Targeted hip abductor fatigue alters trunk and lower limb biomechanics during Single-Leg landing

Fatigue of the hip abductor muscles may influence lower limb biomechanics and potentially contribute to anterior cruciate ligament (ACL) injury risk. However, the effects of targeted hip abductor fatigue on trunk, pelvis and lower limb coordination during landing tasks remain unclear. The present study aimed to investigate how targeted hip abductor fatigue alters the biomechanics of the trunk, pelvis, and lower extremity during single-leg landing (SLL). Twenty healthy male recreational athletes performed SLL before and after a targeted hip abductor fatigue protocol. Kinematic and kinetic data were collected using a three-dimensional motion capture system and force plates, with analysis focused on the timing of peak vertical ground reaction force. Following fatigue, participants exhibited increased hip abduction angle and trunk right inclination, as well as decreased hip flexion and external hip abduction moment. Notably, the external knee abduction moment significantly increased post-fatigue, though it remained negative in absolute value. Increased pelvic left rotation was also observed, indicating compensatory adjustments in trunk-pelvis coordination. These adaptations indicate that targeted muscle fatigue induces complex biomechanical responses across the kinetic chain, rather than uniformly increasing injury risk through valgus-prone mechanics. While the observed changes may reflect stabilizing strategies under fatigue, their implications for ACL loading require further clarification. The current study highlights the relevance of considering whole-body biomechanical responses to targeted fatigue and contributes to a more detailed understanding of neuromuscular control during landing. These findings may support the refinement of injury prevention approaches that address segmental coordination under fatigued conditions.