During elbow flexion MMT, which forearm position isolates the brachialis?

During elbow flexion MMT, which forearm position isolates the brachialis?

• A. Pronated
• B. Supinated
• C. Neutral
• D. Flexed and pronated

Answer: (A)

Placing the forearm in pronation biases elbow flexion to come mainly from the brachialis. The brachialis is the primary elbow flexor when the forearm is pronated because its line of pull on the ulna is favorable in that position, and it operates largely independent of the radius. In pronation, the biceps brachii loses much of its ability to contribute to elbow flexion (it’s more active with supination) and the brachioradialis’ contribution is reduced since it works best in neutral. With the biceps and brachioradialis minimized, the brachialis does most of the work, making it the best position to isolate it during elbow flexion MMT. Supination would recruit the biceps more, neutral would involve multiple muscles, and a flexed and pronated position isn’t typically used to isolate the brachialis.

Placing the forearm in pronation biases elbow flexion to come mainly from the brachialis. The brachialis is the primary elbow flexor when the forearm is pronated because its line of pull on the ulna is favorable in that position, and it operates largely independent of the radius. In pronation, the biceps brachii loses much of its ability to contribute to elbow flexion (it’s more active with supination) and the brachioradialis’ contribution is reduced since it works best in neutral. With the biceps and brachioradialis minimized, the brachialis does most of the work, making it the best position to isolate it during elbow flexion MMT. Supination would recruit the biceps more, neutral would involve multiple muscles, and a flexed and pronated position isn’t typically used to isolate the brachialis.