How A TENS Unit Works
TENS, which stands for transcutaneous electrical nerve stimulation, is a treatment givewn by a physical therapist to reduce and limit pain. It does this without using any type of medication. The unit sends an electrical current through wires, which are attached to electrodes on the skin. The current is sent from one electrode to another, passing through the outer skin without causing harm. TENS feels a bit like pins and needles, though the intensity can be increased or decreased for comfort. TENS electrodes may be worn for a short time to reduce pain, or may be kept on for extended periods throughout the day.
There are a variety of methods which a TENS Unit works to reduce pain. One method is that it disrupts the pain cycle and how pain signals are received and interpreted by the brain. By changing the feeling in and around the painful area, TENS is thought to give nociceptors, which are the nerves that detect painful stimuli, something else to focus on. In this way, using TENS is like distraction for the nerves. By providing a new, non-painful sensation, pain nerves are allowed to "rest," decreasing the amount of painful stimulus that reaches the brain. In this way, TENS does not change the cause of pain, but rather changes the way the brain interprets it in a safe manner.
Another way TENS is thought to work is by sensitizing peripheral nerves. Peripheral nerves are the nerves that extend out from the spinal cord, detecting different sensations. This is more applicable to people with chronic pain syndromes than those with more acute pain sensations. In people with chronic pain, these nerves often become overly sensitive and may send pain signals to the brain even when no painful stimulus is present. A light touch is often powerful enough to cause sensitized pain nerves to fire. Using TENS can help retrain these nerves so that they respond less frequently, sending fewer pain signals to the brain.
An indirect benefit of a TENS unit is that for some people, it decreases pain sensations enough to allow increased activity, which can help reduce pain in itself. During activity and exercise, muscles are allowed to stretch and contract. This has several benefits. It increases muscle strength, increases blood flow to the muscles and decreases the potential for stiffness. Movement is one of the most beneficial pain treatments, and using TENS to control pain can increase a person's tolerance to such exercise.