Which term describes the muscle that is being stretched?

Which term describes the muscle that is being stretched?

• A. Agonist
• B. Antagonist
• C. Open Chain
• D. Closed Chain

Answer: (B)

In a movement, the muscle that actively shortens to produce the action is the agonist, while the opposing muscle that lengthens to allow that motion is the antagonist. So the muscle being stretched is the antagonist. For example, during elbow flexion, the biceps brachii acts as the agonist, shortening to bring the hand toward the shoulder, and the triceps brachii lengthens as the antagonist to permit that bend. Note that open chain and closed chain describe how the limb moves relative to a fixed point, not which muscle is being stretched, so they don’t determine this role.

In a movement, the muscle that actively shortens to produce the action is the agonist, while the opposing muscle that lengthens to allow that motion is the antagonist. So the muscle being stretched is the antagonist.

For example, during elbow flexion, the biceps brachii acts as the agonist, shortening to bring the hand toward the shoulder, and the triceps brachii lengthens as the antagonist to permit that bend. Note that open chain and closed chain describe how the limb moves relative to a fixed point, not which muscle is being stretched, so they don’t determine this role.