Which term describes a muscle contraction where the muscle lengthens?

The term that describes a muscle contraction where the muscle lengthens is eccentric. In an eccentric contraction, the muscle exerts force while being elongated, often while controlling or decelerating a movement. This type of contraction commonly occurs during activities such as lowering weights or running downhill, where the muscle is working to manage the load or the speed at which the body is moving.

Understanding the significance of eccentric contractions is important because they play a crucial role in muscle strengthening, injury rehabilitation, and overall functional movement. They are also known to produce more muscle damage than concentric contractions, which can lead to greater muscle growth during recovery.

The other terms refer to different types of muscle contractions: concentric contractions involve shortening of the muscle, isometric contractions mean the muscle length does not change while exerting force, and elastic typically refers to the stretching and returning of muscle or tissue but is not a specific type of muscle contraction.