-experience group, n = 5) performed a 180° turning movement. Three-dimensional ankle and knee movements (50 Hz), plantar pressure of the turning step (100 Hz) and perception data (visual analogue scale questionnaire) were collected for two tennis courts (acrylic and clay). Greater initial knee flexion (acrylic 20. 8 ± 11.2° and clay 32.5 ± 9.4°) and a more upright position were reported on the clay compared to the acrylic court (P Abstract
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Dixon S, Fleming P, James I, Carré M (2015). Introduction: History and development of sports surfaces.
Dixon S, Fleming P, James I, Carré M (2015). Preface.
Dixon S, Fleming P, James I, Carré M (2015). The future of sports surfaces. In (Ed) The Science and Engineering of Sport Surfaces, 179-186.
Dixon S, Fleming P, James I, Carré M
(2015). The science and engineering of sport surfaces.
The science and engineering of sport surfaces
Moore IS, Dixon SJ
(2014). Changes in sagittal plane kinematics with treadmill familiarization to barefoot running. Journal of Applied Biomechanics
Changes in sagittal plane kinematics with treadmill familiarization to barefoot running
Interest in barefoot running and research on barefoot running are growing. However a methodological issue surrounding investigations is how familiar the participants are with running barefoot. The aim of the study was to assess the amount of time required for habitually shod runners to become familiar with barefoot treadmill running. Twelve female recreational runners, who were experienced treadmill users, ran barefoot on a treadmill for three bouts, each bout consisting of 10 minutes at a self-selected speed with 5 minute rest periods. Sagittal plane kinematics of the hip, knee, ankle, and foot during stance were recorded during the first and last minute of each 10-minute bout. Strong reliability (ICC >. 8) was shown in most variables after 20 minutes of running. In addition, there was a general trend for the smallest standard error of mean to occur during the same period. Furthermore, there were no significant differences in any of the biomechanical variables after 20 minutes of running. Together, this suggests that familiarization was achieved between 11 and 20 minutes of running barefoot on a treadmill. Familiarization was characterized by less plantar flexion and greater knee flexion at touchdown. These results indicate that adequate familiarization should be given in future studies before gait assessment of barefoot treadmill running. Abstract
Ura D, Carré MJ, Starbuck C, Dixon SJ
(2014). Effect of varying the volume infill sand on synthetic clay surfaces in terms of the shoe-surface friction. Procedia Engineering
Effect of varying the volume infill sand on synthetic clay surfaces in terms of the shoe-surface friction
The friction developed by the shoe-surface interface on artificial clay has not been widely studied, and can influence player's performance and injury risk. The aim of this research was to investigate the effect of varying the quantity of infill sand on shoesurface friction on an artificial clay court tennis surface. A laboratory-based mechanical test rig was used to measure the friction force developed at the shoe-surface interface. Additionally, the perception of a group of participants, performing a turning movement on the same surface under dry conditions, was collected in order to compare against the mechanical results. The relationship between the normal force and friction generated by the shoe-surface interaction was examined for surfaces with different sand in-fill volumes. The mechanical testing was performed under dry and wet conditions, showing strong and significant differences. Results indicated that the normal force significantly influenced the static and dynamic frictional forces. For lower sand infill volumes, as normal loading increased, the dry condition was found to exhibit the lowest peak static friction force and highest average dynamic friction force. However, for higher sand infill volume conditions, the opposite behaviour was observed. Strong and significant positive linear relationships were found between peak friction force and average dynamic friction force for all infill sand volumes and conditions. The mechanical results were in agreement with the perception data, which suggests that the participants were sensitive to the small changes in sand infill volumes. The findings of this study will therefore aid the understanding of tennis players' perceived response to a tennis court surface. In order to get a better understanding of friction behaviour, further testing needs to be performed, and once the mechanisms involved are understood, surface properties could be modified to increase performance and reduce injury risk. © 2014 Elsevier Ltd. Abstract
Moore IS, Pitt W, Nunns M, Dixon S (2014). Effects of a seven-week minimalist footwear transition programme on footstrike modality, pressure variables and loading rates. Footwear Science
Carré MJ, Clarke JD, Damm L, Dixon SJ
(2014). Friction at the tennis shoe-court interface: How biomechanically informed lab-based testing can enhance understanding. Procedia Engineering
Friction at the tennis shoe-court interface: How biomechanically informed lab-based testing can enhance understanding
This paper presents some of the methodology, observations and findings from a 30-month study, aiming to improve the understanding of tennis shoe-court interactions and the biomechanical implications of changes in friction between the shoe and surface. A detailed programme of biomechanical player testing on different court surfaces provided the boundary conditions with which to develop a lab-based rig capable of simulating the key aspects of shoe-surface interaction that are required for acceptable performance (e.g. push-off to accelerate) within expected levels of consistency (e.g. for a controlled slide). Largescale parametric testing could then be carried out for a variety of surface types and components under a range of loading conditions, without the risk of injury to human participants. Two case studies are described to demonstrate the value of a combined approach of biomechanical field testing and lab-based rigs that simulate shoe-court interactions. These include a study that compared different artificial clay court designs; and a study that examined the effect of different acrylic hard court parameters on friction and the tribological mechanisms that explain the observed interaction © 2014 Elsevier Ltd. Abstract
Moore IS, Jones AM, Dixon SJ
(2014). Relationship between metabolic cost and muscular coactivation across running speeds. Journal of Science and Medicine in Sport
Relationship between metabolic cost and muscular coactivation across running speeds
Objectives: Muscular coactivation can help stabilise a joint, but contrasting results in previous gait studies highlight that it is not clear whether this is metabolically beneficial. The aim was to assess the relationship between the metabolic cost of running and muscular coactivation across different running speeds, in addition to assessing the reliability and precision of lower limb muscular coactivation. Design: Eleven female recreational runners visited the laboratory on two separate occasions. On both occasions subjects ran at three speeds (9.1, 11 and 12kmh-1) for six minutes each. Methods: Oxygen consumption and electromyographic data were simultaneously recorded during the final two minutes of each speed. Temporal coactivations of lower limb muscles during the stance phase were calculated. Five muscles were assessed: rectus femoris, vastus lateralis, biceps femoris, tibialis anterior and gastrocnemius lateralis. Results: Nonparametric correlations revealed at least one significant, positive association between lower limb muscular coactivation and the metabolic cost of running for each speed. The length of tibialis anterior activation and muscular coactivation of the biceps femoris-tibialis anterior and gastrocnemius lateralis-tibialis anterior decreased with speed. Conclusions: These results show that longer coactivations of the proximal (rectus femoris-biceps femoris and vastus lateralis-biceps femoris) and leg extensor (rectus femoris-gastrocnemius lateralis) muscles were related to a greater metabolic cost of running, which could be detrimental to performance. The decrease in coactivation in the flexor and distal muscles at faster speeds occurs due to the shorter duration of tibialis anterior activation as speed increases, yet stability may be maintained. Abstract
Moore IS, Jones AM, Dixon SJ
(2014). Relationship between metabolic cost and muscular coactivation across running speeds. J Sci Med Sport
Relationship between metabolic cost and muscular coactivation across running speeds.
