Which statement best describes NMES for denervated versus innervated muscle in terms of current and pulse duration?

• A. Denervated muscle requires direct current with long pulse durations; innervated NMES uses short-pulse biphasic currents.
• B. Denervated uses short-pulse; innervated uses direct current long pulses.
• C. Both use alternating current with identical pulse durations.
• D. Denervated uses high-frequency alternating current; innervated uses direct current.

Answer: (B)

When a muscle is denervated, you can’t rely on the nerve to carry the stimulus to the muscle. To evoke a contraction, the stimulation must directly excite the muscle fibers themselves, which requires longer pulse durations (often in the milliseconds range) and is typically delivered with direct current or monophasic pulses. If the nerve is intact (innervated muscle), it's more efficient to use short-duration pulses, usually a biphasic or symmetrical pulsed current, to depolarize the motor nerve and recruit motor units.

So the best description is that denervated muscle needs direct current with long pulse durations, while innervated NMES uses short-pulse biphasic currents. This aligns with the physiology of direct muscle fiber stimulation versus nerve-mediated stimulation.