What is the primary action of the brachialis?

What is the primary action of the brachialis?

• A. Extends forearm
• B. Supinates forearm
• C. Flexes forearm
• D. Pronates forearm

Answer: (C)

Elbow flexion is the action produced by the brachialis. This muscle sits on the front of the upper arm and attaches from the humerus to the ulna (coronoid process and tuberosity). When it contracts, it pulls the ulna toward the humerus, bending the elbow. It acts as the main elbow flexor in all forearm positions, unlike the biceps, which also supinates the forearm and is less effective when the forearm is pronated. The brachialis does not extend the forearm, nor does it rotate the radius—those roles belong to the triceps (extension) and the pronators/supinator, respectively.

Elbow flexion is the action produced by the brachialis. This muscle sits on the front of the upper arm and attaches from the humerus to the ulna (coronoid process and tuberosity). When it contracts, it pulls the ulna toward the humerus, bending the elbow. It acts as the main elbow flexor in all forearm positions, unlike the biceps, which also supinates the forearm and is less effective when the forearm is pronated. The brachialis does not extend the forearm, nor does it rotate the radius—those roles belong to the triceps (extension) and the pronators/supinator, respectively.