In the activity of lowering a five-pound bag from the top shelf to the countertop, what would the biceps brachii be performing?

• A. Concentric contraction
• B. Isometric contraction
• C. Eccentric contraction
• D. Cocontraction

Answer: (C)

Controlling a lowering movement relies on eccentric contraction, where a muscle lengthens while producing tension to slow the motion. As you lower the bag, gravity tends to pull the forearm downward, and the biceps brachii must resist that pull to keep the descent smooth. It lengthens while still actively controlling the movement, which is exactly an eccentric contraction. If you were lifting the bag, the biceps would shorten (concentric). If you held the position with no movement, that would be isometric. Cocontraction would involve the biceps and its antagonist (the triceps) contracting together to stabilize, which isn’t the primary action during a controlled lowering.