In which motion does a muscle lengthen while under tension?

The correct answer is eccentric motion, which occurs when a muscle lengthens while it is under tension. This typically happens during movements where the muscle contracts while being elongated, such as when lowering a weight or controlling the descent during a squat. In this scenario, the muscle is still actively engaged, generating force, but it is not shortening as it would in a concentric contraction.

Eccentric contractions are important for activities that involve deceleration and controlling movements against gravity. They play a crucial role in muscle strength and injury prevention. Understanding eccentric motion helps trainers develop effective strength training programs that leverage the benefits of this type of contraction.

In contrast, concentric motion involves a muscle shortening while generating tension, which typically occurs during lifting actions. Static motion refers to maintaining a position without changing the length of the muscle, such as holding a weight in a fixed position. Dynamic motion encompasses both concentric and eccentric contractions, but it does not specify the lengthening aspect associated with eccentric contraction. Thus, the clarity of defining muscle lengthening under tension is what makes eccentric the correct choice.