Which muscle is associated with elbow flexion and shoulder flexion while assisting in supination?

• A. Biceps Brachii
• B. Triceps Brachii
• C. Brachialis
• D. Deltoid

Answer: (A)

A muscle that crosses both the shoulder and elbow joints can influence both elbow and shoulder movements, and it can also affect forearm rotation. The biceps brachii fits this pattern: it has two heads that start on the scapula and insert on the radius, so it can flex the elbow and contribute to shoulder flexion. When the elbow is flexed, the biceps is also a powerful supinator of the forearm, turning the palm upward as the radius rotates. The brachialis, while a strong elbow flexor, lies entirely at the elbow and does not cross the shoulder or assist with supination. The deltoid also crosses the shoulder and can contribute to shoulder flexion, but it does not flex the elbow or assist in forearm rotation. The triceps extends the elbow rather than flexing it and does not aid in supination. Therefore, the muscle that best matches elbow flexion, shoulder flexion, and assisting in supination is the biceps brachii.