No longer just a staple in physical therapy, electrical muscle stimulation (EMS) is now making its way into workouts, promising to strengthen muscles in as little as 15 minutes—but is it really legit?

By Elizabeth Bacharach
Updated February 07, 2020
Credit: miodrag ignjatovic/Getty

Imagine if you could reap the benefits of strength training—build muscles and burn more fat and calories—without dedicating hours at the gym. Instead, all it would take is a few quick 15-minute sessions hooked up to some wires and, violá, serious results. A pipe dream? Apparently not—at least according to the pros at Manduu, Epulse, and Nova Fitness, some of the many new gyms incorporating electrical muscle stimulation (EMS) into workouts.

“An EMS workout involves the same movements as many other workouts,” says Blake Dircksen, D.P.T., C.S.C.S., a physical therapist at Bespoke Treatments. "The difference is the addition of electrical stimulation to recruit more muscle fibers,” which, in theory, should increase the intensity of the sweat sesh. With little (although growing) research, the verdict is still out on whether these EMS routines are truly worth all the buzz. Read on to get the full download on electrical muscle stimulation.

What is electrical muscle stimulation, exactly? 

If you've ever gone to physical therapy, you may have experienced EMS or "e-stim," to help loosen your tight muscles so they can recover. When used therapeutically, these devices are designed to stimulate nerves that make muscles contract, ultimately relaxing and loosening any tight spots. (BTW, did you know that physical therapy can also boost your fertility and help with getting pregnant?!)

Physical therapists use localized conduction pads or region-specific belts to deliver electrical stimulation to “muscles that are weak, in spasm, or regions/joints that are lacking range of motion,” says Jaclyn Fulop, M.S.P.T., founder of Exchange Physical Therapy Group.

There are actually plenty of these pain-alleviating devices available over the counter and online (also called TENS-transcutaneous electrical nerve stimulation-units), which will run you around $200. (Fulop recommends the LG-8TM, Buy It, $220, But, again, they're designed to work on a specific area, not your entire body and are typically used under professional supervision. Although these devices are generally "safe and easy to use," Fulop would not recommend using them during a workout and, if anything, only "for pain-relief effects after a workout." (Related: These Tech Products Can Help You Recover from Your Workout While You Sleep)

Okay, so how does this differ from EMS workouts?

Instead of focusing on a specific body part as you’d do in physical therapy, during EMS workouts, electrical stimulation is typically delivered to larger areas of the body via a suit, vest, and/or shorts. As you exercise (which is already engaging your muscles), the electrical impulses force your muscles to contract, which may result in more muscle recruitment, says Dircksen.

Most EMS workouts are pretty short, lasting only 15 minutes at Manduu and 20 at Epulse, and range "from cardio and strength training to fat burning and massage," says Fulop.

For example, after you slip on your stim ~ensemble~ at Manduu, a trainer will lead you through a series of low-impact exercises such as planks, lunges, and squats. (But, first, you're going to want to make sure you know proper squat form.) Sure it might sound simple enough, but it's no walk in the park. Because the pulse actually acts as resistance, the movements feel much harder and leaving you fatigued way faster. Just like with other training, you might be sore. Overall, how sore you are after Manduu or any EMS training depends on multiple factors, such as the "intensity of the work, the weight used, the amount of time, how much eccentric load was done, and if any of the movements were done in new ranges," says Dircksen. (See also: Why Post-Workout Muscle Soreness Hits People at Different Times)

So, does EMS training work?

Short answer: TBD.

When exercising normally, neurotransmitters in the brain tell your muscles (and the fibers within them) to activate and engage in order to perform each movement. Over time, as a result of things such as injury, overtraining, and poor recovery, muscular imbalances can occur and limit your muscle fibers' activation during moves when they should normally be recruited. (See: How to Activate Underused Glutes aka Dead Butt Syndrome for an example of how this can play out IRL.)

However, when EMS is added to the equation, it allows you to call upon more muscle fibers (including those that have remained dormant). To be safe—so you don't overdo it and risk muscle, tendon, or ligament tears—go with "the minimal effective dose," says Dircksen. "Meaning, once you get a muscle contraction from the stim, that is enough." (Speaking of fitness safety...trainers say to nix these exercises from your routine, stat.)

