Which of the following muscles acts as the prime mover for flexing the forearm at the elbow?

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

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the concept of a 'prime mover' in muscle actions. A prime mover, also known as an agonist, is the muscle primarily responsible for producing a specific movement.
2. Step 2: Identify the movement described in the problem. Flexing the forearm at the elbow involves decreasing the angle between the forearm and the upper arm.
3. Step 3: Review the anatomy of the muscles listed in the options. The biceps brachii is a two-headed muscle located in the upper arm, and its primary function is flexion of the forearm at the elbow. The brachioradialis assists in flexion but is not the prime mover. The deltoid is responsible for arm abduction, and the triceps brachii is responsible for extension of the forearm at the elbow.
4. Step 4: Match the muscle's function to the movement described. Since the biceps brachii is the primary muscle responsible for flexing the forearm at the elbow, it is the correct answer.
5. Step 5: Confirm your understanding by visualizing or referencing diagrams of the muscles involved in elbow flexion to reinforce the concept of the biceps brachii as the prime mover.