Which statement best defines an isometric exercise?

• A. The muscle length changes through a range of motion.
• B. The joint angle changes constantly during contraction.
• C. The muscle generates force but no joint movement.
• D. The muscle generates force with concentric shortening.

Answer: (C)

Isometric contraction involves generating force without changing the length of the muscle or the angle of the joint. In isometric exercise, you tense the muscle and hold a position against an immovable resistance, so there’s no movement of the joint even though the muscle is working hard. That static, hold-and-stabilize effort is what defines an isometric action.

For example, holding a plank or pushing against a wall without moving it uses an isometric contraction—the muscles are firing, but the joint angles stay constant.

The other ideas describe dynamic movements: changing muscle length through motion, joints moving during the effort, or the muscle shortening under load (concentric shortening). Those are not isometric contractions.