Neuromuscular electrical stimulation can elicit aerobic exercise response without undue discomfort in healthy physically active adults. Crognale D, Vito GD, Grosset JF, Crowe L, Minogue C, Caulfield B. J Strength Cond Res. 2013 Jan;27(1):208-15.[Free Full Text]
Recent studies have suggested that subtetanic neuromuscular electrical stimulation (NMES) protocols applied to the quadriceps and hamstrings may have potential as an alternative aerobic exercise modality. However, its tolerability and effectiveness in the physically active population has been questioned. The primary purpose of this study was to measure physiological and subjective responses to a modified subtetanic NMES protocol in a physically active adult population. Furthermore, the effect of habituation to stimulation on tolerability, the repeatability of response on separate days, and the differences in male and female responses to stimulation were assessed. Oxygen uptake (V[Combining Dot Above]O(2)), heart rate (HR), blood lactate (BLa), rate of perceived exertion, and subjective discomfort were measured in 16 participants (8 men and 8 women) throughout a subtetanic NMES protocol performed at incremental intensities to subjective comfort threshold on 2 separate days, before and after 9 NMES habituation sessions. Peak physiological responses observed at subjective comfort threshold were consistent with therapeutic aerobic exercise intensities (51.5 ± 10.9% V[Combining Dot Above]O(2)max; 72.0 ± 10.9% HRmax; 4.7 ± 2.7 mMol BLa). Peak V[Combining Dot Above]O(2) and current intensity achieved were significantly higher (p < 0.05), yet perceived discomfort was unchanged, after the period of habituation. However, physiological and subjective responses at equivalent stimulation intensities remained unchanged on different days. Male participants showed higher values than female participants. These results suggest that subtetanic NMES can elicit a consistent aerobic exercise response without undue discomfort and could be considered as an alternative exercise modality. [emphasis mine]
I read this paper maybe a year ago when I was somewhere into my year of electric stimulation instead of weights for exercise and was unable to reproduce their results. I was using my Globus Genesy with 2 pads on each quadriceps and 2 pads on each hamstring as described in this paper and it didn’t work. When upping the intensity my heart rate would maybe increase 10 beats per minute (BPM) but after a couple minutes drop back down to my baseline when it felt like my muscles fatigued out.
The difference I think was due to the type of stimulator. The researchers in this study were using a BioMedical Research Ltd. NT2010 stimulator for which has a unique computer programmed activation such that the same electrodes are not activated together each time but “with a different combination of electrodes from the array being involved in delivery of each of the 4 pulses in a burst” with the idea that varying the pairing of electrodes keeps the muscle contracting without fatiguing out so that heart rate is increased and on the first session they were able to get heart rate from ~78 BPM to 114 BPM and when retested on the 12th session they were able to get the average heart rate up to 134.8 BPM. They did 60 total minutes of treatment per session with of which 10 minutes was a warmup, 10 minutes a cooldown, with 40 minutes at a constant work rate.
A big problem however is that as far as I can tell the NT2010 is a research electrical stimulation machine that is not commercially available, at least not that I can find in the United States so I had no way of verifying the results or using it on myself or with my patients. However, I thought about it and figured the problem with my early attempt using my Globus is that I wasn’t able to get enough muscle mass activated to raise my heart rate up and the muscle fibers I was getting were fatiguing and thus not contracting as hard over the 30 minutes I was setting my machine up for. My solution was larger electrodes, A LOT LARGER! I had some ~5.5×8 inch rubber carbon electrodes, which I think are originally marketed as dispersive, non active and so large as not to be felt, with a normal TENS machine, but with a Globus Genesy programmed with a 450 uS pulse duration, you can sure still feel them. Also I split my channels between right and left legs to keep my electrodes far apart for what feels like deeper more global muscle activation (hoping to lessen fatigue) putting channel 1 on glutes, 2 on quads, 3 on hamstrings and 4 on calves. I’m not a big believer in warm ups or cool downs with EMS so I just start as high as I can take and move up from there. The authors said they found 5 Hz better tolerated than 4 Hz, and I tried 6, 5, and later 4 Hz and they were all equally uncomfortable at high intensities. 5 Hz did get my heart rate up the most, increasing with increased EMS intensity as found in this paper. My results at 5 minute intervals being as follows.
- 0 minutes, 0 mA, HR 55
- 5 minutes, 70 mA, HR 105
- 10 minutes, 70 mA, HR 100
- 15 minutes, 75 mA, HR 116 (turned on fan because I was sweating)
- 20 minutes, 80 mA,, 121 mA (hard to read, hurts a lot 7.5/10 pain)
- 25 minutes turned glutes down to 77 mA, HR 120 (thirsty)
- 30 minutes same mA, HR 126
126 beats per minute is 71% of my max heart rate making it aerobic exercise which I’m sure was burning calories and pretty sure was burning fat, but to be honest it hurt worse than exercise does. Larger electrodes still might make it feel better but I used the largest I was able to find commercially. A different waveform might be more comfortable but so far I am unaware of a better one that the 5 Hz. 5 Hz is basically a low rate TENS pattern sometimes used for pain control, but if you can program your machine to a pulse width of 450 the contractions are pretty stout. The idea being at 5 Hz (plus or minus) you are mimicking the shivering, and with so many muscles going as you sit it kind of feels like you are riding a horse as you literally are bouncing up and down. It was actually pretty interesting to be sitting on a couch reading, breathing hard and sweating. When I got up my couch was wet, which I thought was actually pretty gross, so for later experiments I put down a towel and had the fan running. So it worked.
Did I like it? Not really, but at lower intensities it would feel better and probably still get circulation going well enough to be helpful for those with injuries. Also I intend to try it on patients with quadriplegia as alternative the the electric stimulation bicycles, which are prohibitively expensive and very difficult to set up. A couple of the papers I read using the NT2010 agreed with my experience that the subjects for the most part would rather do real aerobic exercise so EMS for cardio might be best used where regular exercise isn’t possible or advisable. Such as when injured, in a hospital bed, or for space travel. For all such purposes I would expect it to be very effective. I’d still like to try it with some larger electrodes, maybe 7” x 10” to see what that does about getting the comfort level up. As an aside I once tried riding an electric stimulation bike, an Electrologic Orion, and lasted maybe 15 seconds before stopping it because the pain was unbearable. So I think the Globus 4 channel with big pads might be the answer to cardiovascular exercise and maintaining LE muscle health in those with quadriplegia. Unfortunately due to the lower level spinal cord injury with paraplegia I don’t expect any of the devices discussed would be effective.
For uninjured people I think EMS for aerobics has promise but isn’t yet worked out well enough to be practical. It’s something I want to continue to read about, work on, and experiment with but it’s tough because it’s painful. It feels considerably sharper than EMS for strengthening and my favorite strengthening protocols only run 10 minutes long. For cardio I do a 30 minute program for which the last 10 minutes are particularly punishing. So it needs work and unfortunately that work isn’t particularly pleasant so it’s hard to stay motivated. I’ve done literally hundreds if not thousands of self treatments with EMS for strength, but for aerobics I have only done 5.
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.