Trunk Constraints Increase Knee Joint Kinetics During Sidestep Cutting in Female Athletes: Implications for Anterior Cruciate Ligament Injury Risk

This study investigated the effects of task constraints applied at the trunk and preparatory step on lower-body joint kinetics associated with ACL injury risk during sidestepping in female athletes. Twenty-one trained female athletes performed six sidestep conditions: pre-planned and unplanned sidesteps, each with and without trunk (holding ~ 5–7.5% body mass at chest level) and preparatory-step (ducking under an adjustable rope at eye height) constraints. Relative joint power at the hip, knee, ankle, and entry velocity, and sidestep angle, were analysed using linear mixed models and statistical parametric mapping. In pre-planned sidesteps, trunk constraints significantly increased negative peak knee joint power compared to unconstrained conditions ( p  = 0.02) and increased negative knee joint power during early stance (23–27%, p  < 0.001). Preparatory-step constraints did not alter knee joint power but significantly increased hip joint power relative to trunk-constrained and unconstrained conditions between 23–35% of stance (p < 0.001). Unplanned sidesteps showed no significant kinetic differences among conditions. Implementing trunk constraints during pre-planned sidesteps increases mechanical demands on the knee joint, facilitating progressive overload and enhancing ACL injury resilience. These findings inform practical training strategies to increase tissue capacity and prepare female athletes for high-risk sidestepping scenarios, potentially contributing to effective ACL injury prevention interventions.