What type of muscle contraction occurs without a change in muscle length?

An isometric contraction is characterized by the muscle generating force without any change in length. During isometric contractions, the muscle fibers maintain a constant length while still producing tension. This type of contraction often occurs when a muscle exerts force against an immovable object, such as pushing against a wall, or when the body is stabilizing a position, like holding a plank.

In contrast, isotonic contractions involve a change in muscle length, whether it is a concentric contraction (muscle shortening) or an eccentric contraction (muscle lengthening). Isokinetic contractions also involve muscle length changes but are defined by the speed of movement being kept constant throughout the range of motion, typically requiring specialized equipment. Therefore, isometric contractions are unique in maintaining muscle length while generating force, making them the correct answer to this question.