The Brachialis muscle is the most powerful flexor in the arm, not the biceps as most people believe. Comprising most of the cubital fossa’s base, Brachialis is a muscle of the upper arm that starts on the frontal surface of the humerus’ distal half, very close to the deltoid’s point of insertion. From there, it drops down to the humerus at the elbow joint, massing together in a thick tendon terminating along two distinct points of the ulna.
Brachialis Anticus (Brachialis for short) is the prime generator of elbow flexion, providing as much as 50% more power that the biceps brachii muscle. So, contrary to popular opinion, enormous biceps do not necessarily evidence true arm strength. Control of the brachalis muscle comes from the musculocutaneous nerve and in most cases, radial nerve (C5-T1).