Alterations in co-activation around the ankle joint after specific training, do not affect vertical jumping kinematics and performance.

Abstract

The aim of this study was to examine the effects of ankle-specific plyometric exercises and electromyostimulation (EMS) on vertical jump biomechanics. Thirty participants were divided into three training groups: a) incline plyometrics group, b) plane plyometrics group and c) EMS group. Each group followed a 4 weeks training period. The plyometric training session consisted of eighty vertical hops as fast as the participants could while EMS training included eighty fast contractions in 15° plantar flexion. Take-off velocity (Vto) and sagittal kinematics of the hip, the knee, and the ankle joints were recorded and analyzed. The kinetics data were also analyzed before and after the intervention. The muscle activity of the medial gastrocnemius (MGAS) and the co-activation index between the Tibialis Anterior (TA) and the MGAS was recorded and evaluated during CMJ before and after training. A non-significant effect of training on Vto, sagittal kinematics, and muscle activity was observed for the training groups after the training period. In contrast, all the intervention groups were found to increase ground reaction forces and rate of force development significantly during the CMJ. Co-activation index was increased after plane plyometrics and EMS training for CMJ in contrast to the incline hopping. The present results indicate that specific ankle training could result in alterations of the dynamic parameters as well as in muscle co-activation during the CMJ after a four-week intervention. These changes do not include increases in the kinematics or vertical performance. The present results suggest that a longer training period is needed to observe significant changes in vertical jumping technique and performance.