By Joe Ascher, PT, DPT
Recently we have seen a real “surge” in advertising for electrical stimulation units directed at “amping” up muscle recovery in athletes. Enough with the electricity puns, but I am writing to provide some background and the science behind the wires on these units. I encourage you to become an informed consumer, rather than just following along with another fitness fad.
Let’s discuss the differences between TENS and NMES units. A TENS, or transcutaneous electrical nerve stimulation, unit does exactly what it is names; it stimulates nerve fibers and does not impact muscle. Substantial research supports the use of TENS for pain relief. A NMES, or neuromuscular electrical stimulation, unit also does what it is named; it stimulates muscle fibers. The research has supported the use of NMES to increase strength and power when applied during training, but using NMES for muscle recovery is a relatively new idea. The basic theory behind NMES use for recovery is that stimulating muscle fibers after training increases local blood flow, and thus increases the removal of metabolic byproducts from muscle breakdown. This buildup of byproducts contributes to muscular soreness and decreased performance.
Unfortunately, not much published evidence on the use of NMES as a recovery modality exists. A systematic review, including 13 studies with varying quality, was published in the Journal of Strength and Conditioning Research in 2014 by John K. Malone, Catherine Blake, and Brian M. Caulfied.1 This analysis compared muscle performance, muscle metabolite levels, ratings of perceived exertion, and self-reported pain levels in NMES recovery, active recovery, and passive recovery groups. The analysis found strong evidence supporting the use of NMES for reducing rating of pain, perceived exertion levels following exercise, and blood lactate levels as compared to the passive recovery groups.1 However, there was no difference between NMES groups and active recovery groups in relation to pain ratings, exertion levels, or blood lactate levels. 1 One study in the review even showed some evidence that NMES may decrease muscle performance after use for recovery. 1 The training and NMES settings varied between the studies in the review, which muddies up the results, and we must consider that only a few studies existed to be included in the review.
What does this mean to you? While NMES can be more helpful for recovery when compared to lying on your couch doing nothing, active recovery such as light jogging, cycling, swimming, or exercise is just as effective, if not more so, than NMES. Since most advertised units sell for $600-$900, you can be confident that you will save some money by going for a nice light jog, swim, or cycle after a tough workout!
1) Malone, John K., Catherine Blake, and Brian M. Caulfield. “Neuromuscular Electrical Stimulation During Recovery From Exercise.” Journal of Strength and Conditioning Research 28.9 (2014): 2478-506. Web.