Elbow flexion. Artwork of the muscles of the arm from the front, with red arrows showing the direction of movement when flexing (bending) the elbow. The flexion here is shown from the 90 degrees position towards the maximum of 145 degrees (red arrows at top). This maximum is reached as the muscles of the forearm and upper arm come into contact and harden, especially the biceps brachii (red arrows, bottom). The main muscles involved in elbow flexion are the brachialis of the elbow, the brachioradialis of the forearm, and the biceps brachii of the upper arm. The nerve used is the musculocutaneous nerve. This is the right arm. For the left arm, see C016/6790.