Which statement best describes an example of isometric contraction?

Isometric contractions occur when a muscle is activated and generates force, but there is no movement at the joint. This means the muscle length remains constant despite the exertion of force. Holding a weight in a fixed position exemplifies this, as the muscles are contracted and tense to maintain that position without producing movement. This type of contraction is essential for stabilizing joints and maintaining posture.

In contrast, lifting a heavy weight with full muscle extension involves dynamic movements and changes in muscle length, distinguishing it from an isometric contraction. Stretching a muscle at its maximum length does not involve contraction in the traditional sense but rather elongation of the muscle fibers. Lifting a leg straight up without any resistance also reflects a dynamic movement, which shows muscle shortening rather than maintaining a steady contraction without movement. Each of these examples illustrates different types of muscle contractions, reinforcing the definition and significance of isometric contractions in exercise and strength training.