OBJECTIVES: Muscular coactivation can help stabilise a joint, but contrasting results in previous gait studies highlight that it is not clear whether this is metabolically beneficial. The aim was to assess the relationship between the metabolic cost of running and muscular coactivation across different running speeds, in addition to assessing the reliability and precision of lower limb muscular coactivation. DESIGN: Eleven female recreational runners visited the laboratory on two separate occasions. On both occasions subjects ran at three speeds (9.1, 11 and 12 km h(-1)) for six minutes each. METHODS: Oxygen consumption and electromyographic data were simultaneously recorded during the final two minutes of each speed. Temporal coactivations of lower limb muscles during the stance phase were calculated. Five muscles were assessed: rectus femoris, vastus lateralis, biceps femoris, tibialis anterior and gastrocnemius lateralis. RESULTS: Nonparametric correlations revealed at least one significant, positive association between lower limb muscular coactivation and the metabolic cost of running for each speed. The length of tibialis anterior activation and muscular coactivation of the biceps femoris-tibialis anterior and gastrocnemius lateralis-tibialis anterior decreased with speed. CONCLUSIONS: These results show that longer coactivations of the proximal (rectus femoris-biceps femoris and vastus lateralis-biceps femoris) and leg extensor (rectus femoris-gastrocnemius lateralis) muscles were related to a greater metabolic cost of running, which could be detrimental to performance. The decrease in coactivation in the flexor and distal muscles at faster speeds occurs due to the shorter duration of tibialis anterior activation as speed increases, yet stability may be maintained. Abstract
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Damm L, Starbuck C, Stocker N, Clarke J, Carré M, Dixon S
(2014). Shoe-surface friction in tennis: Influence on plantar pressure and implications for injury. Footwear Science
Shoe-surface friction in tennis: Influence on plantar pressure and implications for injury
Purpose: the different strategies employed by tennis players as a result of changes in friction properties of the playing surface are likely to influence injury incidence. Lower risk of injuries on surfaces that allow sliding has been reported. The aim of the present study was to characterise in-shoe pressure during tennis specific movements performed on a hard court and artificial clay in two surface-specific shoes. Methods: Two tennis surfaces were compared: artificial clay and cushioned acrylic hard court. Participants wore two different pairs of court-specific shoes on each surface. Seven (five males, two females) competitive tennis players performed three movements - open stance forehand, forehand plant (incorporated into a drill) and side jump. In-shoe plantar pressure distribution was recorded using the Pedar (Novel, Munich) insole system. Results: Significantly lower mean and peak pressure were measured during the side jump and running forehand plant on clay compared to hard court. Running forehand plant on artificial clay was characterised by a longer step duration and larger number of unloading episodes than on acrylic. Footwear did not influence peak pressures. Conclusions: a change in surface has a greater effect on plantar pressures than a change in shoe. The higher pressures on a hard court support an association for increased levels of overuse injuries. On clay, limiting areas of high pressure and a longer braking step could facilitate sliding by preventing sticking. Unloading episodes could also be part of the strategy aiming at sliding on clay. These differences are relevant to understand surface-specific mechanisms of injuries. Abstract
Moore IS, Jones A, Dixon S (2014). The pursuit of improved running performance: can changes in cushioning and somatosensory feedback influence running economy and injury risk?. Footwear Science
Moore IS, Jones A, Dixon S
(2014). The pursuit of improved running performance: can changes in cushioning and somatosensory feedback influence running economy and injury risk?. Footwear Science
The pursuit of improved running performance: can changes in cushioning and somatosensory feedback influence running economy and injury risk?
There is currently no consensus regarding the effect that barefoot (BFT) running has on running economy (RE). Stride length and shoe mass are confounding variables, with a BFT stride length being shorter than a shod (SH) stride length. Comparison of SH, minimalist shod (MS) and BFT allows controlled variation of cushioning and somatosensory feedback to determine the effect that either and/or both have on RE and running mechanics. Methods: Fifteen female habitually shod, recreational runners visited the laboratory twice. Familiarisation with BFT and SH treadmill running occurred during visit one, in addition to determining SH stride length and BFT stride length. During visit two participants ran BFT, SH and MS with BFT stride length and MS with SH stride length at 10 km·h-1 for six minutes with 10-minute rest periods between each condition. Lower limb kinematics, electromyography, impact acceleration and O2 were recorded during the final two minutes of each run. Results: BFT RE was significantly better than SH and MS with BFT stride length. SHRE was significantly worse than MS with SH stride length, but similar to MS with a BFT stride length. Low vertical oscillation, peak eversion and peak dorsiflexion, less plantarflexion at toe-off, in addition to an earlier occurrence of heel off, higher impact accelerations and greater tibialis anterior activity were observed during the most economical condition. Conclusions: Heightened somatosensory feedback and lack of cushioning (BFT) offered an advantage to economy over less somatosensory feedback (MS) and cushioning (SH). Whilst the low vertical oscillation and low plantarflexion at toe-off appear to contribute to the improved RE, other changes to running mechanics whilst BFT could potentially influence injury risk. © 2014 © 2014 Taylor & Francis. Abstract
Low DC, Dixon SJ
(2014). Understanding the Effect of Changes to Natural Turf Hardness on Lower Extremity Loading. MEASUREMENT & CONTROL
(7), 212-218. Author URL
Damm L, Clarke J, Carré M, Dixon S (2013). Biomechanical and mechanical testing of non-sliding and sliding tennis surfaces. Footwear Science, 5(SUPPL. 1).
Nunns M, House C, Fallowfield J, Allsopp A, Dixon S
(2013). Biomechanical characteristics of barefoot footstrike modalities. J Biomech
Biomechanical characteristics of barefoot footstrike modalities.
