Which term refers to the muscle contraction that causes movement?

Which term refers to the muscle contraction that causes movement?

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

Answer: (A)

The main concept is identifying the muscle that actively causes the joint motion. The term is agonist, the prime mover that contracts to produce movement. For example, during elbow flexion the biceps brachii shortens to bring the forearm toward the upper arm, acting as the agonist. The opposing muscle group, the antagonist, lengthens and helps control the motion to keep it smooth. Terms like open chain and closed chain describe how the movement occurs (whether the end of the limb is free or fixed) rather than which muscle is driving the action, so they don’t define the muscle causing the movement.

The main concept is identifying the muscle that actively causes the joint motion. The term is agonist, the prime mover that contracts to produce movement. For example, during elbow flexion the biceps brachii shortens to bring the forearm toward the upper arm, acting as the agonist. The opposing muscle group, the antagonist, lengthens and helps control the motion to keep it smooth. Terms like open chain and closed chain describe how the movement occurs (whether the end of the limb is free or fixed) rather than which muscle is driving the action, so they don’t define the muscle causing the movement.