The biceps brachii role in the stabilization of the cross punch

Purpose: starting from an injury background, we assumed that the biceps brachii’s activations could have an important role in upper limbs injury. In this work we analyzed whether different activations of the biceps brachii impact on the power transfer of the punch and how boxers of different skill levels activate the biceps brachii when deliver a punch according to their skill level and efficacy. Methods: we enrolled, basing on official rankings, 23 skilled (n=6) and unskilled boxers. Subjects were instructed to perform three cross punches directed to a fixed elastic target triggered by the coach whistling, and were monitored through a surface electromyography sensor (EMG) on the biceps brachii to estimate the muscular activation during the performance, and through an accelerometer placed inside the elastic impact target to estimate the impact energy. We analyzed the oscillatory content of the EMG signal in order to assess the muscular activation between skilled and unskilled boxers, and between weak and strong punches. Results: both skilled and unskilled boxers threw strong, medium and weak strikes. Skilled boxers performed better than unskilled boxers (47% vs 25% in the “strong punch” category).The EMG analysis revealed a significant increase of lower and higher frequencies (2-4 Hz and 15-17 Hz) and a decrease on the medium frequencies (7-9 Hz) in the skilled boxers compared to the unskilled boxers in strong punches. Weak punches had a similar activation patterns in the two groups. Conclusions: our results support the hypothesis that skilled boxers adapt their activation pattern of the biceps to better stabilize the punch delivery (and thus increasing the transfer of force).