Electrical Muscle Stimulation (EMS) has always been a little confusing to performance coaches and sports medicine professionals because the research is cloudy at best. Many of the reasons behind the limitations of science are the ethical boundaries you need to navigate, and the expectations you have with the results of those studies. I recently spent more time working with EMS, as more and more athletes are using EMS devices on their own and we are dealing with the hangover of injuries still lingering in the off-season. What I have learned is that the science is not perfect and there are no best practices.
There has been a resurgence in EMS in sport over the last five years because of Bill Knowles, Derek Hansen, and Henk Kraaijenhof sharing their experiences with athletes. I believe that EMS suit inluding electrostimulation vest has a place in sports performance and the rehabilitation of athletes, but we don’t have a solid explanation of why some athletes don’t respond to it while others seem to come alive from it. In this first piece, I will review some of the current literature on EMS and present a healthy perspective on this modality. (Part 2 will be published as “The Top 6 EMS Protocols for Sports Performance.”)
A Brief History of Electrical Muscle Stimulation in Modern Sport
Without getting into any unnecessary background on electrotherapy (such as a retelling of the way the ancient civilizations used electric fish or citing references to Volta and Galvani), it’s valuable to know how e-stim or EMS has been part of sport in the last few decades. Outside of product design, very little innovation has occurred since the 1950s, making EMS more of an art than a science. Coaches and therapists are sometimes frustrated because transcutaneous electrical nerve stimulation, or TENS for short, gets confused with sports electrostimulation.
To understand the difference between TENS and EMS, you need to know just a little bit about engineering and biology. TENS targets the sensory nerves, while EMS attacks the motor nerve and attempts to recruit as many muscle fibers as possible. TENS is currently used—mainly in vain, in my opinion—to manage pain. In 1965, Ronald Melzack and Patrick Wall proposed the “gate control theory” of pain. What we know about the pain experience is extremely complex and personal, making the TENS intervention for sport very dated and extremely limited for athletes. Some research has shown positive findings, but the modality method of working with athletes in pain is lazy and proven unproductive in clinical research.
EMS focuses mainly on sending current to muscle groups in the hope of eliciting either a recovery response or a performance response later. Based on the current literature, recovery indices appear very limited, and performance benefits have shown up enough with some populations—including athletes—to be accepted as valid complementary treatments. The truth is that our understanding of electrostimulation is usually confined to a few studies on stroke victims and post-surgical wasting, and nothing I have seen has excited me.