Which type of contraction involves a muscle tensing without changing length?

The type of contraction that involves a muscle tensing without changing length is known as an isometric contraction. During an isometric contraction, the muscle generates tension but does not shorten or lengthen; it maintains a static position. This type of contraction is often involved in activities where a joint angle remains constant despite the application of force, such as holding a weight in a fixed position or pushing against an immovable object.

In contrast, eccentric contractions occur when a muscle elongates while under tension, usually as it controls the speed of a movement such as lowering a weight. Isotonic contractions consist of muscle shortening (concentric) or lengthening (eccentric) while the tension remains constant. Concentric contractions involve the muscle shortening as it generates force, typically during the lifting phase of a movement. Understanding these distinctions helps clarify muscle function during different types of physical activities.