The use of electrical muscle stimulation as a shortcut to improving physical fitness was first commercialized sometime in the early 19th century, and while EMS has waxed and waned in popularity over the years, it’s never gone away. Today it is widely used across rehabilitative medical applications but also to boost strength and stamina.
The promise is simple: Stimulate the muscles with pulses of electricity while you’re working out and you can create thousands of muscle contractions in a short amount of time, far more than you can achieve through standard reps. You still have to activate the muscles through flexing and the like—you can’t just lay on the ground and zap your way into shape—but you can accomplish more with a lot less if you’re using EMS as part of your workout.
Studios like Body20 and Manduu now outfit clients with electrodes and pair them with trainers to guide them through EMS sessions. Both companies promise complete body workouts in 20 minutes or less.
The latest spin on EMS is even more appealing: Rather than requiring a studio visit, why not give consumers an EMS suit they can wear at home and use on their own schedule? To that end, German EMS suit maker Pepper offered to let me try out one of its fancy electro-suits to gauge its long-term impact. The company claims that working out while wearing the suit for 20 minutes gives you the equivalent caloric burn and muscle activation of an hour-long traditional workout, all with less strain on the joints.
At least five companies occupy this space at present, ranging from Apeborn’s $4,000 offering to Pepper’s $1,400 suit, which is the cheapest one I’ve found. And even though the idea of getting ripped with minimal effort tickled my lazy bone, it took me a while to come around to the idea of zapping myself on purpose. Could this possibly do any good?
Courtesy of PepperIt turns out EMS has been exhaustively studied—dozens of research papers have been published in the past 20 years—and while results vary, researchers seem optimistic on the whole. One 2021 meta-study determined there is “significant evidence for significant, large-sized effects of [whole body]-EMS on muscle mass and strength parameters, but not on body fat mass.” A 2012 study on trained athletes measured the benefits of using EMS for three to six weeks directly: Vertical jump height increased by up to 25 percent, and sprint times got faster by as much as 4.8 percent.
Another meta-analytical study from 2023 offered perhaps the most compelling commentary, concluding that “eight weeks of continuous resistance training combined with daily upper body, lower body, and abdominal EMS training can significantly improve muscle mass and upper body muscle strength performance, as well as significantly reduce body fat percentage in healthy subjects.”
It all sounds promising, yet despite the extensive research into EMS, there’s no general medical consensus about the tech.
I spoke to a half-dozen physicians about EMS for this story, and opinions varied along quite a wide spectrum. At one end, Andrew Mock, a primary care physician in Newport Beach and five-time winner of the California’s Strongest Man competition, lightweight division, said that EMS had proven beneficial for rehab or critical care situations in patients with severe mobility restrictions, but healthy patients were unlikely to see much value. “If you go outside and start shivering, those are muscle contractions,” he says. “But shivering doesn’t make you stronger.”
At the other end, I heard from Ethan Kellum, the team doctor for the NFL’s Tennessee Titans, who said he uses a form of EMS not just for rehab but to supplement his own workouts. “It’s really a function of the nervous system,” he says, noting that in older patients, muscles can become unresponsive and “go to sleep,” requiring significant effort to reawaken them. “When used appropriately, EMS can help improve the efficiency of communication between the nervous system and the body. Add it to what you’re doing. It can be really helpful.”
Across the board, everyone I spoke to hedged by saying that EMS could, at least for some users, provide some benefit. Perhaps the most representative comments came from Joseph R. Hribick, a professor of physical therapy at Lebanon Valley College. “Current research does not suggest that EMS alone is superior to strength training for developing strength,” he says, “Instead, it should be looked at as a tool to complement strength training and not replace it.”
Suiting Up
Me and my Pepper suit.
Photograph: Christopher NullAfter speaking to Pepper founder Emilia von Keyserlingk at length, I relented. To mimic the aforementioned 2023 study, I would work out with the Pepper suit regularly for two months, three times a week—in addition to maintaining my regular cardio and strength-training workouts and keeping my diet and daily routines the same—and see what transpired.
The suit is a lot like a spring-weather wetsuit that stops at the knees and the elbows. Like with a wetsuit, putting it on can require some effort. Twenty electrodes cover the abs, pecs, glutes, thighs, pecs, biceps, and multiple parts of the back. These are dry electrodes, so you don’t have to wet Pepper’s suit down before you put it on (a common requirement for older gear), but your sweat will improve the conduction of electricity. Of course, if you’re pregnant or need a pacemaker, you shouldn’t use an EMS suit.
Pepper’s suit, available in sizes from XXXS to XXXL, is designed to be very tight so that the electrodes won’t slip into places you don’t want them. Since the suit is intended to be worn with nothing underneath it, that’s a particularly important consideration. And based on the way certain body parts are situated beneath the fabric, it is definitively not something I felt I could wear in public without a cover-up layer.
The only removable part of the suit is a small box that connects at your hip. This is the brains of the operation and its power source. Charge it with a USB-C cable and it’s good for at least 10 training sessions.
Pepper’s app divides workouts into three categories: strength, cardio, and relax, each with a different electrode firing pattern. (Oddly, I discovered that a few workouts were available only in German.) I tried workouts across all of the categories but spent nearly all of my time in strength, as my goal was to build muscle. Strength sessions all involve electricity pulsing through the suit for four seconds, then pausing for four seconds, then repeating for up to 24 minutes.
