The muscle opposite the agonist, which lengthens when the agonist contracts to move a limb, is called the what?

The muscle opposite the agonist, which lengthens when the agonist contracts to move a limb, is called the what?

• A. Agonist
• B. Antagonist
• C. Synergist
• D. Stabilizer

Answer: (B)

When one muscle contracts to produce a joint movement, the opposing muscle lengthens to allow that movement and help control it. That opposing muscle is the antagonist. It works in opposition to the agonist, providing braking action and stability so the motion is smooth rather than abrupt. For example, during elbow flexion, the biceps brachii acts as the agonist, shortening to bend the elbow, while the triceps brachii lengthens to accommodate that bend and resist the motion to keep it controlled. The other roles—synergists helping the agonist or stabilizers fixing a segment—don’t describe the opposing, lengthening muscle.

When one muscle contracts to produce a joint movement, the opposing muscle lengthens to allow that movement and help control it. That opposing muscle is the antagonist. It works in opposition to the agonist, providing braking action and stability so the motion is smooth rather than abrupt. For example, during elbow flexion, the biceps brachii acts as the agonist, shortening to bend the elbow, while the triceps brachii lengthens to accommodate that bend and resist the motion to keep it controlled. The other roles—synergists helping the agonist or stabilizers fixing a segment—don’t describe the opposing, lengthening muscle.