Peroneus longus can not be fully activated during ankle complex exercises by uninjured subjects

This study characterized, for the first time, the extent to which the peroneus longus muscle can be voluntarily activated by uninjured subjects during common ankle rehabilitative exercises. Ten healthy subjects performed isometric maximum voluntary contractions (MVCs) of eversion and plantarflexion on a dynamometer and against manual resistance, and performed dynamic whole-body activities that place large loads on the ankle complex (vertical jumps and side-cuts). During these activities, surface EMG signals were collected from the peroneus longus and expressed as a percentage of the maximum motor responses elicited by electric stimulation. Voluntary activation levels of the peroneus longus during isometric MVCs performed on the dynamometer and performed against manual resistance were not significantly different. Side-cuts produced significantly larger activation levels than those maximum vertical jumps and the isometric exercises. Nevertheless, the activation levels were substantially lower than those reported for other lower extremity muscles. These results serve as the basis for further questions related to whether voluntary peroneus longus activation level can be affected by specific rehabilitative efforts, whether activation levels are influenced by acute and chronic ankle complex injuries and, if so, whether this effect influences the functional outcome of rehabilitation efforts following ankle injuries.