Relationship Between Shank Angular Acceleration, Hamstring Muscle Activation, and Maximum Speed During Treadmill Sprinting

Background/Objective: Torque generated by shank angular acceleration (SAA) has been proposed as a potential risk factor for increased hamstring muscle loading during the swing phase of the running cycle. However, direct evidence supporting this relationship remains unclear. Therefore, this study aimed to examine the relationship between SAA and peak hamstring muscle activation during the swing phase.Methods: Twenty recreational players (six females, fourteen males) were recruited to perform a minimum of three treadmill sprints at maximum speed. Hamstring muscle activation (specifically, semitendinosus and biceps femoris long head) and SAA were recorded using wireless electromyography and inertial measurement units. Spearman’s rank correlation coefficient (rho) was used to analyze the relationship between the SAA, hamstring muscle activation, and maximum speed, with a significance level of 0.05.Results: SAA exhibited peak of flexion and extension values at approximately 30 and 70% of the swing duration, respectively. A strong positive correlation was observed between peak SAA and peak activation of the semitendinosus (p < 0.001, rho > 0.7), whereas no significant correlation was observed between SAA and the peak activation of the biceps femoris long head. Additionally, no significant relationship was observed between SAA and maximum running speed.Conclusion: The effects of SAA varied among different muscles, emphasizing the need for targeted training strategies to prevent injury. Effectively managing excessive SAA may help reduce hamstring muscle overloading during the late swing phase without significantly affecting maximum running speed. These findings may inform clinical decision-making for coaches and players when designing training programs.