Electrotherapy is the non-invasive use of different types of electrical stimulation to treat different problems. Each works in slightly different ways, depending on the type of probem being treated.
Transcutaneous Electrical Nerve Stimulation (TENS) devices are used to help control both chronic and acute (short-term, often from surgery or trauma) pain. TENS uses two methods to provide pain relief: gate control and endorphin production.
Since nerves cannot carry a pain impulse and a non-pain impulse simultaneously, when the stronger, non-pain impulse overrides the pain signal, this is known as "gate control." TENS stimulation also encourages the production and release of greater amounts of endorphin, which interacts with pain receptors, much as a narcotic does. TENS is very effective in blocking pain and is used to treat painful conditions in the spine, joints, and muscles.
Neuromuscular Electrical Stimulation (NMES) replicates the signals of voluntary muscle contractions, working with the muscle fibers instead of the nerve fibers. This type of movement is used to strengthen and prevent muscle atrophy in patients unable to exercise their own muscles. NMES also helps to move fluid out of swollen tissue in an injured area to help reduce edema and the associated complications.