Barefoot running has increased in popularity over recent years, with suggested injury risk and performance benefits. However, despite many anecdotal descriptions of barefoot running styles, there is insufficient evidence regarding the specific characteristics of barefoot running. The present study provided reference data for four footstrike modalities adopted across a large cohort of habitually shod male runners while running barefoot: heel strikers (HS), midfoot strikers (MS), forefoot strikers (FS) and a newly defined group, toe runners (TR - contact made only with the forefoot), compared with the three modalities previously reported. Plantar pressure analysis was used for the classification of footstrike modality, with clearly distinguishable pressure patterns for different modalities. In the present study, the distribution of footstrike types was similar to that previously observed in shod populations. The absence of differences in ground contact time and stride length suggest that potential performance benefits of a non-HS style are more likely to be a function of the act of running barefoot, rather than of footstrike type. Kinematic data for the knee and ankle indicate that FS and TR require a stiffer leg than HS or MS, while ankle moment and plantar pressure data suggest that a TR style may put greater strain on the plantar-flexors, Achilles tendon and metatarsal heads. TR style should therefore only be adopted with caution by recreational runners. These findings indicate the importance of considering footstrike modality in research investigating barefoot running, and support the use of four footstrike modalities to categorise running styles. Abstract
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Rice H, Nunns M, House C, Fallowfield J, Allsopp A, Dixon S
(2013). High medial plantar pressures during barefoot running are associated with increased risk of ankle inversion injury in Royal Marine recruits. Gait Posture
High medial plantar pressures during barefoot running are associated with increased risk of ankle inversion injury in Royal Marine recruits.
BACKGROUND: Ankle inversion injury is common in military populations but associated biomechanical risk factors are largely unknown. This prospective study examined the association between pressure and kinematic variables, and ankle inversion injury risk in Royal Marine (RM) recruits. It was hypothesised that a more medially concentrated pressure at the heel-off phase of stance, greater impulse and peak pressure at the first metatarsal head, greater peak rearfoot eversion angle and greater eversion excursion would be associated with ankle inversion injury. METHODS: Data from 145 male, injury-free RM recruits were recorded in week-2 of a 32-week military training programme. Each recruit completed five running trials at 3.6 ms(-1), along a 2m pressure plate. Kinematic data were simultaneously recorded. Injuries sustained during the training programme were prospectively recorded. FINDINGS: Data from eleven recruits who had suffered an ankle inversion injury during RM training were compared with 20 uninjured controls. The injury group displayed a higher (P Abstract
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Clarke J, Carre MJ, Damm L, Dixon S
(2013). The development of an apparatus to understand the traction developed at the shoe-surface interface in tennis. PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART P-JOURNAL OF SPORTS ENGINEERING AND TECHNOLOGY
(3), 149-160. Author URL
Clarke J, Dixon SJ, Damm L, Carré MJ
(2013). The effect of normal load force and roughness on the dynamic traction developed at the shoe-surface interface in tennis. Sports Engineering
The effect of normal load force and roughness on the dynamic traction developed at the shoe-surface interface in tennis
During tennis-specific movements, such as accelerating and side stepping, the dynamic traction provided by the shoe-surface combination plays an important role in the injury risk and performance of the player. Acrylic hard court tennis surfaces have been reported to have increased injury occurrence, partly caused by increased traction that developed at the shoe-surface interface. Often mechanical test methods used for the testing and categorisation of playing surfaces do not tend to simulate loads occurring during participation on the surface, and thus are unlikely to predict the human response to the surface. A traction testing device, discussed in this paper, has been used to mechanically measure the dynamic traction force between the shoe and the surface under a range of normal loading conditions that are relevant to real-life play. Acrylic hard court tennis surfaces generally have a rough surface topography, due to their sand and acrylic paint mixed top coating. Surface micro-roughness will influence the friction mechanisms present during viscoelastic contacts, as found in footwear-surface interactions. This paper aims to further understand the influence micro-roughness and normal force has on the dynamic traction that develops at the shoe-surface interface on acrylic hard court tennis surfaces. The micro-roughness and traction of a controlled set of acrylic hard court tennis surfaces have been measured. The relationships between micro-roughness, normal force, and traction force are discussed. © 2013 the Author(s). Abstract
Damm L, Low D, Richardson A, Clarke J, Carré M, Dixon S
(2013). The effects of surface traction characteristics on frictional demand and kinematics in tennis. Sports Biomech
The effects of surface traction characteristics on frictional demand and kinematics in tennis.
The interaction between footwear and surfaces influences the forces experienced by tennis players. The purpose of this study was to investigate traction demand and kinematic adaptation during tennis-specific movements with changes in traction characteristics of surfaces. We hypothesised that players would increase the utilised coefficient of friction (horizontal to vertical ground reaction force ratio) when the shoe surface combination had a high coefficient of friction and flex their knee after contact to facilitate braking. Eight participants performed two separate movements, side jump out of stance and running forehand. Ground reaction force was measured and three-dimensional kinematic data were recorded. Clay surface and cushioned acrylic hard court (low vs. high shoe-surface friction) were used. The peak utilised coefficient of friction was greater on clay than the hard court. The knee was less flexed at impact on clay (-5.6 +/- 10.2 degrees) and at peak flexion (-13.1 +/- 12.0 degrees) during the running forehand. Our results indicate that tennis players adapt the level ofutilised friction according to the characteristics of the surface, and this adaptation favours sliding on the low friction surface. Less knee flexion facilitates sliding on clay, whereas greater knee flexion contributes to braking on the hard court. Abstract
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Lilley K, Stiles VH, Dixon S
(2013). The influence of motion control shoes on the running gait of mature and young females. Gait and Posture
The influence of motion control shoes on the running gait of mature and young females
This study compared the running gait of mature and young females, and investigated the effect of a motion control shoe. First, it was hypothesised that in a neutral shoe, mature females would display significantly greater rearfoot eversion, knee internal rotation and external adductor moments when compared to a younger group. Secondly, the motion control shoe would reduce rearfoot eversion and knee internal rotation in both groups. Thirdly it was hypothesised that the motion control shoe would increase knee external adductor moment, through an increase in knee varus and moment arm.
15 mature (40–60 years) and 15 young (18–25 years) females performed 10 running trials at 3.5 m s−1 ± 5% over a force platform. Two shoes were tested, the Adidas Supernova Glide (neutral), and the Adidas Supernova Sequence (motion control). Ankle and knee joint dynamics were analysed for the right leg, and the mean of ten trials was calculated. Joint moments were calculated using inverse dynamics.
In the neutral condition, mature females presented greater peak rearfoot eversion, knee internal rotation, and external adductor moments than young females (p < 0.05). A motion control shoe significantly reduced peak rearfoot eversion and knee internal rotation among both groups (p < 0.05). No between shoe differences in knee external adductor moment were observed.
