Neuromuscular electrical stimulation (NMES) reduces structural and functional losses of quadriceps muscle and improves health status in patients with knee osteoarthritis. J Orthop Res. 2013 Apr;31(4):511-6.
From the study:
“OA patients presented smaller vastus lateralis thickness (11.9 mm) and fascicle length (20.5%) than healthy subjects (14.1 mm; 24.5%), and also had a 23% smaller knee extensor torque compared to the control group. NMES training increased vastus lateralis thickness (from 12.6 to 14.2 mm) and fascicle length (from 19.6% to 24.6%). Additionally, NMES training increased the knee extensor torque by 8% and reduced joint pain, stiffness, and functional limitation. In conclusion, OA patients have decreased strength, muscle thickness, and fascicle length in the knee extensor musculature compared to control subjects. NMES training appears to offset the changes in quadriceps structure and function, as well as improve the health status in patients with knee OA.”
“The intervention program promoted a reduction of 38% in joint pain, 29% in joint stiffness, and 34% in functional limitations.”
- Wave form: rectangular biphasic symmetrical
- Duty Cycle: 10s on 50s off, with lessening rest period over time to 10s on 20s off the last 2 weeks
- Duration: 18 minutes
- Rate: 80 Hz
- Pulse Duration: 400 uS
- Intensity: maximum comfortably tolerated
- Electrodes: two 5×13 cm (65 square cm)
- Training Frequency: 3 x per week for 8 weeks
What’s interesting about this study is researchers were not using EMS to recover from surgery as in the recent total knee replacement (TKR) blogs I have done but used it as a stand alone treatment on those with knee osteoarthritis (OA), to see what effect they would get without the replacement. Results were pretty good with regards to increasing strength and function as prior research would suggest, but also interestingly decreasing pain 38%. Which agrees with my observations that EMS type currents work to decrease pain as well or better than TENS type currents, and you get the two for one benefit of improving muscle performance.
While strength training exercises are generally well tolerated in those with osteoarthritis, and I used them regularly with my physical therapy programs, I do have to closely monitor intensity levels and exercise selection to maximize strength gains and minimize any increases in pain. EMS gives my patients a large boost as I can generally get strong muscle contractions with minimal joint stress while it significantly lessens pain. Also many patients who are seeking physical therapy have muscle inhibition secondary to pain and may not be able to voluntarily contract their muscles hard enough to maximize strength. This combined with the expense of therapy and limitations from insurance plans, does not allow full recovery of function in their allotted number of visits. In such cases,doing EMS at home in addition to and beyond physical therapy helps to maximize functional return. The decrease in pain combined with the increased strength can then lead to greater physical activity and health, which goes a long way towards improving outcomes should the patient require joint replacement later down the road. I was speaking with an orthopedic surgeon yesterday who specializes in partial and total knee replacements and he said a mild to moderately arthritic knee still works better than a replaced knee so if if you can continue to stay and active and live with a little pain, you are better off for it.
I do want to talk about the treatment parameters of the study. Rate and pulse duration sound good, duty cycle started off 10s on 50 off, which is my go to duty cycle but they progressed it down to 10 on 20 off over coming weeks, which may be better, or may be why the researchers were only able to increase knee torque by 8%, which is on the low side (but could also reflect the fact that these knees are still arthritic). 10s on 50s off 10 times was the favorite of Kots and the old Russian stimulation parameters from which sports conditioning with EMS began. The idea is that being that a long 50s rest gives you enough time to fully recover between contractions so that the muscle can contract maximally with each repetition. Bringing the rest period down to 20 seconds according to Kots, and according to my experience causes a build up of fatigue so that subsequent contractions are weaker. However I notice that each time the contractions weaken, if you have a powerful enough machine you can turn it up and get a stronger contraction, apparently reaching deeper fresher muscle fibers with the increased current. In theory I could see this resulting in still better strengthening but this is still untested as far as I have seen. I think you would really need a randomized controlled trial to tell because as a user you just feel yourself getting fatigued, and it takes weeks to tell if you are getting stronger and even then it is difficult to compare yourself to other duty cycles you have done or could have done due to many confounding variables. So as of yet the science is not there, at least not in English, so some sports conditioning coaches using EMS are varying routines loosely based sports conditioning periodization programs. Interestingly, most of the European preset programs for muscle strength and hypertrophy are using shorter rest periods, and generally shorter contraction times as well, but I have yet to see any research demonstrating them superior to the Kots duty cycle. However, EMS is becoming a fairly hot area of study for sports conditioning and recovery so I would expect some of these answers to emerge sooner rather than later.
I’ll also comment that this is one reason why I like programmable EMS units, rather than ones that have only preset programs. Programmable machines allow for endless variety and experimentation and If new research comes out with a new duty cycle, and your EMS unit is programmable, like the EV-906 or the upper level Globus models you can instantaneously program those parameters into your machine and there you go. If your machine only has preset programs you are stuck with them, some are better than others, and a lot of them don’t allow for duty cycles anywhere near the ballpark of what is generally found successful for strengthening. For example, so far none of the preprogrammed EMS units I have reviewed allow for my, Kots’, and famous track coach Charlie Francis’, preferred 10 on 50 off duty cycle.
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.