Antagonists are plantar-flexors of the posterior compartment such as soleus and gastrocnemius. Along with the soleus muscle, the gastrocnemius forms half of the calf muscle. Three muscles insert on the calcaneus&colon; the gastrocnemius, soleus, and plantaris. The triceps surae consists of the soleus and the two heads of the gastrocnemius. Deep to the gastrocnemius (farther from the skin) is the soleus muscle. The tibial nerve eventually separates from the sciatic nerve and innervates the gastrocnemius muscle. Change in running pace may cause Achilles Tendinitis, gastrocnemius injuries, and plantar fasciitis. The gastrocnemius muscle acts on both joints. The gastrocnemius muscle may also become inflamed due to overuse. This nerve courses laterally over the lateral head of the gastrocnemius. This was eventually diagnosed as a gastrocnemius tear in his left calf muscle. The gastrocnemius also flexes the leg at the knee. The lateral gastrocnemius is an example of this muscle architecture. The plantaris closely follows the lateral head of the gastrocnemius. The plantaris is considered an unimportant muscle and mainly acts with the gastrocnemius.