A motion control shoe is recommended to reduce risk of injury associated with rearfoot eversion and knee internal rotation in mature females. However since the knee external adductor moment is a variable commonly associated with medial knee loading it is suggested that alternative design features are required to influence this moment.
Moore IS, Jones AM, Dixon SJ
(2012). Mechanisms for improved running economy in beginner runners. Med Sci Sports Exerc
Mechanisms for improved running economy in beginner runners.
UNLABELLED: Controversy surrounds whether running mechanics make good predictors of running economy (RE) with little known about the development of an economical running gait. PURPOSE: the aim of this study was to identify if mechanical or physiological variables changed during 10 wk of running in beginners and whether these changes could account for any change in RE. METHODS: a 10-wk running program (10 wkRP) was completed by 10 female beginner runners. A bilateral three-dimensional kinematic and kinetic analysis, in addition to RE and lower body flexibility measurements, was performed before and after the 10 wkRP. The Balke-Ware graded walking exercise test was performed before and after the 10 wkRP to determine VO2max. RESULTS: Seven kinematic and kinetic variables significantly changed from before to after training, in addition to a significant decrease in calf flexibility (27.3° ± 6.3° vs 23.9° ± 5.6°, P < 0.05). A significant improvement was seen in RE (224 ± 24 vs 205 ± 27 mL · kg(-1) · km(-1), P < 0.05) and treadmill time to exhaustion (16.4 ± 3.2 vs 17.3 ± 2.8 min, P < 0.05); however, VO2max remained unchanged from before to after training (34.7 ± 5.1 vs 34.3 ± 5.6 mL · kg(-1) · min(-1)). Stepwise regression analysis showed three kinematic variables to explain 94.3% of the variance in change in RE. They were a less extended knee at toe off (P = 0.004), peak dorsiflexion occurring later in stance (P = 0.001), and a slower eversion velocity at touchdown (P = 0.042). The magnitude of change for each variable was 1.5%, 4.7%, and 34.1%, respectively. CONCLUSIONS: These results show that beginner runners naturally developed their running gait as they became more economical runners. Abstract
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Nunns M, Stiles V, Dixon S
(2012). The effects of standard issue Royal Marine recruit footwear on risk factors associated with third metatarsal stress fractures.
The effects of standard issue Royal Marine recruit footwear on risk factors associated with third metatarsal stress fractures
Clarke J, Carré M, Damm L, Dixon S
(2012). The influence of surface characteristics on the tribological interactions at the shoe-surface interface in tennis. Procedia Engineering
The influence of surface characteristics on the tribological interactions at the shoe-surface interface in tennis
During dynamic tennis specific movements, such as accelerating and side stepping, the traction provided by a shoe-surface combination plays an important role in the injury risk and performance of the player. Acrylic hard court tennis surfaces have been reported to have increased injury occurrence due to an increased traction coefficient. There is a requirement for an improved scientific understanding of the tribological interactions at the shoe surface interface and the effects footwear and surface parameters have on the friction mechanism developed. Often mechanical test methods used for the testing and categorisation of playing surfaces do not tend to simulate loads occurring during participation on the surface, and thus are unlikely to predict human response to the surface. A new traction testing device, discussed in this paper, has been developed to mechanically measure the traction force between the shoe and the surface under appropriate loading conditions. Acrylic Harcourt tennis surfaces generally have a rough surface topography, due to a sand and acrylic paint mixed top coating, and have a deformable under layer to provide impact attenuation. Surface micro-roughness has been found to influence the friction mechanisms presents during viscoelastic contacts, as found in footwear-surface interactions. This paper aims to further understand the influence of micro-roughness on tennis surfaces. The micro-roughness and traction of a controlled set of acrylic hard court tennis surfaces have been measured. The influence of roughness on tennis surfaces traction is discussed. © 2012 Published by Elsevier Ltd. Abstract
Clarke J, Carre M, Damm L, Dixon S
(2012). Understanding the influence of surface roughness on the tribological interactions at the shoe-surface interface in tennis. PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY
(J7), 636-647. Author URL
Lilley K, Stiles V, Dixon SJ
(2011). A Biomechanical Comparison of the Running Gait of Mature and Young Females. Gait and Posture
A Biomechanical Comparison of the Running Gait of Mature and Young Females
Background. Due to health and social advantages, the popularity of running as a sport among mature female runners is expanding steadily. However, the incidence of running injuries and associated conditions is vast among this group. The purpose of this study was to quantify gait parameters of mature and younger female runners to assess whether certain running characteristics predispose to debilitating conditions. It was hypothesised that mature females would exhibit greater rearfoot eversion, knee internal rotation, knee external adductor moments and loading rate of ground reaction force when compared to younger runners. Methods. 15 mature (40-60 years) and 15 young (18-24 years) females performed 10 running trials at 3.5 m.s-1 in the biomechanics laboratory. Both kinematic and ground reaction force data were collected. Signs of osteoarthritis and knee injuries were assessed using the KOOS scale. Findings. Mature females produced significantly higher peak rearfoot eversion, knee internal rotation, external adductor moment and loading rate of ground reaction force. compared to the young participants (p"lt;0.05). Interpretations. Although all participants recorded “symptom free” on the KOOS scale, all variables of gait found higher among the mature group have previously been associated with development of overuse injuries and debilitating conditions, suggesting a possible predisposition towards these conditions among the mature group. Abstract
Stiles VH, Guisasola IN, James IT, Dixon SJ
(2011). Biomechanical Response to Changes in Natural Turf during Running and Turning. Journal of Applied Biomechanics
Biomechanical Response to Changes in Natural Turf during Running and Turning
The present study integrated biomechanical and engineering assessments to determine how humans responded to variations in turf during running and turning. Ground reaction force (AMTI, 960 Hz) and kinematic data (Vicon Peak, automatic opto-electronic system, 120 Hz) were collected in the laboratory from eight participants performing running (3.83 m.s-1) and turning trials (10/condition) on three different natural turf conditions. Mechanical measures of surface hardness (Clegg Hammer) and shear strength (cruciform Shear Vane) were taken before and after participant testing. A RM-ANOVA revealed that 5th MTP impact velocity (horizontal and resultant) during turning was significantly lower on the natural turf surface that possessed significantly harder properties (after participant testing) and the greatest resistance to shear failure both before and after participant testing (p Abstract
Clarke J, Carré M, Richardson A, Yang Z, Damm L, Dixon S
(2011). Understanding the traction of tennis surfaces. Procedia Engineering
Understanding the traction of tennis surfaces