As long as you don't go overboard, this increase in muscle engagement could result in strength gains. If you use e-stim in tandem with movement and weight, your muscles should get stronger than if you did the moves alone, according to some research. In a 2016 study, people who did a six-week squat program with EMS had greater strength improvements compared to those who did not use EMS.

“By actively participating in an EMS class (rather than sitting and passively letting the e-stim activate your muscles), you’re getting a good workout in, which is chock-full of health benefits,” says Dircksen. (Related: The Biggest Mental and Physical Benefits of Working Out)

Yes, the concept of EMS workouts seems to make sense and, yes, some studies do support claims of boosted strength. However, research (of which there is very little) ranges in sample size, demographics, and findings. Case in point: A 2019 review of e-stim research actually found it was impossible to make any conclusions on EMS training’s effects.

"I think a person doing an EMS workout needs to have realistic expectations, especially if they're using it to cut down minutes on the gym," says Fulop. "EMS can temporarily strengthen, tone, or firm muscles to some extent, but it likely will not cause long-term improvements in health and fitness alone, according to the Food and Drug Administration (FDA)."

Another drawback: Electrical stimulation is "extremely difficult to dose properly," says Nicola A. Maffiuletti, Ph.D., head of the Human Performance Lab at the Schulthess Clinic in Zurich, Switzerland. For this reason, it can present a risk of 'under-dosage' (no or minimal training and therapeutic effects) or 'overdosage' (muscle damage), he adds—and this can be especially relevant in a group class setting.

Are EMS workouts safe? 

“Not all EMS devices are 100-percent safe,” says Fulop. “If you're getting EMS treatment by a physical therapist, then they're trained in applying this particular modality and use regulated, FDA-approved units.”

Although using an unregulated product is not necessarily unsafe or dangerous, it can potentially cause burns, bruising, skin irritation, and pain, according to the FDA. The organization also warns that all those wires and cables could also lead to electrocution. So, it’s essential that you ask the trainer or gym about their devices and, if buying a device, do ample research before pressing “add to cart.” (Speaking of machines to buy,  these are the best ellipticals for a killer at-home workout.)

And if you have a defibrillator or pacemaker, the FDA recommends steering clear of EMS. Pregnant women should also avoid e-stim (except for TEN, which is allowed), particularly on their low back or neck, says Fulop. “This could harm the baby and is not proven otherwise.”

It’s also important to note that studies have linked EMS to an increased risk of rhabdomyolysis (a.k.a. rhabdo), the damage or injury of muscles resulting in the release of muscle fiber contents into the blood, which can lead to serious complications like kidney failure, according to the U.S. National Library of Medicine (NLM). But don't freak out just yet: Although serious, rhabdo is rare. Plus, it's not just a risk once you incorporate e-stim into your exercise routine. You can also get the condition from super intense strength training workouts, dehydration, and going too hard, too fast with a new exercise—one woman even got rhabdo from doing an intense pull-up workout.

Bottom line: EMS workouts sound exciting, and the pros are certainly possible, but keep in mind that supporting research hasn't quite caught up yet. (In the meantime, though, you can always lift some heavy weights!)

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February 19, 2018
Terribly researched and shady article. The writer doesn't even scare away twisting the actual statement of resources she refers to. Here are the 3 points in the article that were poorly researched by the writer and actual reality. (1) The writer talks about "One reporter from The Guardian was apparently traumatized". Sounds terrible but if you actually read the linked report by the Guardian reporter he concludes "It was awful, but what a workout. I mean, I’m writing this the next day and I can’t really move my arms, but I’m still going back next week" He liked it, he was just playing a bit of drama. A completely different statement than the author above put it (2) Then she talks about "rhabdomyolysis" and muscle breakdown. Sorry but if you are leading an active lifestyle and working out you may have felt sore muscles before? That is actually the effect that you want to achieve with any sport and workout. As you train you need to stress your body to its limits, only then you get the positive adaptation that you need to improve and get stronger So if you google "rhabdomyolysis" and what causes it, one of the items on the list is among others "Severe exertion, such as marathon running or calisthenics". So muscle breakdown, micro tears or such are very normal for a workout unless of course you consider push ups as dangerous. (3) When the author of the article above claims that EMS has "limited scientific evidence", it only shows that she did a very bad job in researching EMS, as it is extremely well researched. Just google "Electro Muscle stimulation scientific research" and you get access to a plethora of scientifc studies that confirm multiple times the efficiency of EMS.
April 23, 2017
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