For NMES aimed at spasticity with maximal agonist contraction, what is the target frequency?

For NMES aimed at spasticity with maximal agonist contraction, what is the target frequency?

• A. 20-50
• B. 50-80
• C. 100-120
• D. 60-100

Answer: (C)

To get a strong, smooth contraction of the agonist muscle with NMES, you want a fused, tetanic contraction. That requires a high stimulation frequency, because as the pulse rate increases, the individual muscle fiber responses sum in time until they merge into one continuous contraction. This fused tetanus produces the greatest force output from the stimulated muscle, which is why, when aiming for maximal agonist contraction to counter spasticity, a high end of the typical NMES frequency range is used. Keep in mind that higher frequencies fatigue the muscle more quickly, so the contractions are best delivered in short bursts with appropriate rest, and the amplitude is adjusted to achieve the desired joint movement without overfatigue or discomfort. Lower frequencies produce only twitches or incomplete tetanus, which won’t maximize contraction.

To get a strong, smooth contraction of the agonist muscle with NMES, you want a fused, tetanic contraction. That requires a high stimulation frequency, because as the pulse rate increases, the individual muscle fiber responses sum in time until they merge into one continuous contraction. This fused tetanus produces the greatest force output from the stimulated muscle, which is why, when aiming for maximal agonist contraction to counter spasticity, a high end of the typical NMES frequency range is used.

Keep in mind that higher frequencies fatigue the muscle more quickly, so the contractions are best delivered in short bursts with appropriate rest, and the amplitude is adjusted to achieve the desired joint movement without overfatigue or discomfort. Lower frequencies produce only twitches or incomplete tetanus, which won’t maximize contraction.