Do TENS Units Really Work?
'Facts NOT Fiction'
TENS units are designed to deliver targeted pain relief through electrical stimulus. Do TENS units really work? Where Is The evidence that they work? What are the facts supporting the use of TENS.
Below I use both scientific and anecdotal evidence to answer the question….
Difficulties With Measuring If TENS Machines Really Work…
Any measure of pain of pain relief is always tricky because of the same simple snag – judging pain is subjective.
Asking people to rate their pain is full of complications.
The first complication is that you will have some element of the ‘placebo effect’ at play – where the fact that you are using a potential pain treatment convinces a percentage of the trialists that they are better, even though their actual pain is the same.
This can be overcome by running the same trial with separate groups. One of whom actually receive the electrical charge and the other group doesn’t.
This works well with tablets where a sugar pill is used in one group and the actual tested drug is used in the other. Both pills look, feel and seem the same.
Trying to ‘fake’ electricity
It is much harder with a TENS machine because you cant create an exact ‘fake’ electrical current, therefore even separating into two groups, will not truly be able to anticipate the impact of the placebo.
The second complication is even more simplistic – that what works for one person will not always work for someone else. So to judge pain levels relies on good size studies to negate the natural fluctuations that could come with any small group.
However, having explained both of the main complications with trying to provide an objective assessment, there is still a lot of clinical data trying to answer the challenge of do TENS units really work.
Do TENS Units Really Work – The Clinical Data….
Of all the various pain relief methods that there are in existence, TENS units are one of the options that carries considerable research.
Research into the impact of TENS machines on back pain, fibromyalgia and osteoarthritis is relatively plentiful.
Unfortunately, primarily for the reasons outlined above and a few others, it is difficult to conclusively prove it’s effectiveness one or another.
As concluded in an update to ‘An overview of Cochrane Reviews’ produced as recently as 2019, small numbers in many of the studies and fairly poor evidence that improvements were down to TENS usage rendered the results unreliable and impossible for them to state anything with confidence.
Low numbers can be an issue because it makes forming definitive dips in pain levels hard to be sure that they aren’t just a statistical anomaly.
Similar to flipping a coin 10,000 times – the expected result would be 50% heads and 50% tails. However, in the total recording, there will be patterns of 10 heads in a row or 10 tails in a row.
If your sample size is only 50 flips and you accidentally select a group with 10 heads in a row, it is likely that you will record that heads is more likely than tails.
Conduct 200 trials of 50 flips however and the outcome will almost certainly end up back at 50%.
The difficulty with medical science is that you could have 20 trials all indicating a preference to one outcome, but you can’t simply join them together to make one bigger trial.
Each trial will have it’s own rules – some are testing fibromyalgia patients, some osteoarthritis patients, others may be testing TENS usage alongside acupuncture etc.
The differences mean in isolation that the results are not significant or conclusive and they are too different to be just clumped together.
If you discount the technical flaws however, and take the individual findings as being enough on their own, then there is significant evidence that TENS units do work.
One, often noted study as an example, was published in the Journal Of Pain and concluded that it definitely made a difference to patients in the short-term suffering with fibromyalgia.
A further review of all the trials published up to 2014 by Vance et al , also reported a definite level of effectiveness. This however, categorised ‘effectiveness’ further by commenting that just how effective a tens machine was depended on a number of factors –
Several clinical trials have observed the fact that using a tens machine on the same frequency day after day, built up a natural tolerance to it.
However, DeSantana et al discovered that to avoid this tolerance being built up, you just need to vary the frequency and the application sites of the electrodes.
b) Optimal Frequency.
Both high and low frequencies have been found to provide different types of pain control.
High frequencies, for example, were found to be better for people already taking powerful opioid painkillers (morphine etc)
Surprisingly, the review also noted the benefit of using a TENS machine during physical movement.
Overall, and perhaps most importantly, the review noted that both high and low frequency usage did in fact provide analgesia (pain relief)
“….have been shown to provide analgesia specifically when applied at strong, non-painful intensity”.
