Coupling between punch efficacy and body stability for elite karate

Summary 

In order to be successful in karate, it is necessary to apply the highest punch impulse at impact while maintaining dynamic body stability during the entire action. Here we test two different techniques to execute a specific karate punch and we compare expert and novice performances to explore the punch efficacy at different skill levels. Each participant, standing on a force platform, was asked to punch a 25kg box as hard as possible. The Centre of Pressure (CoP) migration and the kinematics of the upper limb were analysed. Experts (compared to novices) showed, as expected, higher upper limb velocity, punch impulse and a larger box displacement. Interestingly, while the CoP area considered both during and after the punch was the same for both groups, the amount of backward CoP displacement per unit of impulse applied was significantly lower for experts compared to novices. Collectively these results show the specific strategy used to maintain body stability in karate experts.

Keywords: Centre of pressure, Principal component analysis, Postural stability, Impact force