What is the primary action of the triceps brachii?

What is the primary action of the triceps brachii?

• A. Flexes forearm
• B. Pronates forearm
• C. Extends forearm
• D. Adducts arm

Answer: (C)

The main function of the triceps brachii is to extend the forearm at the elbow. It attaches to the olecranon of the ulna, and when it contracts, it straightens the elbow by pulling the forearm posteriorly, opposite to elbow flexion. The long head can assist with shoulder movements (extension and some adduction), but the dominant action at the elbow is extension. The other options correspond to actions produced by different muscles: flexion of the forearm mainly by the biceps brachii and brachialis, pronation by pronator muscles, and arm adduction by shoulder girdle muscles like pectoralis major and latissimus dorsi.

The main function of the triceps brachii is to extend the forearm at the elbow. It attaches to the olecranon of the ulna, and when it contracts, it straightens the elbow by pulling the forearm posteriorly, opposite to elbow flexion. The long head can assist with shoulder movements (extension and some adduction), but the dominant action at the elbow is extension. The other options correspond to actions produced by different muscles: flexion of the forearm mainly by the biceps brachii and brachialis, pronation by pronator muscles, and arm adduction by shoulder girdle muscles like pectoralis major and latissimus dorsi.