The medial head of gastrocnemius does what action?

• A. Plantarflexion
• B. Dorsiflexion
• C. Inversion
• D. Eversion

Answer: (A)

Plantarflexion of the foot at the ankle is the action in question. The medial head of the gastrocnemius is one of the two heads of the gastrocnemius in the posterior leg and it inserts into the calcaneus via the Achilles tendon. When it contracts, it pulls the heel upward and the toes downward, producing plantarflexion at the ankle. It also crosses the knee, so it can assist knee flexion, but the movement being asked about is at the ankle. Dorsiflexion is the opposite movement and is performed by anterior compartment muscles; inversion and eversion occur at the subtalar joint and involve different muscles (inversion mainly by tibialis posterior, eversion by peroneal muscles). So plantarflexion is the correct action.