The traction provided by a footwear-surface interaction can have an impact on player safety, performance and overall enjoyment of sport. Mechanical test methods used for the testing and categorisation of safe playing surfaces do not tend to simulate loads occurring during participation on the surface, and thus are unlikely to predict human response to the surface. For example, the pendulum system routinely employed by the International Tennis Federation (I.T.F.) utilises a standard rubber 'foot', rather than a shoe sole, and does not apply forces comparable to those in real play. There is a requirement for an improved scientific understanding of the tribological interactions at the shoe surface interface and the effects footwear and surface parameters have on the traction mechanism developed. The relationship between normal force and the coefficient of traction for the forefoot of a tennis shoe in contact with different tennis surfaces was examined using a bespoke traction rig. The effects of surface roughness were also examined. A power relationship was found between normal force and traction. As normal force increased differences in surface traction were found. The normal force, stiffness, and roughness of the surfaces affected the adhesive and hysteresis friction mechanisms that contribute to the overall traction force. © 2011 Published by Elsevier Ltd. Abstract
Fleming P, Young C, Dixon S, Carre M
(2010). Athlete and coach perceptions of technology needs for evaluating running performance. Sports Engineering
Athlete and coach perceptions of technology needs for evaluating running performance
Athletes and their support team utilise technology to measure and evaluate technique and athletic performance. Existing techniques for motion and propulsion measurement and analysis include a combination of indirect methods (high-speed video) and direct methods (force plates and pressure systems). These methods are predominantly limited to controlled laboratory environments (in a small area relative to the competition environment), require expert advice and support, and can take significant time to evaluate the data. Consequently, the more advanced measurement techniques are considered to be restricted to specific coaching sessions, or periods in the year leading up to competition, when the time and expertise of further support staff are available. The more widely used, and simple, devices for monitoring ‘performance’ during running include stopwatches, GPS tracking and accelerometer-based systems to count strides. These provide useful information on running duration, distance and velocity but lack detailed information on many key aspects of running technique. In order to begin the process of development of more innovative technologies for routine use by athletes and coaches, a study was required to improve the understanding of athletes’ and coaches’ perception of their requirements from measurement technology. This study outlines a systematic approach to elicit and evaluate their perceptions, and presents the findings from interviews and a questionnaire. The qualitative data are presented as a hierarchical graphical plot (structured relationship model) showing six general dimensions (technique, footwear and surface, environment, performance, injury and cardiovascular) and shows the development of these general dimensions from the interviewee quotations. The questionnaire quantitative data enhances the study by further ranking characteristics that arise from the interviews. A contrast is shown between short and longer distance runner groups, as might be expected. The current technology available to elite runners is briefly reviewed in relation to the 22 characteristics identified as important to measure. The conclusions highlight the need for newer technologies to measure aspects of running style and performance in a portable and integrated manner, with suggestions as to size and weight likely to be acceptable to users for emerging devices. Abstract
Guisasola I, James I, Stiles V, Dixon S
(2010). Dynamic behaviour of soils used for natural turf sports surfaces. Sports Engineering
Dynamic behaviour of soils used for natural turf sports surfaces
The modulus and damping properties of soils in compression are a function of soil type, water content, stress history and loading rate. To model human–surface interaction with natural turf sports surfaces, stiffness and damping properties must be determined at dynamic loading rates. Two contrasting soil types, a Sand and a Clay Loam, commonly used in sports surfaces were loaded uniaxially to 2 kN at loading rates between 0.6 and 6 kN s−1 in modified dynamic soil testing apparatus. Soils were compacted prior to loading but initial cycles resulted in viscoplastic deformation, with strain accumulation with repeated cycles of loading. Ultimately a resilient, viscoelastic steady-state equilibrium with loading was established. Resilient modulus and damping ratio varied with soil type, water content, stress history and increased significantly with loading rate. The resilient modulus of the Sand soil, typical of modern free-draining sand construction natural turf sports surfaces, was significantly greater than that of a Clay Loam soil more characteristic of traditional natural turf surfaces; reducing water content caused an increase in modulus and a decrease in damping ratio in the Clay Loam soil. Determination of these properties provides initial data for the modelling natural turf surface behaviour in terms of both ball and human interactions, with further research required to determine the effect of both grass roots and leaves on mechanical behaviour. Abstract
Low DC, Dixon SJ
(2010). Footscan pressure insoles: accuracy and reliability of force and pressure measurements in running. Gait Posture
Footscan pressure insoles: accuracy and reliability of force and pressure measurements in running.
In the current investigation, the accuracy and reliability of two pairs of Footscan pressure insoles (500 Hz, RSscan, Belgium) was assessed, with four female (pair 1) and four male (pair 2) participants each performing 16 running trials (3.8m/s ± 5%). Intraclass Correlation Coefficients (ICC) revealed that the reliability of the force and pressure data was generally excellent (ICC>0.75). In comparison with impact and propulsive force data collected simultaneously with a force plate (AMTI, 500 Hz), insole data were significantly lower (p Abstract
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Dixon SJ, Hinman RS, Creaby MW, Kemp G, Crossley KM
(2010). Knee joint stiffness during walking in knee osteoarthritis. Arthritis Care and Research
Knee joint stiffness during walking in knee osteoarthritis
To investigate the construct validity of walking knee stiffness as a measure to differentiate between individuals with and without knee osteoarthritis (OA) and the construct validity of walking knee stiffness as related to self-reported knee stiffness. The contributors to walking stiffness and its relationship with loading rate and adduction moment are also investigated.
Thirty-seven individuals with knee OA and 11 asymptomatic controls participated. Knee stiffness was calculated during walking as the change in knee flexion-extension moment divided by the change in knee flexion angle. Forward-stepwise regression models and Pearson's correlation coefficients were used to evaluate the relationships between variables.
Knee stiffness in walking was significantly greater in the OA group (mean ± SD 10.1 ± 4.4 Nm/°/kg × 100) compared with the controls (mean ± SD 5.6 ± 1.5 Nm/°/kg × 100) (P < 0.001). Knee excursion range explained 39% of the variance in walking knee stiffness (B = -0.736, P < 0.001) and knee extensor moment a further 7% (B = 6.974, P = 0.045). In the OA group, walking knee stiffness was not associated with self-reported stiffness (r = 0.029; P = 0.863). For the OA group, greater self-reported stiffness was associated with lower peak knee adduction moment (B = -0.354, P < 0.001).
The construct validity of walking knee stiffness is supported. The poor correlation between walking stiffness and self-reported stiffness suggests the 2 measures evaluate different aspects of knee stiffness. Since a measure of walking stiffness is likely to provide valuable information, future research evaluating its clinical significance is merited.
