In Plain English
The brachialis is a muscle that sits directly beneath the biceps at the front of the upper arm. Although it’s mostly hidden, it generates a large portion of your elbow bending strength. As it grows, it pushes the biceps outward, making the entire upper arm appear thicker.
Technical Definition
The brachialis is a deep muscle of the anterior upper arm, originating from the distal anterior surface of the humerus and inserting onto the ulnar tuberosity and coronoid process of the ulna. Its primary function is elbow flexion, and because it inserts onto the ulna rather than the radius, it produces elbow flexion regardless of whether the forearm is pronated, neutral, or supinated. This makes it one of the strongest and most consistent elbow flexors in the body.
















