Which statement correctly describes isometric exercise?

• A. Muscle contraction with resistance
• B. Muscle contraction without shortening
• C. Muscle shortening and active movement
• D. No movement

Answer: (B)

Isometric exercise is a static contraction: the muscle develops force but does not change length. In these moves you tense the muscle and hold a position against resistance, so the joint doesn’t move and the muscle length stays the same. Think of a plank, a wall push against an immovable surface, or holding a squat position without letting the knee bend further. The key idea to recall is force generation without shortening the muscle.

The other descriptions miss that precise point. Contraction with resistance can describe many types of exercise, including dynamic ones where the muscle shortens. Shortening with movement is what happens in dynamic (isotonic) contractions, where the muscle length changes as you move. Saying there’s no movement is true for isometric in terms of joints, but it’s less specific about what the muscle is doing during the hold—namely, it’s generating force without changing length, which is the defining feature of isometric work.