How a TENS Machine provides Pain Relief


Pain is the body’s warning system. It alerts us to injury or illness. When the body is functioning normally, pain serves as a vital warning sign when something is not right.

Pain signals, in the form of electrical impulses, travel through the body’s nervous system from the site of injury or ailment to the brain. Then, at the brain, these impulses are interpreted as pain.


There are two main methods that a TENS machine uses to provide you with pain relief.

  • Pain Gating
  • Endorphin Release

Pain Gating

There are millions upon millions of small nerve fibres throughout our bodies which allow the sensation of pain to be felt. As well as these, the human body is also equipped with thicker nerve fibres. These carry less unpleasant sensations such as warmth, touch and the position of our joints, helping us to form an impression of our environment.

The sensation of touch is particularly relevant when considering pain, since as we know, if someone accidentally knocks their elbow, they instinctively rub it. This rubbing action excites the larger nerve fibres, which in turn, have an effect on the transmission of signals from the smaller “pain-carrying” nerves. Luckily, your brain can only interpret a limited amount of information. If the “rubbing” sensations outnumber the painful “bump” sensations, the brain will interpret the sensations as being from the pain-free rubbing source rather than the painful bump. In other words, the rubbing sensations have ‘bombarded the gate’, so painful messages cannot get through.

The Gate Control Theory was initially proposed in 1965 by Melzack and Wall based on the fact that small diameter nerve fibres carry pain stimuli through a 'gate mechanism’ but larger diameter nerve fibres going through the same gate can inhibit the transmission of the smaller nerves carrying the pain signal. This theory lead to the development of TENS units which are designed specifically to stimulate the large nerve fibres.

Endorphin Release

According to the second theory, T.E.N.S. stimulation encourages one’s body to produce and release greater amounts of a chemical called endorphin. Endorphins are our body’s own natural painkillers that are released as a natural function to overcome pain. Endorphins interact with pain receptors, blocking the perception of pain, much as the pharmaceutical drugs or narcotics such as morphine do, but without the side effects associated with these types of drugs. . Endorphins are released by the descending nerve fibres or nerves which travel down the spinal cord from the brain.

When we feel pain, the descending nerve fibres release endorphins at the spinal cord, where they meet the sensory nerves carrying the 'pain messages’ from our body. This local release of endorphins by the nerves inhibits some or all of the pain messages going up to the brain.

A great example of endorphin release is the natural 'high’ that runners and other athletes experience after 30 minutes of sustained exercise. Much like exercise, the endorphin release stimulated by the TENS may take up to 30 minutes or more to take a noticeable effect. The “feel good” effect may last several hours before endorphin levels in the body need to be increased again.

For more information about TENS machines, visit the Natures Gate website at