Comparative effects of unilateral, bilateral, and hybrid combined resistance training on straight punch performance in adolescent boxers: a focus on dominant and non-dominant-side adaptations.

INTRODUCTION

This study aimed to compare the differential effects of unilateral, bilateral, and hybrid complex resistance training on straight punch performance in adolescent boxers and to explore the regulatory mechanisms underlying different training modalities on dominant and non-dominant-side motor performance.

METHODS

This study employed a parallel group design with three intervention groups: unilateral resistance training, bilateral resistance training, and hybrid combined training. Twenty-nine right-handed orthodox stance adolescent boxers were recruited and randomly assigned to a unilateral training group (UNI, n = 10), a hybrid training group (UNI + BI, n = 9), or a bilateral training group (BI, n = 10) for an 8-week specialized resistance training intervention. Based on bilateral one-repetition maximum (1RM) test results, unilateral training loads were set at 50% of bilateral 1RM, and bilateral training loads at 85% of bilateral 1RM. The Xsens MTw Awinda inertial motion capture system and GymAware linear sensor were synchronized to measure peak punch speed and sandbag swing linear velocity for the lead hand (non-dominant side) and rear hand (dominant side).

RESULTS

Time main effect analysis revealed that all three training modalities significantly enhanced straight punch performance for both hands (lead hand: p < 0.01; rear hand: p < 0.05). Interaction effect analysis indicated that, for lead hand straight punch performance, the unilateral group (Δ22.3%) and hybrid group (Δ20.1%) exhibited significantly greater peak speed gains than the bilateral group (Δ9.6%, p < 0.05). The main effect of training type did not reach statistical significance (p > 0.05).

CONCLUSION

In complex resistance training, unilateral and hybrid protocols more effectively improve non-dominant-side punching performance, likely due to neuromuscular adaptations driven by unilateral loads selectively activating weak link muscle groups and optimized motor unit recruitment through bilateral-unilateral coordinated training. It is recommended that coaches refine training designs by incorporating unilateral exercises and adjusting load distribution to enhance non-dominant-side performance and bilateral symmetry in adolescent boxers.