Differences in joint loading during a side-step cutting manoeuvre on different artificial turf infill depths

This study investigated differences in joint loading during a side-step manoeuvre on artificial grass turfs with different infill depths. The kinematics and kinetics of 17 trained male inter-college soccer players performing the manoeuvre were captured using 10 high-speed optical cameras synchronised to a force-platform at sampling frequencies of 250 Hz and 1000 Hz respectively. Significantly larger lateral forces (GRF_xpeak) (p = 0.036), larger anterior/posterior forces (GRF_ypeak) (p = 0.062) and larger vertical forces (GRF_zpeak) (p = 0.390) suggests that turf with greater infill depths may be firmer. This could elicit greater stresses on the lower extremity, thereby increasing the risk of knee ligament injuries. Significant differences were reported only for ankle inversion angle (p = 0.001; ES = 0.74), inversion/eversion ankle moment (p = 0.039; ES = 0.52) and abduction-adduction ankle moment (p = 0.022; ES = 0.79) at GRFz_peak. Lower extremity adaptations to execute the manoeuvre on turf with greater infill depths may have taken place at the ankle rather than the knee. While this change in technique may implicate injuries, greater infill depths can be counter-intuitive where a certain level of hardness in the artificial turf might be necessary which otherwise could affect the athletes' performance and potentially reduce injury risk.