Relationships between isokinetic knee and shoulder peak strength with maximal punch force in boxing athletes

BACKGROUND: Muscle strength in the upper and lower limbs is a major contributing factor to punch force and is one of the keys to success in boxing. OBJECTIVE: This study aimed to investigate the relationship between knee and shoulder strength and punching force in boxers. METHODS: Twenty-one boxers completed knee flexion, knee extension, shoulder external rotation and internal rotation isokinetic concentric contractions at slow (60 degrees/s) and fast (180 degrees/s) angular velocities. Maximal punch force tests included lead and rear straight arm punching were assessed using a force platform. RESULTS: Pearson's correlation coefficients revealed that knee extension (r = 0.646-0.848) and knee flexion (r = 0.470-0.646) peak torques were moderately to very strongly correlated with maximal punching force in lead and rear arms. The shoulder internal rotation (r = 0.492-0.634) and shoulder external rotation (r = 0.441-0.588) peak torques were moderate to strongly correlated with maximal punching force. Moreover, knee extension peak torques at 60 degrees/s had higher correlation with maximal punching force. In contrast, shoulder internal rotation peak torques at 180 degrees/s had a larger correlation with maximal punching force. CONCLUSIONS: The main findings indicated the importance of the capacity to generate maximum knee extension and rapid shoulder internal rotation strength, contributing to punch force production.