Guisasola I, James I, Llewellyn C, Stiles V, Dixon S
(2010). Quasi-static mechanical behaviour of soils used for natural turf sports surfaces and stud force prediction. Sports Engineering
Quasi-static mechanical behaviour of soils used for natural turf sports surfaces and stud force prediction
The quasi-static testing of soils used in natural turf pitches yields key parameters in soil modelling,including elastic moduli, Poisson’s ratio and Mohr–Coulomb parameters for shearing resistance and cohesion in soil. The bulk strength of a Sand soil used in the construction of elite sports surfaces was found to increase initially and then decrease with increasing water content due to apparent cohesion effects. For a Clay Loam soil, Abstract
more common in recreational facilities, shear strength decreased with water content. Reducing density resulted in a reduction of shear strength and elastic moduli in both soils due to reduced packing of particles reducing particle–particle contact surface area. The effect of roots on the shear strength of a Sand soil was not significant but reduced elastic moduli significantly. Horizontal forces measured during running and turning in a biomechanics laboratory were in good agreement with forces predicted using a simple quasi-static soil model for coarse-grained (Sand) soils although this was not the case with the Clay Loam soil.
Stiles VH, James IT, Dixon SJ, Guisasola IN
(2009). Natural turf surfaces: the case for continued research. Sports Med
Natural turf surfaces: the case for continued research.
It is well documented that health and social benefits can be attained through participation in sport and exercise. Participation, particularly in sports, benefits from appropriate surface provisions that are safe, affordable and high quality preferably across the recreational to elite continuum. Investment, construction and research into artificial sports surfaces have increased to meet this provision. However, not all sports (e.g. golf, rugby and cricket) are suited to training and match-play on artificial turf without compromising some playing characteristics of the games. Therefore, full sport surface provision cannot be met without the use of natural turf surfaces, which also have an important role as green spaces in the built environment. Furthermore, a significant number of people participate in outdoor sport on natural turf pitches, although this is a declining trend as the number of synthetic turf surfaces increases. Despite natural turf being a common playing surface for popular sports such as soccer, rugby and cricket, few biomechanical studies have been performed using natural turf conditions. It is proposed that if natural turf surfaces are to help meet the provision of sports surfaces, advancement in the construction and sustainability of natural turf surface design is required. The design of a natural turf surface should also be informed by knowledge of surface-related overuse injury risk factors. This article reviews biomechanical, engineering, soil mechanics, turfgrass science, sports medicine and injury-related literature with a view to proposing a multidisciplinary approach to engineering a more sustainable natural turf sport surface. The present article concludes that an integrated approach incorporating an engineering and biomechanical analysis of the effects of variations in natural turf media on human movement and the effects of variations in human movement on natural turf is primarily required to address the longer-term development of sustainable natural turf playing surfaces. It also recommends that the use of 'natural turf' as a catch-all categorization in injury studies masks the spatial and temporal variation within and among such surfaces, which could be important. Abstract
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Wood LE, Dixon SJ, Grant C, Armstrong N (2008). Age and gender differences in isokinetic elbow flexion and extension torque development in children. International Journal of Sports Medicine, 29, 466-470.
Creaby MW, Dixon SJ
(2008). External frontal plane loads may be associated with tibial stress fracture. Med Sci Sports Exerc
External frontal plane loads may be associated with tibial stress fracture.
PURPOSE: the role of applied external loads in tibial stress fracture is poorly understood. The purpose of this study was to determine whether the magnitude and angle of frontal and sagittal force vectors and the magnitude of the free moment of ground reaction force (the torsional moment between the foot and the ground) during running gait differ between military recruits with and without a history of tibial stress fracture. METHODS: Ten male military recruits with tibial stress fracture history and 20 matched controls performed shod running trials over a force plate. The magnitude and the direction of the frontal and sagittal plane ground reaction force, in addition to the free moment, were compared between the groups. RESULTS: the frontal plane force vector was directed significantly more medially in the stress fracture group during midstance and late stance (P < 0.05). The magnitude of frontal and sagittal plane ground reaction forces and the free moment were not higher in the stress fracture group compared with controls. CONCLUSION: These data highlight differences in the direction with which external forces in the frontal plane are applied in military recruits with a history of tibial stress fracture. These differences may be important in the development of the injury. Abstract
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Dixon SJ, Creaby MW, Hinman RS, Kemp G, Crossley KM
(2008). Functional knee joint stiffness in medial tibiofemoral osteoarthritis. Author URL
Dixon SJ, James IT, Low D (2008). Influence of footwear and soil density on loading within the shoe and soil surface during running. Journal of Sports Engineering and Technology, 222(P1), 1-10.
Dixon SJ, McNally K
(2008). Influence of orthotic devices prescribed using pressure data on lower extremity kinematics and pressures beneath the shoe during running. Clin Biomech (Bristol, Avon)
Influence of orthotic devices prescribed using pressure data on lower extremity kinematics and pressures beneath the shoe during running.
BACKGROUND: Orthotic devices are frequently prescribed as a conservative treatment of lower extremity injury. The purpose of this study was to investigate the influence of orthotic devices prescribed using pressure data on lower extremity movement and loading patterns. METHODS: Twenty-two subjects ran barefoot over a pressure plate for the prescription of orthotic devices. The influence of the prescribed orthoses on lower extremity kinematics and pressure beneath the shoe was assessed by collection of data for 10 running trials with a neutral shoe and 10 with the addition of the orthotic device. For each running trial, initial and peak angles were determined for rearfoot inversion-eversion, lower leg internal rotation, ankle dorsi-plantar flexion, knee flexion and rearfoot eversion velocity. In addition, the relative pressure on the lateral side to medial side of the shoe (pressure balance) was determined by dividing the foot into areas of medial and lateral heel and five metatarsals. Peak lateral and medial heel and foot balance were determined during early stance to indicate differences in balance during this phase. FINDINGS: the orthotic devices resulted in a significant reduction in peak eversion and eversion velocity and a significant increase in the initial inversion angle (P Abstract
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Wood LE, Dixon S, Grant C, Armstrong N
(2008). Isokinetic elbow torque development in children. International Journal of Sports Medicine
Isokinetic elbow torque development in children
The aim of this study was to examine age and gender differences in isokinetic eccentric (ECC) elbow flexion (EF) and extension (EE) torques in children. Thirty-seven children participated in a 3-year longitudinal study. The average age ± SD at the first test occasion was 13.0 ± 0.3 years. Isokinetic ECC EF and EE torques at 0.52 rad·s-1, MRI determined muscle cross-sectional areas (CSAs), stature, and arm length were determined annually. Concentric (CON) EF and EE torques for the same children reported previously, enabled functional torque ratios (ECC antagonist/CON agonist) to be calculated . In contrast to isokinetic EF torques, ECC EE torques were not significantly higher than CON EE torques (across test occasions and for boys and girls). Functional torque ratios did not significantly differ with age or between boys and girls. Multilevel modelling was used to examine age and gender effects once differences in body/muscle size had been considered. ECC EF torque was relatively greater in girls following adjustment for size. These data contribute to the understanding of differences in upper body strength performance and injury propensity during growth and maturation, suggesting CON and ECC torque development are muscle and gender specific. © Georg Thieme Verlag KG Stuttgart. Abstract
Stiles VH, Dixon SD, Guisasola IN, James IT
(2008). Kinematic response to variations in natural turf during running. Author URL
(2008). Use of pressure insoles to compare in-shoe loading for modern running shoes. Ergonomics
Use of pressure insoles to compare in-shoe loading for modern running shoes.
