Which waveform category is NOT typically used for NMES?

• A. Monophasic (HVPC)
• B. Biphasic asymmetrical
• C. Biphasic symmetrical
• D. Polyphasic

Answer: (A)

NMES relies on charge-balanced, bidirectional waveforms to produce controlled muscle contractions safely. Monophasic (HVPC) is not typically used because it delivers a net direct current with a single polarity. This can cause electrode polarization, skin irritation or burns, and less comfortable stimulation when used repeatedly. In contrast, biphasic symmetrical, biphasic asymmetrical, and polyphasic waveforms balance the charge per pulse, minimize polarization, and allow comfortable, effective motor unit recruitment. Those charge-balanced options are standard for NMES, which is why monophasic HVPC is the not-typical choice.