What is a Tens Unit?

Transcutaneous Electrical Nerve Stimulation (TENS) units are electrical stimulators. The stimulation is applied to the skin by means of sticky electrodes. Hence the name transcutaneous, meaning ‘existing, applied, or measured across the depth of the skin’. TENS stimulators are used for applying electrical signals through the skin to the underlying nerves. Depending on the intensity of the electrical stimulation, these nerves can possibly conduct the signal to muscles, allowing muscle movement. When people speak of TENS, however, they most often mean its therapeutic effect for fighting pain. Stimulators that are aimed at muscle (re)generation are called Electrical Muscle Stimulators (EMS).

In TENS, the applied electricity can block pain signals and cause higher levels of Endorphins. Endorphins are famous and praised body substances for several of their functions, including improving happiness and killing pain.

So, what is a TENS unit?

Well, I’ve already tried to tell you that. Perhaps this video will be better at explaining what a TENS unit is than I was. After all, a picture’s worth a thousand words. And a video is just a bunch of pictures plus sound.

transcutaneous electrical nerve stimulation for pain relief

In this video, PNS means the peripheral nervous system and CNS means the central nervous system. The peripheral nervous system concerns all nerves in the body that are not within the spinal cord or brain. The central nervous system concerns the brain and spinal cord.

If you would like to know more about the theory behind this way of pain management, have a look at the Wikipedia page about the gate control theory, a theory about pain suppression.

Does TENS work?

Now that you know what a TENS unit is, you might as well want to know whether it works for you. TENS can reduce the pain, but will not remove the cause of your pain. That’s the first note. Secondly, there are many different sorts of pain. A pain specialist can determine whether TENS is an option for you. Thirdly, although TENS-treatment is prescribed all over the world, the evidence for its effects for pain treatment is not that good. This is partly because it is hard to perform ‘placebo-free’ research to this. By this, I mean that it is hard to form different groups that do not know whether they receive the electrical stimulation or not, as you can feel the electrical pulses. There are thus optimists and pessimists about this treatment, as is the case in probably every topic.

A certain percentage of pain specialists prescribe TENS. Depending on your location and insurance, the TENS-device can then also (partly) be reimbursed. This specialist can also explain you how often and with what settings you should apply TENS.

Is TENS dangerous?

TENS is known to be safe. However, there are some contraindications for the use of electrical stimulation. You can find the list of contraindications for using electrical stimulation (including TENS) here. If you are not sure whether you are able to safely apply electrical stimulation, be sure to contact an expert.

How to apply TENS?

Three factors determine the intensity of TENS, as is the case in all forms of electrical stimulation. These factors are Amplitude, Frequency, and Pulse width. These three factors for electrical stimulation are described more specifically here. Many TENS devices have pre-programmed programs, for example for ‘massage’, ‘muscle regeneration’, or ‘pain relief’. In these programs it is often not possible to change a lot of settings, but it is possible to adjust the total intensity. TENS is usually delivered with a high frequency (more than 50 bursts per second) at a low intensity for pain treatment. This way, the stimulation is not strong enough to produce muscle movements, but just causes the nerves to receive the feeling of the pulses. Sometimes, pain-treatment TENS can also be applied at an intensity at which muscles will move, but at a low frequency. This will not bring you functional movements, but just short repetitive muscle twitches.

Further possibilities of Electrical Stimulation

Make sure to check out the further possibilities of electrical stimulation if you’re interested. Many more possibilities with electrical stimulation exist. As you may imagine, the training possibilities with all these different muscle movements are endless. Electrical stimulation can offer beneficial effects after a spinal cord injury, stroke, cerebral palsy, and many more diseases.

Electrical stimulation can be combined with electromyography or with the brain to form a brain-machine interface. Both these techniques can be useful for training functional movements when paralysed. In the specific case of spinal cord injury, there’s this promising technique called spinal cord stimulation, which can also be applied for the purpose of regaining function.


I hope you know what TENS is by now. This is not the only treatment for pain, of course. When it is possible, taking care of the underlying cause is more effective. When this is not possible, TENS could offer a way for you to relieve you from (a part of) your pain. Keep in mind that TENS is only one of the many ways for pain relief. Pain signals can be interrupted by electrical signals, but also by endorphins and distractions, for example. Be sure to check out all means for pain relief and to consult experts about this (if pain is a serious problem for you).

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