Which term describes muscle contractions where the load causes the muscle to shorten while maintaining constant tension?

• A. Isotonic contractions
• B. Isometric contractions
• C. Treppe
• D. Wave summation

Answer: (A)

Isotonic contractions describe a muscle shortening while a constant load is moved. In this type of contraction, the muscle generates enough force to overcome a fixed resistance and its length decreases as it contracts, producing movement such as lifting a weight. The tension the muscle produces remains about the same while the length changes, which is the hallmark of isotonic work. In contrast, isometric contractions produce force without any change in length, and treppe or wave summation refer to other phenomena related to how force changes with repeated stimuli, not to whether the muscle shortens under a constant load.