By Carl Valle
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 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 electrical muscle stimulation.
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 electrical muscle stimulation is usually confined to a few studies on stroke victims and post-surgical wasting, and nothing I have seen has excited me.
What interests me, instead, are the clinicians who have used EMS creatively. Some of the studies on cellular and performance outcomes are strong enough to show that EMS isn’t just a placebo. I have used the Compex systems for nearly 20 years, and have some experience with the Marc Pro, PowerDot, Globus, and ARPwave. If I had to conclude which I think works best, it will be a short answer: All of them work, so choose one based on your needs and not its features.Choose an EMS device based on your needs, and not its features. Click To Tweet
If you were to go to a medical bookstore and check the physical therapy section on EMS, you would see that it tends to be a set of protocols based on pad placement, current settings, and scheduling sessions. This approach is nowhere near the same as what the modern clinician does and, since we are now entering the bionic athlete era with gait retraining, this only widens the gap between practice and research. It’s easy to shout that you’re ahead of the research, but without evidence, much of what clinicians do becomes like the dated RICE protocol that we still see people clinging to.
A Rapid Review of Electricity for Coaches and Therapists
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 stimulator 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 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.
Experienced coaches and therapists commonly refer to stimulation parameters and share their practices, including the use of different types of settings, such as Russian Stimulation or strength protocols. Stimulation parameters and waveforms can be the subject of their own article but, for the most part, duty cycle, frequency, intensity, and ramp details are part of electrotherapy theory, but are not very well-documented. Regardless of the intimate details, many parallels exist between classic training principles and the current clinical practices of EMS use. Cycles, or waves of energy, are part of a “unified training theory” proposed by several coaches and sport scientists. EMS should be used to improve athletes, similarly to loading the body with training or rehabilitation.
Companies must do their job, not only to prove their machines are delivering exactly what they promise, but also to ensure that their products are used as intended. Most companies have terrible product education, and visiting their YouTube channels makes me cringe more than their highest simulator settings.
The Science of Electrical Contractions With Muscle
Sending electricity through a muscle group sounds like a bad science fiction movie, but that’s precisely what athletes are willing to do to get or feel better. It’s a priority to know what EMS can do physiologically and what is likely ineffective. Five years ago, pioneering researcher Nicola Maffiuletti summarized the differences between a normal muscular contraction and one from electrical stimulation in his NSCA journal article. The two types of contractions have similarities and differences that a coach should know. Overall, EMS is not going to make a major difference. However, like all things in sports training, the little things matter.
One development that throws this concept out the window is the rise in functional electrical muscle stimulation, 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.
Finally, EMS is used to help with neuromuscular adaptations and, while sessions may prevent atrophy, the improvements are from neural drive-like mechanisms, not from increased protein synthesis rates. EMS doesn’t directly create hypertrophy changes to the muscle, and a study on nutrition and e-stim showed no acute changes.
What is also important to know is that electrically stimulated muscles are, for the most part, superficial, and that is useful for propulsive muscle groups. Some rogue therapists are using fine needle EMS with low current for deeper muscle penetration for rehabilitation purposes. Most EMS experiences are one muscle at a time, but some athletes are getting simultaneous total body sessions. Nobody knows if total bodywork is more time-efficient or if a possible synergistic benefit exists, but down the road, studies will likely discover if there is a value beyond convenience.
The Scientific Benefits of Stimulating the Neuromuscular System
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, 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.
EMS and strength, and the results that may lead to jump and sprint performance, are mixed in the research. However, enough research shows that if EMS is done with specific protocols, a positive result is possible, especially with the less-trained athlete. So far, much of the work has been done with soccer, and some recent investigations of youth jumping performance and plyometrics had favorable outcomes.
What was most interesting about the Spanish study from Martínez-López and colleagues was the specific frequency used, as well as the combined approach and specific results. This study was promising, since most of the findings with EMS have involved strength changes but nothing interesting on velocity adaptations. Maffiuletti and Seyri suggested that EMS be used for advanced athletes who need to break plateaus, but so far I have not seen much besides anecdotal reports. I have recently been following some interesting work on the prolonged use of EMS and adaptation to the neuromuscular junction, but so far I don’t think this is a game changer. It could become essential, however, to those less blessed with their nervous systems.
Babault, Cometti, Bernardin, Pousson, and Chatard conducted a gem of a study on French rugby athletes. I love rugby studies because the athletes are highly trained, making it more interesting. In their research, they found great improvements in strength and power. Specific rugby skills like scrum performance testing and speed didn’t improve, but this is not surprising because sport skills and speed with high-level athletes don’t change in just weeks. This is the reason short studies will always frustrate the track coach, who knows that even a year of training is not a guarantee that an athlete will improve with maximal velocity and peak skill performance.
I believe EMS is great for preparation periods and for times when maximal training is difficult to perform during the competitive season. Coaches will see an athlete’s willingness to train and their energy decrease as the season draws out. I don’t like providing EMS too early with athletes because I want everyone to value hard work and sweat. While EMS is not easy, getting off the couch and getting work done is a characteristic and value that athletes must be groomed with early.EMS is great for prep periods and times when maximal training is difficult during the comp season. Click To Tweet
Because EMS can be seen as a “cheat code,” it’s a good way to reward hard training and commitment. Give athletes who have spent years training an opportunity to use EMS. Again, EMS is not a magical solution and it’s limited because the body loves homeostasis and is stubborn to change, especially at higher levels. EMS can help athletes move the needle, but special care in administration is necessary to reap the benefits.
