Adding a weight to constrain the trunk increases knee joint kinetics during sidestep cutting in female athletes.

Sidestep cutting exposes the knee to high multiplanar loads that both challenge tissue capacity and provide an opportunity to develop resilience through progressive exposure. This study investigated task constraints applied at the trunk and preparatory step and changes in 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, and ankle was analysed using statistical parametric mapping. In pre-planned sidesteps, trunk constraints significantly increased energy absorption at the knee during early stance (23-27%, p < 0.001). Preparatory-step constraints did not alter energy absorption at the knee but significantly increased energy generation at the hip relative to trunk-constrained and unconstrained conditions between 23 and 35% of stance (p < 0.001). Unplanned sidesteps showed no kinetic differences among conditions. Implementing trunk constraints during pre-planned sidesteps increases mechanical demands on the knee joint, suggesting these conditions may serve as a useful means to progressively expose athletes to higher joint loads in controlled training environments. These findings inform practical training strategies to increase tissue capacity and prepare female athletes for high-risk sidestepping scenarios, potentially contributing to an increased injury resiliency.