The primary objective of this paper was to compare in-shoe loading for different models of running shoe using measurements of force distribution. It was hypothesised that a shoe designed with minimal focus on cushioning would demonstrate significantly higher peak forces and rates of loading than running shoes designed with cushioning midsoles. Loading was compared using in-shoe peak forces for six footwear conditions. It was found that peak rate of loading at the heel provided clear distinctions between shoes. In support of the study hypothesis, the shoe with minimal focus on cushioning had a significantly higher rate of loading than all but one of the other test shoes. Data collected for midfoot and forefoot areas of the foot highlighted the importance of considering loading across the foot surface. The results of the present study demonstrate that pressure insoles provide a useful tool for the assessment of loading across the foot plantar surface for different footwear conditions. There are numerous models of running shoe for individuals to select from, with limited information available regarding the performance of the shoes during running. The current study demonstrates differences in loads across the foot plantar surface during running, indicating differences in performance for different footwear models. Abstract
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Stiles VH, Dixon SJ (2007). Biomechanical response to systematic changes in impact interface cushioning while performing a tennis specific movement. Journal of Sport Sciences, 25(11), 1229-1239.
VStil, Dixon SJ (2007). Biomechanical response to systematic changes in impact interface cushioning while performing a tennis specific movement .
Wood LE, Dixon SJ, Grant C, Armstrong N (2007). Elbow flexor strength, muscle size and moment arms in pre-pubertal children. Paediatric Exercise Science, 18, 457-469.
(2007). Influence of a commercially available orthotic device on rearfoot eversion and vertical ground reaction force when running in military footwear. Mil Med
Influence of a commercially available orthotic device on rearfoot eversion and vertical ground reaction force when running in military footwear.
The objective of this study was to investigate the influence of a commercially available orthotic device on rearfoot movement and peak impact force variables during running in combat assault boots. Eight military trainees performed running trials under two running conditions: boot with standard-issue insole and boot with the test orthotic. For each trial, vertical ground reaction force and frontal plane rearfoot angle data were collected. It was found that peak eversion angle was not significantly influenced by the orthotic device (p > 0.05), but that this peak occurred later in stance (p < 0.05). Peak impact force, average rate of loading, and peak rate of loading of impact force were all lower when the orthotic device was used (p < 0.05). The findings of this study highlight the potential of a commercially available orthotic to provide benefits more typically associated with molded prescription orthoses, providing a cost-effective option to the routine use of prescription orthotic devices. Abstract
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Stiles VH, Dixon SJ, James IT
(2006). An Initial Investigation of Human-Natural Turf Interaction in the Laboratory. ISEA 2006 Conference on Engineering of Sport 6.
An Initial Investigation of Human-Natural Turf Interaction in the Laboratory
Dixon SJ (2006). Application of centre of pressure to indicate rearfoot inversion-eversion in shod running. Journal of the American Podiatric Medical Association, 96(4), 305-312.
Dixon SJ, Allsopp A, Creaby MW (2006). Comparison of static and dynamic biomechanical measures in military recruits with and without a history of third metatarsal stress fracture. Clinical Biomechanics, 21(4), 412-419.
Wood LE, Dixon S, Grant C, Armstrong N
(2006). Elbow flexor strength, muscle size, and moment arms in prepubertal boys and girls. PEDIATRIC EXERCISE SCIENCE
(4), 457-469. Author URL
Stiles VH, Dixon SJ
(2006). The influence of different playing surfaces on the biomechanics of a tennis running forehand foot plant. J Appl Biomech
The influence of different playing surfaces on the biomechanics of a tennis running forehand foot plant.
Research suggests that heightened impacts, altered joint movement patterns, and changes in friction coefficient from the use of artificial surfaces in sport increase the prevalence of overuse injuries. The purposes of this study were to (a) develop procedures to assess a tennis-specific movement, (b) characterize the ground reaction force (GRF) impact phases of the movement, and (c) assess human response during impact with changes in common playing surfaces. In relation to the third purpose it was hypothesized that surfaces with greatest mechanical cushioning would yield lower impact forces (PkFz) and rates of loading. Six shod volunteers performed 8 running forehand trials on each surface condition: baseline, carpet, acrylic, and artificial turf. Force plate (960 Hz) and kinematic data (120 Hz) were collected simultaneously for each trial. Running forehand foot plants are typically characterized by 3 peaks in vertical GRF prior to a foot-off peak. Group mean PkFz was significantly lower and peak braking force was significantly higher on the baseline surface compared with the other three test surfaces (p Abstract
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Dixon SJ, Collop AC, Batt ME (2005). Compensatory adjustments in lower extremity kinematics in response to a reduced cushioning of the impact interface in heel-toe running. Sports Engineering, 8, 47-56.
Dixon SJ (2005). Diagnostic assessment of preparedness of level one sports science students for biomechanics modules. International Journal of Mathematics Education in Science and Technology, 36, 49-64.
