Muscle of the lower leg. Medial head: ORIGIN: Upper posterior medialcondyle and femur above this INSERTION: Through tendocalcaneus into mid posterior calcaneus ACTION: Flexes leg and plantar flexes foot .Lateral head: ORIGIN: Upper posterior lateralcondyle and femur above this INSERTION: Through tendocalcaneus into mid posterior calcaneus ACTION: Flexes leg and plantar flexes foot. http://www.graylab.ac.uk/cgi-bin/omd?gastrocnemius
The anterior compartment muscles (tibialis anterior, extensor hallucis longus, extensor digitorum longus) hold the forefoot up during foot descent and contract eccentrically once the heel strikes the ground. The much larger gastrocnemius and soleus muscles pull the forefoot down. The tremendous stress of eccentric contractions can damage the anterior compartment muscles.