International Sports Sciences Association (ISSA) Trainer Practice Exam

How is an isometric contraction defined?

1. A muscle shortens as it contracts

2. A muscle lengthens as it contracts

3. A muscle does not change length as it contracts

4. A muscle relaxes completely

The correct answer is: A muscle does not change length as it contracts

An isometric contraction is defined as a type of muscle contraction in which the muscle generates tension without changing its length. During this type of contraction, the muscle fibers contract and produce force, but because the external load is equal to the force generated by the muscle, there is no movement or change in muscle length. This form of contraction is commonly seen in situations where a person is holding a position or resisting a force, such as holding a weight stationary in a fixed position or pressing against an immovable object. Isometric contractions can help build strength, stabilize joints, and improve muscular endurance without the risk of injury associated with movements that require lengthening or shortening of the muscle. While the other options describe different forms of muscle contraction—concentric contraction where the muscle shortens and eccentric contraction where the muscle lengthens—the defining characteristic of an isometric contraction is the stability and maintenance of muscle length under tension.