Which muscle contraction occurs with no change in muscle length?

The correct answer is isometric contraction because this type of muscle contraction occurs when the muscle generates tension without changing its length. During an isometric contraction, the muscle fibers are engaged, and although they are producing force, there is no movement at the joints involved. This is often seen when holding a weight in a fixed position, such as performing a wall sit or pushing against an immovable object.

In contrast, eccentric contraction involves the muscle lengthening while under tension, typically occurring when a muscle is actively resisting a force that is greater than the force it can produce. Concentric contraction is where the muscle shortens as it generates force, like during the upward phase of a bicep curl. Isotonic contraction refers to muscle contractions that result in movement, where the muscle changes length while maintaining constant tension. Understanding the differences between these types of contractions helps in designing effective workout programs and understanding muscular function during exercise.