You should feel a mild to moderately strong tingling or buzzing sensation. Some people experience a more unpleasant sensation described as burning or prickling; continued use of the TENS in this case may not be appropriate, however this sensation may dull and become comfortable.
Depending on the intensity and duration of your pain, you may or may not get immediate results. It can take several days or even several weeks to get the desired results. Differences in results may occur based on properties of skin resistance, type of pain, and individual differences in the mechanism of pain control. When using the TENS be persistent and patient and discuss any concerns you have with your Physical Therapist.
Many patients report good-to-excellent results, first with pain control, then pain relief, and finally with a reduction in the use of medications. Although it doesn’t happen for everyone, some chronic pain patients are “cured” permanently from their pain.
As each of these benefits from the TENS treatment occur, you may find yourself increasing your activity level either with the same level of TENS usage or even with reduced frequency of use, intensity of signal, or duration of time that the unit is turned on.
If for any reason your pain starts to increase in frequency, duration, or intensity, don’t assume the treatment isn’t working for you. First, check the TENS unit for any malfunction, the need to recharge the batteries, or the need to replace the electrodes with new ones. If your unit is battery-operated, you may find it necessary to turn the intensity up to obtain the same sensation when the batteries are low. This should alert you to the need for battery replacement.
Finally, be aware that some patients experience “breakthrough pain,” referring to a situation in which you get pain relief at first with the TENS unit but then for some reason even with the TENS unit on you again start to experience pain. Needing to turn the intensity up high enough to cause muscle contraction is an indication of breakthrough pain.
Sometimes a different setting for the stimulator may be needed when breakthrough pain occurs. Most units have a setting that allows for random pulse frequency, duration, and amplitude. The use of this setting helps keep the nervous system from getting used to a specific amount of stimulation and becoming accustomed to it, which is called habituation or adaptation.