In humans, the
gastrocnemius muscle ( or ; plural
gastrocnemii;
Latin, from
Greek γαστήρ "stomach" and
κνήμη (
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.