ScreenshotPhotograph: Christopher NullThe workouts—there are dozens, I rarely repeated any—are tuned to the pulses so that you’re activating muscles across your body while the pulse is on, then usually resting while it’s off. Again, Pepper’s approach is that EMS only works if you are using your muscles while they are being energized, so many of the workouts involve entire body flexes, stretches, and crunches, four seconds at a time.
Plugging In
I’ve experienced isolated EMS for a back injury once before, so I had an inkling of what Pepper might feel like, but the full-body experience is on another level entirely. Fortunately, Pepper eases you in, starting off with soft pulses you can’t even feel. Each of Pepper’s 10 workout zones can be individually controlled, with the power level ranging from 1 to 100. My first video-based trainer said she starts to feel the pulses at level 25, so I slowly ratcheted my way up, bit by bit, until I had all regions hitting around 20.
The shocks on the lower settings don’t really hurt, but you can definitely feel them; powerful, rapid vibrations that shake your insides and sometimes burn a little on the skin. No pain, no gain, right? As I continued to push the levels up, I discovered there was a fine line—really 1 or 2 points on Pepper’s 100-point scale—between tolerable and painful. Those vibrations turned into racy shocks that could be almost paralytic at times, and I spent the rest of my initial 12-minute session dialing the power level back down.
One key discovery is that sweat really matters. When you start your workout, presumably with dry skin, the shocks aren’t as powerful because conductivity is minimal. Start sweating and the shocks increase, even without adjusting the power level in the app. One pulse could be manageable, the next debilitating, just based on how much I was sweating.
My abdominal muscles were the most sensitive to the shocks. Bent over in a crunch position, the contractions could be so powerful in the stomach that I sometimes got a bit nauseous. I was constantly adjusting the levels and ended up with most of my levels around the 30s. To be sure, many of the workouts would be tough even if I weren’t getting zapped.
I asked von Keyserlingk for guidance on the appropriate power level. “The intensity should be high but not too high that you cannot do the exercises in the correct form,” she says. “Being able to breathe normally is key.” Von Keyserlingk says that her levels range from 40s in the lower body to 20s in the back and abdominals—pretty close to my own settings. She notes however that Pepper’s internal EMS expert regularly works out with levels in the 90s. Masochist.
ScreenshotPhotograph: Christopher NullAfter my first workout, I felt good but was happy to peel off the suit, which was sweaty and unpleasant to linger in. (The suit can be machine washed.) If Pepper’s app was to be believed, my short workout burned a whopping 306 calories and earned me 182 “Pepper points,” which are used as the currency for gamified leaderboards across the Pepper user base. By the end of my testing, I could regularly accrue over 1,000 Pepper points per session and have even earned a few top-10 positions on those leaderboards, which are specific for each workout.
After three sessions, I found myself getting more comfortable with the EMS pulses. I also felt soreness visiting different body parts almost at random. On one day my left hamstring was achy. On another, my right biceps was in so much pain I could barely use it. I figured these were all signs that Pepper was doing something—though, again, I alternated standard workouts with Pepper workouts, taking only Mondays off from disciplined exercise.
Considering Gains
Courtesy of PepperTwo months went by. The only workouts I missed were during a weeklong vacation, and I made up the extra time afterward.
The experience was marked by a few problems. After an update, Pepper’s app began glitching and failed to record several of my workouts, costing me thousands of hard-earned Pepper points. Midway through the experience, Pepper released a new, thinner version of its suit with the zipper in front, which the company sent to me. I was excited to give it a try until a piece of the electrical connector snapped off, leaving me unable to connect the battery. The battery pack of suit number three disconnected from the app on two occasions, aborting the workout but at least recording my progress, and it came with an unexpected power boost that left my entire body aching the next day.
Regardless, I muddled through. When the experiment was finished, I’d accumulated 24,000 Pepper points and, purportedly, burned a total of more than 11,000 calories across more than 9 hours of EMS workouts.
To measure my progress, I captured physical data with a tape measure before and after the experience, and I used three different smart scales to further evaluate my stats. All of the scales agreed that the trend line was good: muscle up by 2.7 pounds, fat down by 1.6 pounds—and that’s with smoothed data, since all of these numbers can vary considerably day to day. I added a half-inch or more to my measurements of biceps, thigh, and chest circumference, and my strength was slightly improved, as I’ve been able to add a plate or a few reps to most of my resistance exercises at the gym. Qualitatively, I would say that my physique looks slightly more toned, and I did receive one unsolicited opinion that my arms had better definition. Gains, folks.
ScreenshotPhotograph: Christopher NullWhat didn’t change? My waistline, which I had hoped to improve, didn’t budge at all. While my abdominal muscles feel noticeably stronger, they remain covered by a layer of blubber that is apparently impervious to electricity. That said, the research predicted as much.
Is EMS responsible for my gains, however modest? While there’s no way to say whether my stats improved due to EMS training, my regular workouts, or dietary changes, I think it’s reasonable to conclude that shock tech did have some impact on my fitness level, since my results are in line with what the 2023 study found. I can’t say whether EMS is responsible for 80 percent or 10 percent of those gains, but I think it’s fair to deduce that some good has been happening.
Going forward, I plan to keep using the suit, though perhaps dropping down from three sessions a week to two. If for no other reason than, while it’s great that my level of fitness is improving, the suit has become quite the topic of conversation at social gatherings. I may be able to slack on my personal fitness, but I can’t let down my people.
