Which muscle is the primary flexor of the forearm (arm at the elbow joint) during elbow flexion?

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

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the action of elbow flexion, which involves decreasing the angle between the forearm and the arm at the elbow joint.
2. Step 2: Identify the muscles involved in elbow flexion. The main muscles to consider are the biceps brachii, brachialis, and brachioradialis.
3. Step 3: Analyze the primary function of each muscle: the brachialis lies deep to the biceps brachii and attaches to the ulna, making it the strongest flexor of the forearm regardless of forearm position.
4. Step 4: Recognize that the brachioradialis assists in flexion but is more active when the forearm is in a mid-pronated position, and the triceps brachii is an extensor, not a flexor.
5. Step 5: Conclude that the brachialis is the primary flexor of the forearm at the elbow joint during elbow flexion due to its anatomical position and function.