In reciprocal inhibition NMES, which frequency range is used?

• A. 20-50
• B. 50-100
• C. 100-120
• D. 5-15

Answer: (A)

Reciprocal inhibition NMES relies on getting a smooth, sustained contraction of the antagonist muscle so that reflex pathways can inhibit the agonist. To achieve that reliably, the antagonist needs a frequency that reliably fuses into a tetanic contraction without causing excessive discomfort or fatigue. Frequencies in the 20-50 Hz range provide a strong, continuous contraction, which efficiently drives the inhibitory signals to the agonist. If the frequency is too low (5–15 Hz), you’d get individual twitches rather than a steady contraction, making the inhibition inconsistent. If it’s much higher (50–100 Hz or more), you get a very high-frequency, fused contraction that tends to increase discomfort and fatigue without additional benefit for this purpose. Therefore, 20–50 Hz is the most appropriate range.