True or false: Volitional motor unit recruitment is more fatiguing due to synchronous recruitment.

True or false: Volitional motor unit recruitment is more fatiguing due to synchronous recruitment.

• A. True
• B. False
• C. Not enough information
• D. Both are equally fatiguing

Answer: (B)

Volitional motor unit recruitment is typically less fatiguing because it uses asynchronous firing and the size principle. When you move voluntarily, motor units are recruited from smallest to largest and do so with varying timing, so not all units are active at once. This distributes the workload over many fibers and allows some units to rest while others work, which slows the buildup of fatigue. The statement implies fatigue comes from synchronous recruitment, which is more characteristic of electrical stimulation. NMES tends to activate many motor units simultaneously, including fast-fatigue-prone fibers, leading to quicker fatigue. So the claim that voluntary recruitment is more fatiguing due to synchronous recruitment is not correct.

Volitional motor unit recruitment is typically less fatiguing because it uses asynchronous firing and the size principle. When you move voluntarily, motor units are recruited from smallest to largest and do so with varying timing, so not all units are active at once. This distributes the workload over many fibers and allows some units to rest while others work, which slows the buildup of fatigue. The statement implies fatigue comes from synchronous recruitment, which is more characteristic of electrical stimulation. NMES tends to activate many motor units simultaneously, including fast-fatigue-prone fibers, leading to quicker fatigue. So the claim that voluntary recruitment is more fatiguing due to synchronous recruitment is not correct.