Early Rehabilitation After Surgery
Several studies have shown the value of the immediate use of EMS and return to function. However, this value is difficult to show because weeks of rehabilitation aren’t easy to standardize in research. When someone is cut, even with minimally invasive surgery, scar tissue formation can cause problems with joint motion and edema. We know with other forms of recovery that edema isn’t going to change much without movement. However, due to the nature of surgery, most athletes are caught in the Catch-22 situation of needing to move but being medically encouraged not to.
In addition to the trauma of the surgery, the injury can be a motor control nightmare if the surgery was severe, like a reconstruction. How does electrical muscle stimulation help here? It’s complicated and also difficult to study because we still don’t know everything about the brain, but we are learning.
The strategy of rehabilitation is just good training, but with loading demands taken down a notch. Much of rehab consists of creative ways to remodel injured tissue by progressive overload and rest while trying to work around a compromised joint and muscle system with athletes. Besides placebo, therapists and coaches want to see confidence in movement so the athlete isn’t compensating or guarding against injury or perceived pain. EMS provides an override, forcing the athlete to work during exercise or training when done concurrently with a therapist. The work of Derek Hansen and Bill Knowles has influenced many practitioners and, so far, no reports of this approach not being worth the effort have ever come back to me.
Recovery is a very hot topic and the pendulum is swinging back to training, eating, and sleeping instead of being very modality heavy, or adding activities to accelerate regeneration. Travel is a hot topic as well, since sleep and the strain of being in a plane for hours on end is very exhausting to even the most compliant of athletes.
In the past, recovery was always thought of as some external application of therapeutic modalities, but now it’s the return to natural responses from training. Still, an artificial intervention is essential in modern sport where natural is great for fitness, but the laws of nature are abused for sport. I explained in an article on EMS for the traveling athlete how I use the PowerDot with the athletes I train, but it’s more than just dealing with stiffness of being stationary for long periods—it’s about dealing with the combined challenge of managing long training seasons.
For years, blood flow, lymph flow, and muscle repair were expected from EMS, and the truth is that only through prolonged exposure to EMS will it make sense, and if an athlete is compromised from intense competition and training while on the road. What is important to know is that active exercise may not be recovery to an elite athlete who perhaps just sacrificed their body to inhuman levels of exertion. Sometimes a pool workout during a long season is too much of an emotional burden to do at 3:00 a.m., and it’s just easier to be an “athletic vegetable” and get something done.
Like the edema point mentioned earlier, the need for circulatory action during heavy congestion of the body makes sense if the athlete can do it for periods of time that are longer than the typical 30-minute treatments. Based on the research, a small wearable option called the Firefly can be used for hours upon hours and, based on the anatomical placement, it’s likely a “popliteal lymph facilitation solution.” The slow wave treatments of a Marc Pro are enough to merit a stand-alone investment for athletes or coaches, but the company’s claim that their waveform is creating microcirculation changes is unproven except for a few rat model studies.
The Hype of Biological Electricity and Humans
One problem is that most of the marketing for EMS can turn off coaches (pardon the pun), as it makes athletes believe that near-miraculous changes can occur. Several proponents of EMS have taken the claims a step too far, which is one of the reasons why coaches avoid the use of EMS with their athletes. In addition to its outlandish marketing history, there is a stigma of “only lazy athletes” using an e-stim device. As a lover of all things technological, one paradoxical attitude I have is my aversion to most machines. Like other coaches, I just feel barbells, medicine balls, and a good training surface are enough, for the most part.Previous EMS marketing alienated coaches because it implied that near-miraculous changes can occur. Click To Tweet
Time after time, photos of books like The Body Electric and Energy Medicine appear on social media and in articles as reference, but very few applied solutions surface afterwards. I have read both books and, while they are fascinating, the key question is: What do I do differently with my athletes after reading? While it’s fascinating to understand the marvelous world we live in, a mature and necessary applied solution needs to stem from general reading or it’s merely curiosity-seeking. There’s nothing wrong with lifelong learning, but cargo cult science is a core problem we see in sports training. Because we are still dealing with it, not much has evolved in recent years besides more data coming from slicker technology devices.
As I mentioned earlier, a healthy term to use with EMS is labeling it a “secondary” or “supportive” option to training. Some people like the word “complementary” being used for EMS, but it conjures up a vision of alternative medicine that walks the line of voodoo for me. When presenting EMS to athletes, make sure it’s as something to assist with the primary needs rather than a replacement to conventional training and rehabilitation.
What to Expect When Using EMS With Athletes
EMS is not a cakewalk or fun experience. The sensation of electricity running through my body is not my cup of tea, but at some settings it can be rather comfortable. It takes more than a few minutes to leverage EMS, which is the reason I prefer multiple units to reduce the time of this process. After a few weeks, setting up electrodes during free periods becomes a simple routine that nearly anyone can do. Some muscle groups take longer and are harder to apply alone, like posterior leg muscles and muscles of the back.
Video 1: EMS isn’t painful, but just like a workout, the discomfort is there. The goal with using any e-stim machine is consistency, as all training—including EMS—adds up over time.
One point not often shared is that for more muscle fiber (motor units) to be recruited, the intensity of the current must be higher so it can bleed deep down to below the superficial muscle. Leaner athletes will have an easier time getting into their body because the properties of muscle and fat are much different. Water content makes electrical energy transfer within a body dramatically higher. With any EMS intensity setting, the limit to what somebody can tolerate is very personal and should be athlete-directed, but coach- or therapist-guided.
In “The Top 6 EMS Protocols for Sports Performance,” the actual bread-and-butter protocols will be shared in more detail for managing tissue, rehabilitation after injury, and pushing the limits during maximal strength phases.