biceps

The movements of the arm depend on two muscles, the biceps and the triceps. To lift the arm, the biceps shortens and the triceps lengthens. To lower the arm, the opposite occurs: the biceps lengthens and the triceps shortens.

Anatomical term for two muscles of the human body, one of the arm and one of the leg, although in popular use it generally denotes the muscle of the arm. The biceps brachii is the muscle on the upper arm, which flexes the shoulder, the elbow, and supinates the forearm. To extend the arm its antagonistic muscle - the triceps - has to contract.

The biceps femoris extends along the whole of the back of the thigh and flexes the knee.

Each muscle has two heads or points of origin.