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

Purpose This study examines 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.