Imagine if you could reap the benefits of strength training without logging tons of hours at the gym.Instead, all it would take was 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, ReBalance, and Impulse Fitness, a few of the many new gyms incorporating electrical muscle stimulation (EMS) into workouts.
“An EMS workout involves the same movements as many other workouts. The difference is the addition of electrical stimulation to recruit more muscle fibers,” says Blake Dircksen, D.P.T., C.S.C.S., a physical therapist at Bespoke Treatments in New York City. Recruiting more muscles fibers should, in theory, increase the intensity of the workout. But with little (although growing) research, the verdict is still out on whether these EMS workout routines are truly worth all the buzz. Read on to get the full lowdown on electrical muscle stimulation and EMS workout training.
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.
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. 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,” using them during a workout is not advised and, if anything, should only be brought out “for pain-relief effects after a workout,” recommends Fulop.
Okay, so how is that different than an EMS workout?
Instead of focusing on a specific body part as you'd do in physical therapy, during an EMS workout, 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 range “from cardio and strength training to fat burning and massage,” says Fulop. For example, after you slip on your EMS ~ensemble~ at Manduu, a trainer will lead you through a series of low-impact exercises such as planks, lunges, and squats.
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 leave you fatigued much faster. Just like with other training, you might be sore: Overall, how sore you are after 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.
So, does EMS workout 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 factors 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, you're able 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. Meaning, once you get a muscle contraction from the stim, that is enough," says Dircksen.
"By actively participating in an EMS workout 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. 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.
So 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),” she adds.
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.
Is it safe to do an EMS workout?
"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," she adds.
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. All those wires and cables could also lead to electrocution, the organization also warns. 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.”
And if you have a defibrillator or pacemaker, steering clear of EMS is recommended by the FDA. Pregnant people should also avoid e-stim (except for TENS, which is allowed), particularly on their low back or neck, says Fulop. "This could harm the baby and is not proven otherwise," she cautions.
It’s also important to note that studies have linked EMS to an increased risk of rhabdomyolysis (aka rhabdo), the damage or injury of muscles resulting in the release of muscle fiber contents into the blood, which can lead to serious complications such as 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 workout training 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!)