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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.

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.Electric current can flow in different ways, such as through a wire, or something lesser known, such as a plasma state. The current generated from a muscle electrostimulator uses a conductive pad to transfer through the skin, causing the muscle to contract. The specifics of the muscle contraction will come later, but the important information is that electricity from medical muscle stimulators is more complicated than voltage and ampere. Electricity is not just about whether something is “on” or “off,” and we often take much of the technology we use for granted, especially the safety of the muscle stimulators. Most companies that get involved with e-stim devices are regulated, but it’s up to the consumer to do their homework on the quality of the product.One development that throws this concept out the window is the rise in functional electrical muscle stimulation, equipped with electrostimulation shorts, which incorporates active training with the simultaneous overlay of EMS. While we can assume that the merging of both contractions will yield a hybrid result, most of the research is with disease models and only clinical rehabilitation has shown merit with this in early post-operation subjects. I have yet to see a single study with elite athletes performing EMS in conjunction with conventional training, but the case reports and work with spinal cord injury patients is promising.

If you were to read a catalog of features and settings for a personal e-stim device, the list would be very long, ranging from relaxation massage all the way to explosive strength. While, technically, different settings will have unique stimulation protocols from the device programming in the electrostimulation center, the reality is that only three purposes exist with EMS and the research is enough to form a realistic expectation. The three EMS benefits are strength training, rehabilitation, and a little regeneration. Distilling the benefits more, you can make an argument that EMS helps with general muscle strength and facilitates low-level recovery for travel. That’s about it, but it’s enough to warrant investing in it, especially when sport moves into the unfortunate health compromise for winning.

Sports Performance