Which muscles plantarflex the ankle?

• A. Tibialis anterior
• B. Extensor digitorum longus
• C. Gastrocnemius and soleus
• D. Fibularis brevis

Answer: (C)

Plantarflexion is the movement of pointing the foot downward at the ankle, which is produced mainly by the muscles in the back of the lower leg that pull on the heel via the Achilles tendon. The primary performers are the gastrocnemius and the soleus, together forming the triceps surae. They attach to the calcaneus and generate the powerful push-off needed in standing and walking. The gastrocnemius crosses the knee, so it works best when the knee is extended, while the soleus works consistently since it does not cross the knee. The other options do not plantarflex the ankle as their main action: the tibialis anterior dorsiflexes the foot, the extensor digitorum longus also dorsiflexes and extends the toes, and the fibularis brevis mainly everts the foot with only a weaker plantarflexion.