Comparison of Lower Limb Biomechanical Responses to Running-Induced Fatigue Between Rearfoot and Non-Rearfoot Strike Male Amateur Marathon Runners

<i>Purpose:</i> The purpose of this study was to investigate the effects of foot strike patterns and running-induced fatigue on the biomechanical responses of the knee and ankle joints in amateur marathon runners by analyzing the combined effects of these two factors on lower limb joint kinematics, kinetics, and muscle activation characteristics under different conditions. <i>Methods:</i> A total of 26 participants were recruited.13 male amateur marathon runners with habitual non-rearfoot strike and 13 with rearfoot strike patterns underwent mild, moderate and severe running-induced fatigue interventions. Kinematic, ground reaction force and electromyographic data were collected. A two-way analysis of variance was performed in SPSS for statistical analysis. <i>Results:</i> Fatigue level significantly affected knee joint range of motion ( <i>p</i> = 0.023), peak joint moment ( <i>p</i> = 0.003), and joint stiffness ( <i>p</i> = 0.040). The non-rearfoot strike runners exhibited significantly greater ankle joint range of motion ( <i>p</i> < 0.001) and lower peak joint moments ( <i>p</i> < 0.001) compared to rearfoot strike runners. A significant interaction effect between fatigue and foot strike pattern was observed on the Root Mean Square amplitude of the medial gastrocnemius ( <i>p</i> = 0.017) and biceps femoris ( <i>p</i> = 0.021). <i>Conclusions:</i> A significant interaction effect between fatigue and foot strike patterns was observed in Root Mean Square. Given the impact of localized muscle fatigue on joint kinematics and kinetics, the nonrearfoot strike runners may demonstrate intense fatigue-related biomechanical alterations to the knee and ankle joints during the latter stages of long-distance running. These results suggest that understanding foot strike biomechanics under fatigue may inform training and injury prevention.