Which contraction shortens the muscle while producing force?

• A. Eccentric contractions
• B. Isometric contractions
• C. Isotonic contractions
• D. Concentric contractions

Answer: (D)

Concentric contraction occurs when a muscle shortens as it generates force to move a segment. This shortening drives the lifting phase of a movement, like curling a weight or rising from a squat, so it’s the best match for “shortens the muscle while producing force.”

An eccentric contraction, in contrast, lengthens the muscle while still producing force as you control the lowering of a load. An isometric contraction holds a position with no change in muscle length while producing force. Isotonic contractions describe movements with a constant load and include both shortening (concentric) and lengthening (eccentric) phases, but the specific shortening under load is the concentric type.