Which muscle is the prime mover of elbow flexion in pronation/supination?

Which muscle is the prime mover of elbow flexion in pronation/supination?

• A. Brachioradialis
• B. Biceps brachii
• C. Brachialis
• D. Triceps brachii

Answer: (A)

The way the forearm is rotated changes which elbow flexor is most effective. The brachioradialis crosses the elbow and has a favorable line of pull when the forearm is rotated, so it provides the greatest elbow flexion torque in pronation or other rotated positions. The biceps brachii, while a strong elbow flexor, relies on a supinated forearm for maximal contribution and becomes less effective when the forearm is pronated. The brachialis is a powerful elbow flexor regardless of position, but in rotating forearms its role is usually overshadowed by the brachioradialis. The triceps brachii extends the elbow, not flex it. So, in pronation or rotated forearm positions, the brachioradialis acts as the prime mover for elbow flexion.

The way the forearm is rotated changes which elbow flexor is most effective. The brachioradialis crosses the elbow and has a favorable line of pull when the forearm is rotated, so it provides the greatest elbow flexion torque in pronation or other rotated positions. The biceps brachii, while a strong elbow flexor, relies on a supinated forearm for maximal contribution and becomes less effective when the forearm is pronated. The brachialis is a powerful elbow flexor regardless of position, but in rotating forearms its role is usually overshadowed by the brachioradialis. The triceps brachii extends the elbow, not flex it. So, in pronation or rotated forearm positions, the brachioradialis acts as the prime mover for elbow flexion.