The plantaris is one of the superficial muscles of the superficial posterior compartment of the leg, one of the fascial compartments of the leg.
In humans, the gastrocnemius muscle (Latin, from Greek "stomach" and (knēmē) "leg"; meaning "stomach of leg" referring to the bulging shape of the calf) is a very powerful superficial bipennate muscle that is in the back part of the lower leg. It runs from its two heads just above the knee to the heel, a two joint muscle.
In humans and some other mammals, the soleus is a powerful muscle in the back part of the lower leg (the calf). It runs from just below the knee to the heel, and is involved in standing and walking. It is closely connected to the gastrocnemius muscle and some anatomists consider them to be a single muscle, the triceps surae. Its name is derived from the Latin word "solea", meaning "sandal".