TENS, More Electric Stimulation is Better than Less

Adjusting pulse amplitude during transcutaneous electrical nerve stimulation (TENS) application produces greater hypoalgesia.Pantaleão MA, Laurino MF, Gallego NL, Cabral CM, Rakel B, Vance C, Sluka KA, Walsh DM, Liebano RE. J Pain. 2011 May;12(5):581-90.

Abstract
Transcutaneous electrical nerve stimulation (TENS) is a noninvasive technique used for pain modulation. During application of TENS there is a fading of current sensation. Textbooks of electrophysical agents recommend that pulse amplitude should be constantly adjusted. This seems to be accepted clinically despite the fact that there is no direct experimental evidence. The aim of the current study was to investigate the hypoalgesic effect of adjusting TENS pulse amplitude on pressure pain thresholds (PPTs) in healthy humans. Fifty-six healthy TENS naïve participants were recruited and randomly assigned to 1 of 4 groups (n = 14 per group): control, placebo TENS, fixed pulse amplitude TENS, and adjusted pulse amplitude TENS. Both active and placebo TENS were applied to the dominant forearm. PPTs were recorded from 2 points on the dominant forearm and hand before, during, and after 40 minutes of TENS. TENS increased the PPTs on the forearm (P = .003) and hand (P = .003) in the group that received the adjusted pulse amplitude when compared to all other groups. The mean final pulse amplitude for the adjusted pulse amplitude TENS group was 35.51 mA when compared to the fixed pulse amplitude TENS group, which averaged 31.37 mA (P = .0318).
PERSPECTIVE:
These results suggest that it is important to adjust the pulse amplitude during TENS application to get the maximal analgesic effect. We propose that the fading of current sensation allows the use of higher pulse amplitudes, which would activate a greater number of and deeper tissue afferents to produce greater analgesia.

My comments:

The above was a good/strong study on optimizing the use of TENS for pain reduction. Patients were blinded and they had control, placebo, standard TENS (starting with a “strong but comfortable” current), and TENS of increasing intensity as tolerated every 5 minutes (but keeping the intensity “strong but comfortable”) over 40 minutes. The idea being that electric stimulation feels strong at first but then feels less intense as time goes on as the patients either undergo:

  • adaptation: action potentials from the electric stimulation decreases over time
  • habituation: where electric stimulation continues to cause action potentials but the central nervous system (CNS) response decreases
  • accommodation: when a rise in membrane threshold potential that is associated with slowly applied depolarization current

In the review sections the authors noted electric stimulation machines frequently have included or allow modulation of parameters, frequency, intensity, pulse width etc., but noted that no studies had confirmed if that strategy was effective. They noted an interferential current treatment study that found that while the sensation of electric stimulation faded over time the analgesic effect did not. So that’s good news. However it has been noted in a lot of reviews of TENS treatments over the years that there was controversy as to TENS effectiveness to reduce pain. This is likely due to many of the early studies applying the TENS haphazardly, letting patients put electrodes where they want and turning up the electric stimulation to what felt good to them and in doing so it was hit or miss whether the TENS reduced pain. As such, later papers found that when TENS intensity was increased to what was “strong but comfortable” the pain reduction was increased and more reliable.

So this paper not only started with a strong and comfortable current, but instructed subjects to increase the TENS electricity every 5 minutes over the 40 minute treatment time, and the finding was that pressure pain thresholds (PPTs) tolerated both between and distal to the electrodes was increased significantly and fairly dramatically (in comparison to controls, placebo TENS and fixed pulsed TENS). It was also interesting that strong and comfortable fixed TENS resulted ~5-13% improvements in PPTs while the intensity increasing TENS increased pain in the range of ~25-50%, with PPTs staying elevated somewhat 60 minutes after the increasing intensity TENS PPTs were still elevated.

So the take home message with TENS is to start high and increase from there. I like TENS for pain reduction, but I can’t say I love it. Electric Muscle Stimulation (EMS) I have a lot of love for, because EMS has been shown to decrease pain better than TENS and increase muscle strength and endurance at the same time. The reason, I think, is largely because EMS is not a strong comfortable current but I tell my patients to take all they can take, which is often more than uncomfortable.  Anecdotally I get pain reductions after the EMS is removed seemingly a lot longer than I used to get with TENS, so it would be interesting to see that tested.

