, your biceps muscle is attached to your shoulder blade at one end and to your ulna in your forearm at the other end. When the biceps contracts, it shortens and pulls the ulna toward the shoulder blade (the ulna is attached to the elbow joint). This movement allows you to lift your forearm and a given load.
Full Answer
Different muscle groups are responsible for the action of the major joints in the leg. For example the muscles of the buttocks, hips