Which muscle is primarily responsible for elbow extension?

• A. Biceps
• B. Triceps
• C. Deltoid
• D. Latissimus

Answer: (B)

Elbow extension is produced by the muscles on the back of the upper arm, with the triceps brachii as the primary mover. The triceps has three heads that all attach to the olecranon of the ulna; when it contracts, it pulls the ulna straight back, extending the elbow. This makes it the main elbow extensor.

The biceps brachii, in contrast, is the major elbow flexor and also helps with forearm supination, so its action is to bend the elbow rather than straighten it. The deltoid is a shoulder muscle focused on lifting and moving the arm at the shoulder joint, not assisting elbow extension. The latissimus dorsi is involved in shoulder movement and back extension, not directly extending the elbow.

So, the muscle chiefly responsible for elbow extension is the triceps brachii.