Massage & Bodywork Licensing Practice Examination (MBLEx)

The correct choice is Extensor digitorum longus, which acts as a synergist with peroneus longus during foot eversion. Synergist muscles assist or work alongside a primary mover in performing a particular movement. In the case of foot eversion, peroneus longus is a key muscle responsible for this action, and the extensor digitorum longus contributes by aiding in the stabilization and motion of the foot.

Extensor digitorum longus primarily extends the toes and aids in foot eversion by helping to lift the foot and turn it outward. This action complements the work done by peroneus longus, enhancing overall efficiency and balance during movements that require foot eversion.

Other muscles listed, such as tibialis anterior and tibialis posterior, perform different functions, with tibialis anterior primarily involved in dorsiflexion and tibialis posterior playing a more significant role in foot inversion and plantarflexion. Extensor hallucis longus focuses on extending the big toe and has less involvement in the eversion process itself, making it less effective as a synergist to peroneus longus.