What type of muscle contraction occurs when the muscle lengthens while under tension?

The correct answer is based on the nature of how muscles function during different types of contractions. An eccentric contraction occurs when a muscle lengthens while it is still under tension. This type of contraction typically happens during activities where the muscle is actively resisting a force that is greater than the force being generated by the muscle itself, such as when lowering a weight in a controlled manner.

During an eccentric contraction, although the muscle is generating tension, it is yielding to an external load, which can lead to muscle elongation. This process is essential for various movements and plays a significant role in activities such as walking down stairs, lowering weights, or any situation where controlled lengthening of the muscle is necessary to prevent injury and maintain stability.

In contrast, concentric contractions involve the muscle shortening while generating force, isometric contractions involve muscle tension with no change in length, and static movements generally refer to positions maintained without movement or change in muscle length. Thus, understanding the nuances of these contractions helps clarify why eccentric is the correct identification in this case.