The brachialis muscle is one of the major skeletal muscles of the upper arm (brachial region). It is the strongest flexor of the arm at the elbow, working alongside the biceps brachii and brachioradialis. The brachialis is a deep muscle of the arm, so while it’s very important and powerful, it’s much less visible and less widely known than the biceps brachii, another flexor of the elbow.
The brachialis muscle is a large, powerful muscle of the upper arm. It arises from wide origins on the anterior surface of the humerus between the epicondyles and tapers to a point medial to the deltoid tuberosity. From its origins, the brachialis muscle descends along the arm, crossing the anterior side of the elbow joint. The muscular belly has a flat, diamond shape, with narrow tapered points near the origin and insertion and a much wider region in between. In the forearm, the brachialis inserts on the coronoid process of the ulna. The brachialis is a deep arm muscle, lying close to the bones and elbow joint and underneath the biceps brachii muscle.
Contraction of the brachialis draws its insertion on the ulna closer to its origin on the anterior humerus, flexing the elbow joint. It is the main feature that flexes the elbow joint, exerting more force than both the biceps brachii and the brachioradialis. It also only performs one motion compared to the brachioradialis and biceps brachii, which are involved in pronation and supination of the forearm.