The name stands for Neuro-Muscular Electrical Stimulation and it is the same technology as is used in T.E.N.S. devices.
In the case of muscle stimulation, where you want to cause a muscle “twitch” or contraction on purpose, the output current is usually stronger and the “pulse width” is generally made wider or increased above where you would normally set it for T.E.N.S. (pain control).
Where the usual settings for conventional or high-frequency T.E.N.S. involve pulse rates in the 100-150 Hz (pulses per second) range, a rate of 30-50 Hz would be used for N.M.E.S. applications so as to not prematurely fatigue the target muscles. As most rehabilitation protocols call for lots of “reps” (repetitions) it is important to be able to do a muscle stim treatment for 15 – 30 minutes. The higher the frequency the more rapid the tiring of the muscle tissues, so this time period may not be possible unless the parameters are adjusted properly.
Another factor to be considered in any N.M.E.S. treatment regimen is the “duty cycle” of the stimulation. This would be the length of time the muscle is actually contracted compared to the time it “rests” between contractions. Usual treatments are in the range of 5-15 seconds “ON” with an “OFF” time of 10-30 seconds.
If the approach is to gain endurance in the muscle then it is more important to have increased “OFF” times (ie. less fatigue) in order to be able to do the maximum number of repetitions in the time allotted.
If, however, the goal is to achieve a major increase in bulk or strength, then a more aggressive approach using longer “ON” times and shorter “OFF” times is required. The fatiguing of muscles will be more evident and may require less frequent sessions.
Another thing to note is that some N.M.E.S. units also have T.E.N.S. capability. In other words you would be able to use the same device to rehabilitate your atrophied muscle and also use it for pain control as required.