Interestingly, another key finding was that when the electrodes were placed at common acupuncture points, it actually further increased the effectiveness of the electrodes.
However, this was largely contradicted by Brown et al in December 2007 who experimented with numerous electrode placement areas and found no difference on the level on ischemic pain.
Summarising The Clinical Data.
If you take away the clinical need to be absolutely ‘certain’ about something before announcing an official conclusion, (and therefore forgive the trials for not being large enough or perfectly designed), then there is significant evidence that TENS units do work.
However, perhaps the biggest vote for their effectiveness in modern medicine is the amount of traditionally-sceptical family doctors that now have them in their surgeries. In many countries, a TENS machine is now a fundamental part of a family doctors surgery.
It is not uncommon for people with nerve-related pain to be sent for a series of sessions to see how they get on. It is also not unusual for doctors to recommend use of a TENS unit at home.
Now of course, without a commercial arrangement, I do not have a long list of doctors willing to put their name forward to support TENS units.
However, the sheer volume of TENS units on the market and the amount of doctors I’ve worked with that do have one in their surgery, leads me to a safe conclusion that there is definitely benefits for pain relief.
How Likely Is A TENS Machine To Work For Me?
This is impossible to say exactly as results vary from person to person, depending on the pain itself and the bodies’ individual response to the electrical pulses.
One thing to be mindful of is that TENS machines work by transmitting a pulse through the nerves in the skin. If, for whatever reason, you have numb patches of skin, these must be avoided for the machines will to work.
Similarly, damaged, scarred or openly wounded skin will not transmit the electrical pulses as well and may actually start to hurt more themselves.
Every individual is different, so I could not reasonably say that a TENS unit will work for you – just that they do work for a lot of people if applied properly.
It is also worth reading our article on ‘What does a TENS machine do’ – specifically the section on ‘what makes a good TENS machine as different units vary greatly.
Just as poor usage will affect your results, so could a poor purchase, but hopefully my guide will ensure neither of those things happen.
The Final Word –
Do TENS units really work?
Yes, in my opinion they do.
Not for everybody, but no form of pain control (even painkillers) can claim to work for everyone.
Unfortunately, there are some flaws in the quality of the clinical data available. But if you takes the results on face value and combine that with the precedent set by family doctors now using the units, it is reasonable to assume they can be highly effective.
Furthermore, given that you can increase their efficacy by purchasing wisely and following the guidance well, it is not unreasonable to assume that diligent individuals are likely to get a good result from a TENS machine.
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1. William Gibson, Benedict M Wand, Catherine Meads, Mark J Catley, and Neil E O’Connell. (2019). Transcutaneous electrical nerve stimulation (TENS) for chronic pain ‐ an overview of Cochrane Reviews. Cochrane Database.
2. Dana L Dailey, Barbara A Rakel, Carol GT Vance, Richard E Liebano, Amrit S Anand, Heather M Bush, Kyoung S Lee, Jennifer E Lee and Kathleen A Sluka. (July 2013). Transcutaneous Electrical Nerve Stimulation (TENS) reduces pain, fatigue, and hyperalgesia while restoring central inhibition in primary fibromyalgia. Journal Of Pain.
3. Carol GT Vance, Dana L Dailey , Barbara A Rakel & Kathleen A Sluka. (2014). Using TENS for pain control: the state of the evidence. Pain Management
4. DeSantana JM, Santana-Filho VJ, Sluka KA. Modulation between high- and low-frequency transcutaneous electric nerve stimulation delays the development of analgesic tolerance in arthritic rats. Archives Of Physical Medicine And Rehabilitation.
5. Brown L, Tabasam G, Bjordal JM, Johnson MI. An investigation into the effect of electrode placement of transcutaneous electrical nerve stimulation (TENS) on experimentally induced ischemic pain in healthy human participants. Clinical Journal of Pain
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