Certified Travel Counselor (CTC) Practice Exam

Which statement best describes an eccentric action in muscle contraction?

1. External force exceeds the contractile force generated by a muscle

2. Muscle shortens and overcomes the resistive force

3. External resistance matches the muscular tension

4. Movement is controlled by speed regardless of force

The correct answer is: External force exceeds the contractile force generated by a muscle

An eccentric action in muscle contraction occurs when a muscle lengthens while under tension, typically in response to an external force that exceeds the force generated by the muscle itself. This is often seen during activities such as lowering a weight or descending stairs, where the muscle must control the movement against gravity or another resistance. When an external force exceeds the contractile force of a muscle, the muscle cannot shorten and instead lengthens, which is characteristic of eccentric contractions. This is important for activities that require controlled movement and helps in decelerating body motion, protecting joints, and reducing the risk of injury. The other statements describe different muscle contraction scenarios: a shortening of the muscle where it overcomes resistive force denotes a concentric contraction, equal external resistance to muscular tension relates to isometric contraction, and controlling movement by speed regardless of force does not accurately capture the essence of eccentric actions. In essence, the primary defining feature of eccentric contraction is that the muscle is actively lengthening while resisting an external force that is greater than its own generated force.