During elbow flexion, which muscle relaxes to allow the movement?

During elbow flexion, which muscle relaxes to allow the movement?

• A. Bicep
• B. Tricep
• C. Deltoid
• D. Brachioradialis

Answer: (B)

During elbow flexion, the movement is produced by the flexor muscles on the front of the arm pulling the forearm toward the upper arm. For this bend to happen smoothly, the muscle on the back of the arm—the antagonist—must relax so it isn’t pulling the elbow straight or resisting the bend. That relaxing muscle is the triceps brachii. If the triceps stayed tight, elbow flexion would be harder or limited because the opposing force would keep the joint extended. The biceps brachii is a primary mover for elbow flexion, so it contracts rather than relaxes. The brachioradialis also helps with elbow flexion in certain forearm positions, but it isn’t the muscle that must relax to permit the movement. The deltoid acts mainly at the shoulder and doesn’t control elbow flexion directly.

During elbow flexion, the movement is produced by the flexor muscles on the front of the arm pulling the forearm toward the upper arm. For this bend to happen smoothly, the muscle on the back of the arm—the antagonist—must relax so it isn’t pulling the elbow straight or resisting the bend. That relaxing muscle is the triceps brachii. If the triceps stayed tight, elbow flexion would be harder or limited because the opposing force would keep the joint extended.

The biceps brachii is a primary mover for elbow flexion, so it contracts rather than relaxes. The brachioradialis also helps with elbow flexion in certain forearm positions, but it isn’t the muscle that must relax to permit the movement. The deltoid acts mainly at the shoulder and doesn’t control elbow flexion directly.