There are three muscles that function on the back of the leg for plantar flexion: the gastrocnemius, the soleus and the plantaris. Plantar flexion involves moving the foot downward toward the ground.
Since performing plantar flexion sometimes involves supporting the entire body at the ankle joint as often done by ballerinas, the muscles used for plantar flexion are a lot bigger than the muscles used for dorsiflexion. The dorsiflexion motion is the simple lifting of the foot and utilizes one muscle on the front of the leg. The tibialis anterior muscle is used to perform the dorsiflexion motion at the ankle joint.