Which contraction occurs when the joint angle changes with the muscle shortening, such as curling a weight toward you?

Which contraction occurs when the joint angle changes with the muscle shortening, such as curling a weight toward you?

• A. Isometric
• B. Eccentric
• C. Concentric
• D. Plyometric

Answer: (C)

When a muscle shortens while the joint moves, that action is a concentric contraction. Curling a weight toward you makes the biceps shorten as they pull the forearm up, which decreases the elbow angle. That shortening with movement is the defining feature of a concentric contraction. If the elbow angle stayed the same while the muscle tensed, that would be isometric. If the muscle were lengthening while generating force—like lowering the weight slowly—the motion would be eccentric. Plyometric describes a training method involving rapid stretch and shortening, not a single contraction type, so it isn’t the correct label for this lifting action.

When a muscle shortens while the joint moves, that action is a concentric contraction. Curling a weight toward you makes the biceps shorten as they pull the forearm up, which decreases the elbow angle. That shortening with movement is the defining feature of a concentric contraction. If the elbow angle stayed the same while the muscle tensed, that would be isometric. If the muscle were lengthening while generating force—like lowering the weight slowly—the motion would be eccentric. Plyometric describes a training method involving rapid stretch and shortening, not a single contraction type, so it isn’t the correct label for this lifting action.