Which statement accurately describes NMES motor responses?

• A. Direct motor response via peripheral pathways and reflex motor response via spinal reflexes
• B. Voluntary motor response and reflex motor response
• C. Cortical motor response and brainstem response
• D. Autonomic response and somatic response

Answer: (A)

Two distinct NMES motor responses occur: a direct motor response and a reflex motor response. The direct motor response happens when the electrical pulse directly depolarizes motor fibers in peripheral nerves or the muscle’s own endplates, causing a contraction without engaging spinal reflex circuits. The reflex motor response arises when the stimulus excites sensory afferent fibers that enter the spinal cord and trigger a reflex pathway, adding a contraction mediated by the spinal circuitry. These two pathways explain why NMES can produce robust contractions even at lower stimulation levels: some recruitment is direct, and some comes from reflex-driven activation.

Other descriptions aren’t how NMES primarily works: voluntary motor responses require conscious cortical drive, which NMES does not depend on; a cortical motor or brainstem response would imply central activation patterns not specific to NMES; autonomic responses involve involuntary control of organs rather than skeletal muscle contraction.