Wood LE, Dixon S, Grant C, Armstrong N
(2004). Elbow flexion and extension strength relative to body or muscle size in children. Medicine and Science in Sports and Exercise
Elbow flexion and extension strength relative to body or muscle size in children
Purpose: the purpose of this study was to examine gender- and age-related differences in elbow flexion and extension strength in children, when linear size measurements and actual measurements of muscle size were used as explanatory variables in a multilevel model. Methods: Thirty-seven children participated in a 3-yr longitudinal study (18 boys and 19 girls). The average age ± SD at the first test occasion was 13.0 ± 0.3 yr. Stature, arm length, isokinetic concentric and isometric elbow extension and flexion torques, and MRI-determined elbow flexor and extensor muscle cross-sectional areas (CSAs) were assessed annually. Multilevel modeling was used to describe the relationship between the measured torques and body/muscle size variables, incorporating age, age by gender, and gender as additional explanatory variables. Results: When muscle CSA was included in the static and dynamic torque multilevel models, gender differences in strength were nonsignificant. In contrast, use of stature or arm length alone, suggested gender differences in strength that could not be explained by differences in body size. All torque measures were best explained by inclusion of muscle CSA and a linear dimension in the models. Age also explained additional variance in torque, but the influence of age was action and muscle specific. Conclusion: Use of only linear dimensions rather than muscle CSA to account for differences in size may have clouded our understanding of strength development in children. Abstract
Wood LE, Dixon SJ, Grant C, Armstrong N (2004). Strength Relative to Body or Muscle Size in Children. Medicine and Science in Sports and Exercise, 36, 1977-1984.
House CM, Dixon SJ, Allsopp AJ
(2004). User trial and insulation tests to determine whether shock-absorbing insoles are suitable for use by military recruits during training. Military Medicine
User trial and insulation tests to determine whether shock-absorbing insoles are suitable for use by military recruits during training
A user trial was undertaken to determine whether a shock-absorbing insole is suitable for military use. Two thicknesses of insole (3 mm and 6 mm) were studied and were issued to 38 Royal Marine recruits to wear in their military boots for weeks 12 to 30 of training. Biomechanical measurements showed that both thicknesses of insole significantly (p < 0.05) attenuated the peak pressures generated at heel strike and during forefoot loading when new (relative to a no-insole condition) and that this was well maintained after wear. This was supported by mechanical tests conducted on the insoles. It was concluded that the insoles are sufficiently durable for military use. The main user complaint was that water retention reduced the comfort of the insoles; however, insulation tests conducted with a foot manikin indicated that switching from the current-issue Saran insoles to the trial insoles would not increase the risk of recruits sustaining nonfreezing cold injuries to their feet. Abstract
Dixon SJ, House CM, Smith CV, Waterworth C (2003). Biomechanical analysis of ground contact when running in military boots with new and degraded insoles. Medicine & Science in Sports & Exercise, 35(3), 472-479.
Dixon SJ, Stiles VH (2003). Shoe-surface interaction in tennis. Sports Engineering, 6(1), 1-10.
Dixon SJ, Turrell JK
(2002). Relationship between rearfoot movement and medial forces during barefoot running. Author URL
Waterworth, C. Allsop, A.J. House, C.M. (2002). The influence of simulated wear upon the ability of insoles to reduce peak pressures during running when wearing military boots. Gait and Posture, 16(3), 297-303.
Dixon SJ, Kerwin DG (2002). Variations in Achilles Tendon Loading with Heel Intervention in Heel-Toe Runners. Journal of Applied Biomechanics, 18, 321-331.
Dixon SJ, Collop AC, Batt ME
(2000). Surface effects on ground reaction forces and lower extremity kinematics in running. Med Sci Sports Exerc
Surface effects on ground reaction forces and lower extremity kinematics in running.
INTRODUCTION: Although running surface stiffness has been associated with overuse injuries, all evidence to support this suggestion has been circumstantial. In the present study, the biomechanical response of heel-toe runners to changes in running surface has been investigated. METHODS: Six heel-toe runners performed shod running trials over three surfaces: a conventional asphalt surface, a new rubber-modified asphalt surface, and an acrylic sports surface. The surfaces were categorised according to impact absorbing ability using standard impact test procedures (BS 7044). RESULTS: the rubber-modified asphalt was found to exhibit the greatest amount of mechanical impact absorption, and the conventional asphalt the least. The comparison of peak impact force values across surfaces for the group of subjects demonstrated no significant differences in magnitude of force. However, a significant reduction in loading rate of peak impact force was detected for the rubber-modified surface compared with conventional asphalt (P < 0.1). Although analysis of group data revealed no significant differences in kinematic variables when running on the different surfaces, a varied response to surface manipulation among runners was demonstrated, with marked differences in initial joint angles, peak joint angles, and peak joint angular velocities being observed. DISCUSSION: for some subjects, the maintenance of similar peak impact forces for different running surfaces was explained by observed kinematic adjustments. For example, when running on the surface providing the least impact absorption, an increased initial knee flexion was observed for some subjects, suggesting an increased lower extremity compliance. However, for some subjects, sagittal plane kinematic data were not sufficient for the explanation of peak impact force results. It appears that the mechanism of adaptation varies among runners, highlighting the requirement of individual subject analyses. Abstract
. Author URL
Dixon SJ, Collop AC, Batt ME (2000). The importance of running surface on the biomechanical assessment of sports shoes.
Dixon SJ, Batt ME, Collop AC
(1999). Artificial playing surfaces research: a review of medical, engineering and biomechanical aspects. International Journal of Sports Medicine
Artificial playing surfaces research: a review of medical, engineering and biomechanical aspects
In this paper, current knowledge of artificial playing surfaces is reviewed. Research status in the fields of sports medicine, engineering and biomechanics is described. A multidisciplinary approach to the study of artificial sports surface properties is recommended. The development of modelling techniques to characterise fundamental material properties is described as the most appropriate method for the unique specification of material properties such as stiffness and damping characteristics. It is suggested that the systematic manipulation of fundamental surface material properties in biomechanics research will allow the identification of subject responses to clearly defined surface variation. It is suggested that subjects should be grouped according to characteristic behaviour on specific sports surfaces. It is speculated that future biomechanics research will identify subject criterion related to differing group responses. The literature evidence of interactions between sports shoes and sports surfaces leads to the suggestion that sports shoe and sports surface companies should work together in the development of ideal shoe - surface combinations for particular groups of subjects. Abstract
Dixon SJ, Kerwin DG
(1999). The influence of heal lift manipulation on sagittal plane kinematics in running. Journal of Applied Biomechanics
The influence of heal lift manipulation on sagittal plane kinematics in running
In this study, sagittal plane joint angles of the lower extremity were used to obtain an indication of the influence of heel lift manipulation on Achilles tendon strain in running. The influence of increased heel lift on lower extremity kinematics was investigated for 8 heel striking subjects. With increased heel lift, all subjects demonstrated reductions in peak ankle dorsi-flexion and consistent values of peak knee flexion, indicating that there were reductions in peak Achilles tendon strain. Group analysis demonstrated that the reductions in peak ankle angle were statistically significant (p Abstract