The calf
The two heads of the gastrocnemius start on the femur just above the knee and form the bulge of the calf. The flat, broad soleus lies beneath it and starts on the tibia and fibula. The model shows it on the right leg, with the gastrocnemius removed. Together the two are called the triceps surae.
Muscles of the back of the leg, with the two heads of the gastrocnemius cut to show the soleus, and the tendo calcaneus on the heel bone, Gray's Anatomy, 1918, figure 438Wikimedia Commons, Henry Vandyke Carter, Public domain (Gray438.png)
Both end in the Achilles tendon on the back of the heel bone, the thickest and strongest tendon in the body. They raise the heel, push the body forward in walking and running and lift it on tiptoe. In running the tendon carries forces of up to about 12 times body weight.
The soleus works for most of the day, keeping the body from tipping forward over the ankles when standing. Its contractions also squeeze the deep veins of the leg and help push blood back toward the heart. The tendon is named after Achilles, the Greek hero who could be wounded only in his heel.
Sources
- Susan Standring (ed.), Gray's Anatomy, 42nd ed. (2020), chapters on the leg and on the ankle and foot.
- Paavo Komi, Relevance of in vivo force measurements to human biomechanics, Journal of Biomechanics 23, suppl. 1 (1990): 23-34.
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