Biomechanical responses to changes in friction on a clay court surface.
OBJECTIVE
To examine the influence of clay court frictional properties on tennis players' biomechanical response.


METHODS
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 m2surface 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-2conditions. No differences in ankle joint kinematics and knee flexion angles were observed. Later peak knee flexion occurred on the 20kgm-2condition 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 20kgm2condition 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.
School of Health Sciences, University of Salford, UK; Exeter Biomechanics Team, Sport and Health Sciences, University of Exeter, UK. Electronic address: C.Starbuck@salford.ac.uk.
Chelsea
C
Starbuck
Exeter Biomechanics Team, Sport and Health Sciences, University of Exeter, UK.
Victoria
V
Stiles
Sports Engineering Research Group, University of Sheffield, Department of Mechanical Engineering, UK.
Daniel
D
Urà
Sports Engineering Research Group, University of Sheffield, Department of Mechanical Engineering, UK.
Matt
M
Carré
Exeter Biomechanics Team, Sport and Health Sciences, University of Exeter, UK.
Sharon
S
Dixon
D000293:Adolescent; D000538:Aluminum Silicates; D000704:Analysis of Variance; D000843:Ankle Joint / Q000502:physiology*; D001696:Biomechanical Phenomena; D000077215:Clay; D017276:Friction; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D035002:Lower Extremity / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D016059:Range of Motion, Articular; D013715:Tennis / Q000502:physiology*; D016474:Weight-Bearing; D055815:Young Adult
D000538:Aluminum Silicates; D000077215:Clay
Injury risks; Kinematics; Loading rate; Lower limb; Sliding