Central common drive to antagonistic ankle muscles in relation to short-term co-contraction training in non-dancers and professional ballet dancers

Optimization of co-contraction of antagonistic muscles around the ankle joint has been shown to involve plastic changes in spinal and cortical neural circuitries. Such changes may explain the ability of elite ballet dancers to maintain a steady balance during various ballet postures. Here we investigated whether short-term co-contraction training in ballet dancers and non-dancers leads to changes in the coupling between antagonistic ankle motor units. Eleven ballet dancers and ten non-dancers were recruited for the study. Prior to training, ballet dancers and non-dancers showed an equal amount of coherence in the 15-35 Hz frequency band and short-term synchronization between antagonistic tibialis anterior and soleus motor units. The ballet dancers tended to be better at maintaining a stable co-contraction of the antagonistic muscles, but this difference was not significant (P = 0.09). Following 27 minutes of co-contraction training the non-dancers improved their performance significantly, whereas no significant improvement was observed for the ballet dancers. The non-dancers showed a significant increase in 15-35 Hz coherence following the training, whereas the ballet dancers did not show a significant change. A group of control subjects (n = 4), who performed co-contraction of the antagonistic muscles for an equal amount of time, but without any requirement to improve their performance, showed no change in coherence. We suggest that improved ability to maintain a stable co-contraction around the ankle joint is accompanied by short-term plastic changes in the neural drive to the involved muscles, but that such changes are not necessary for maintained high-level performance.