Final answer:
The statement is false; the heavier the load during an isotonic contraction, the slower the velocity of contraction due to the extra resistance that the muscle must overcome to move the load.
Step-by-step explanation:
False. During isotonic contraction, muscle length changes to move a load, but the velocity of contraction doesn't increase with a heavier load. It's actually the opposite; as the load becomes heavier, the velocity of contraction decreases.
In isotonic contractions, the tension in the muscle stays relatively constant as the muscle changes length. There are two subtypes: concentric and eccentric. Concentric contractions involve the muscle shortening under tension to lift a load. Another is the eccentric contraction, where the muscle lengthens under tension usually when lowering the load.
The ability of a muscle to contract and generate force decreases as the load exceeds the muscle's capacity. When this happens, the somatic nervous system adjusts the speed of muscle contraction. Heavy loads require more muscle tension, leading to a slower contraction speed than lighter loads because of the additional resistance that must be overcome.