How does a TENS Unit work for Pain Relief?

Pain comes from electroechemical impulses relaying the pain message. A TENS unit interrupts this pathway. T.E.N.S stands for Transcutaneous Electrical Nerve Stimulation. It is often used to treat low back pain and neck pain. Tens units use a low voltage electrical current to induce pain relief.
How the Tens Units blocks the pain signal
The Tens unit electrodes are taped to the body part that is in pain. For example, if you are having pain in your neck, specifically in the trapezius muscle- you would place the electrode on the trapezius muscle. The electrodes are hooked up the power unit which is about the size of a pocket radio.
There are two types of nerve fibers that come into play: large nerve fibers, and small nerve fibers. Pain signals travels along small nerve fibers. The large nerve fibers are also knows as the nociceptive fibers because they do not tranmit pain. The electrode tranmits electrical current along these fibers. The tens units works by preventing these small nerve fibers from reaching the brain by stimulating the large nerve fibers. The large nerve fibers "close the gate" in the spinal cord, thus giving pain relief. This is the basis of the "gate control theory of pain" whereby called nonnociceptive fibers can interfere with signals from pain fibers, thereby inhibiting pain.

Some tens units have high and low currents. The high current shuts the pain gate and the low frequency current stimulates the nerve that trigger the release of endorphins, the body's natural pain killers.


Tens units can be used at home by the patient directly and they have minimal side effects. If you wear a pacemaker check with your Dr before using a tens unit as this may interfere with its function. Click here to get more information about TENS Units.