Which term describes a muscle that is shortening against a resistance?

The term that describes a muscle shortening against a resistance is known as concentric muscle action. This occurs when a muscle generates force while its length decreases, allowing it to overcome the resistance being applied. For example, when performing a bicep curl, as you lift the weight upwards, the bicep muscle contracts and shortens, demonstrating concentric contraction.

Isometric muscle action refers to a situation where the muscle is generating force without changing its length, meaning there is no movement of the joint or shortening of the muscle. Eccentric muscle action, on the other hand, involves the muscle lengthening under tension, which typically happens when a muscle slows down a movement or controls the descent of a weight, such as lowering the bicep curl back down. These distinctions are crucial in understanding how muscles function during different types of movement, emphasizing the importance of concentric action in lifting and performing tasks that require force production against a resistance.