Research seems to show that TENS units can relieve pain in several ways. One is at the surface, where the electrodes contact the skin. On the surface and just below it, electrical impulses balance out the nerve activity that transmit pain signals. Those pain signals travel to the spinal cord to a key spot called the dorsal horn. Using a TENS unit has been shown to alleviate the pain at that spot. Certain parts of the brain involved with processing pain also seem to respond to a TENS unit. One area in the brain is called the periaqueductal gray, where pain signals get turned down.

What types of pain can a TENS unit help treat? More acute pain, such as after surgery or a recent injury where there is active inflammation, has been shown to respond favorably to electrical stimulation. For example, a TENS unit can help reduce the pain from a swollen knee that has been newly injured. But electrical stimulation can also help treat chronic pain problems, like sore necks from too much computer use and joint problems like aching knees. Even problems like menstrual cramps, endometriosis, and diabetic neuropathy can be helped.