Altered leg muscle activity in volleyball players with functional ankle instability during a sideward lateral cutting...

To study the activation patterns of tibialis anterior, peroneus longus and gastrocnemius lateralis muscles during a lateral shuffle maneuver in volleyball players with functional instability of the ankle joint.

Observational case-control study.

Research laboratory.

Sixteen players with functional instability and 18 matched controls.

RMS values of tibialis anterior, peroneus longus and gastrocnemius lateralis muscles for the 50 ms before initial ground contact, timing of onset of muscle activity and linear envelopes for the period of ground contact were calculated.

Onset values showed similar patterns of activation for both groups. In healthy subjects, gastrocnemius lateralis activated earlier, followed by peroneus longus and tibialis anterior. In the unstable subjects, gastrocnemius lateralis and peroneus longus activated at the same time, followed by tibialis anterior. Unstable subjects also presented lower peroneus longus activity during the 50 ms before initial ground impact, a lower peroneus longus peak magnitude and a higher gastrocnemius lateralis peak magnitude.

Volleyball players with ankle functional instability showed decreased peroneus longus activity before ground impact that may predispose them to repetitive sprains and explain their "giving way" sensation, since peroneus longus is the main ankle evertor and an important stabilizer against sudden and excessive inversion.