Knee and ankle biomechanics in 90° side cutting on synthetic turf with shock pad

Abstract

The purpose of this study was to examine differences in knee and ankle biomechanics on synthetic turf with and without a shock pad in two approach velocities during a 90° cutting movement. Twelve recreational male American football or soccer players performed five trials of 90° side cutting in each of four conditions: turf only and turf with shock pad at approach velocity of 3.0 and 4.0 m/s. A two-way (surface × approach velocity) ANOVA was used to analyse selected variables. Knee and ankle variables were generally similar across surface conditions. However, peak knee frontal-plane loading eccentric power was greater (p = 0.013) while peak knee frontal-plane push-off eccentric power was reduced on the shock pad (p = 0.020). A surface × approach velocity interaction was detected for peak knee sagittal-plane eccentric power (p = 0.018), and a post-hoc analysis found a significant increase of peak knee sagittal-plane eccentric power at a faster approach speed on the turf only condition compared to the turf with the shock pad. There were increases in the knee extension moments (p = 0.004), peak push-off medial ground reaction force (GRF, p = 0.025), peak ankle eversion moment (p < 0.001), and ankle inversion ROM (p = 0.001) as approach velocity increased while peak push-off vertical GRF decreased (p = 0.011). The effects of the inclusion of a shock pad on lower extremity loading during a 90° cutting movement are limited. The results indicate that the turf with the shock pad absorbs more kinetic energy as speed increases than the turf alone.