Alterations of landing biomechanics from an inclined treadmill running-induced fatigue protocol

Purpose: This study examined the biomechanical effects of running-induced fatigue on the kinematic and kinetic changes of the lower limb during a countermovement jump (CMJ) via analyzing variations in joint biomechanics during landing. Methods: A running-induced fatigue protocol was employed to explore changes in joint angle, moments, stiffness and loading rate during the CMJ landing pre and post-fatigue. Paired-sample t-tests assessed changes in discrete parameters of joint stiffness, loading rates, and time-varying parameters were compared with one-dimensional statistical parametric mapping. Results: Fatigue significantly reduced the range of motion (ROM) during landing, with significant differences in angles, specifically the dorsi-plantar flexion of right ankle, flexion-extension of left hip, rotation of left knee, and adduction-abduction of right knee (P < 0.001). The first loading rate at touchdown decreased by 10%, and the time intervals between the first and second peak and the second and third peak reduced by 40 and 80%, respectively. Joint loading increased and the sagittal joint stiffness of left hip, right knee, and right ankle exhibited significant differences post-fatigue (P < 0.001). Knee joint reduced the flexion angle (P < 0.001) and the load of knee joint (P < 0.001) during post-fatigue, with the role compensated by hip and ankle joints to achieve balance in the lower limb kinetic chain. Conclusions: These findings provide pilot evidence that running fatigue may lead to changes in lower limb joint loadings and provide a scientific foundation for fatigue prediction and injury assessment.