The major muscles of the posterior shin are the gastrocnemius, which shapes the back surface of the shin, and the soleus. Collectively, these muscles are known as the calf muscles or the triceps surae group. The gastrocnemius has two distinct heads which lie side by side and can easily be seen if the muscle is well developed.

Origin

Both heads originate by separate tendons from the condyles of the femur (thigh bone).

Insertion

At the lower it combines with the soleus into the Achilles tendon, which attaches to the calcaneus (heel bone).

Function

Ankle joint extension (plantar flexion). At the knee joint the gastrocnemius is involved in knee joint flexion.

Heel Raise (Calf Raise)

Glute-Ham-Gastroc Raise