Of the proposed mechanisms describing the lessening of sensation intensity to TENS over time, the authors thought habituation was the best descriptor and that increasing TENS intensity over time counteracted this by activating a greater number of afferent (nerves heading from the periphery towards the brain) fibers to enhance neurotransmitter release in the CNS. This also got me thinking about the on and off portions of EMS in comparison to TENS currents which are generally more constant. On as hard as you can take and completely off, is a pretty extreme form of current “modulation” and that might be another reason for the enhanced pain reduction seen with EMS currents. So still lots of questions, but a lot of work seems to be going into the use of TENS and EMS for rehabilitation, which dwarfs any other physical therapy modality.

As always, if you have any further questions or need for clarifications, please don’t hesitate to ask. Being aware that some of my blog ideas are contentious and occasionally a bit out of the field of my expertise, I encourage my readers to come forth with any questions/comments that are of interest or concern. Your comments are valued and welcomed.

Chad Reilly is a licensed physical therapist, located in North Phoenix, practicing science based medicine with treatment protocols unique and effective enough to proudly serve patients from Phoenix, Scottsdale, Mesa, Chandler, Tempe, Peoria, and Glendale.

2 thoughts on “TENS, More Electric Stimulation is Better than Less”

  1. Hi Chad,

    I have been reading with interest your writings on TENS and EMS. I have chronic back pain and have had my L4/5 and L5/S1 discs removed and fused, as a result of an injury I sustained when I was in the Royal Australian Air Force. My pain is usually in the injury area but does radiate down my buttocks usually the left, into my groin, again left side and then down my left leg and sometimes my left foot. I have been taking many different medications without much relief of the pain. Lately, I have been using a small TENS Unit called a Pain Mate, which is basically a small TENS Unit that sticks to ones back. It has just an up or down adjustment for intensity. I find I get really good relief if I place the unit very close to but just above the injury site, so that the TENS signals interfere with the pain signals going to my brain. I find I get near immediate relief once I have turned the unit on, unfortunately, it only runs for 20 minutes. I have now ordered a EV-906B TENS/EMS Unit, which I think is basically the same unit that you have used. I liked this Unitas it can be run for indefinite periods, rather than just 20 minutes. As you appear to have such a great knowledge of these units, what settings would you recommend for my TENS Unit when it arrives? I have read that lower setting are good for increasing the Endorphin effect, but what I want is the pain signal blocking or as I call it, scrambling of the pain signals. I understand that this is done at a higher setting. Any advice you can give would be very much appreciated. I realise this is a big ask and that I haven’t purchased the unit through your site, but that was because I live in Australia and the economies of distance would not have made it very attractive, although I been looking at the deffent pads that your site sell and may order some of them if it is possible to get them sent to Oz. I very much appreciate all that you have written and to my limited Aussie brain, I don’t proclaim that I completely understand all that you have written. Kind regards from Down Under, Chris Potts

    • Hi Chris,

      I’m not sure if the EV-906B differs from my regular EV-906 but I expect they are pretty close. I use mine with a 10-50-10 program and did a video on how I program them for strength, which is what I use more than 90% of the time for people with back pain. My focus when I first started doing it was to increase core strength with the machine and I was pleasantly surprised that it decreased pain more than normal TENS. However, 10-50-10 might be a bit much for frequent (more than once daily) use to control chronic pain. So for the latter I might use the “M” setting on the machine and see how that feels. Or maybe do 10-50-10 up to once per day and the M setting if needed more frequent or longer than 10 minutes at a time. You might be able to find electrodes on ebay, but good straps are hard to come by, such that I had to have mine custom made. So maybe email my office and ask if it’s possible to ship them. I think I have shipped them to Europe before so we could probably get them to Australia.

      With chronic low back pain I think EMS/TENS are only partial measures. If you don’t change the way you move, your static postures, and improve core/hip strength and endurance then the same thing that happened at L4-5-S1 will end up happening at L2-3. Most of what I have to say about low back pain rehab is in the Q and A that follows this blog. I hope that helps.

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.