Functional data analysis of lower-limb joint kinematics during badminton lunges under fatigue

Fatigue triggered a "top-down" compensatory response: proximal joints stiffened to stabilize, while the ankle enhanced flexibility to compensate. This "proximal-stiffening, distal-mobility" pattern maintained performance but may have redistributed loads, potentially raising the risk of ACL and lateral ankle ligament injuries. These findings help guide fatigue-specific training and injury-prevention strategies.