A zero-impact, full-body, 20-minute home workout that’s equivalent to over two hours at the gym sounds too good to be true. But that’s what Katalyst, a trendy, celebrity-loved home fitness brand says its sessions can do. The secret? Electricity. Katalyst uses an EMS (electro muscle stimulation) suit to intensify traditional strength-training and cardio moves by recruiting otherwise hard-to-activate muscle fibers.

EMS has long been popular in studios across Europe for its short, effective workouts, and the trend is slowly coming to the States. (Similar technology is also used in medical settings to aid in injury recovery.) But Katalyst boasts the only electro muscle stimulation technology in the United States approved by the FDA for home use—and it currently has a waitlist of over 70,000.

Curious, I tried a week of Katalyst workouts to see if it lives up to the hype.

How electro muscle stimulation works

EMS workouts use a suit containing electrodes to send small electric impulses to the muscles, causing them to contract. It’s not so different from the signals that our brain typically sends to our muscles, says Asha Gallagher, PT, DPT, a physical therapist at Long Island Jewish Valley Stream Hospital, except that this external activation better engages the type-two (or fast twitch) muscle fibers that can be more difficult to access.

“Our brain activates our slow twitch fibers first, and then it will activate our type-two fibers as needed,” Dr. Gallagher says. “EMS is mimicking that voluntary contraction, but it’s easier to engage the larger neurons and the fast twitch fibers, which is why you get everything at once.” This is the science behind Katalyst’s claim that it can activate 90 percent of muscle fibers in the body, which Gallagher says, in theory, checks out: “The benefit of it is the ability to engage muscles that you probably didn’t even know existed,” she says.

What using Katalyst is like

Getting started with a Katalyst session is significantly more involved than your typical at-home workout. First, I put on my base layer, a thin shirt and shorts designed to retain moisture. Yes, moisture, and lots of it: The Katalyst kit comes with a large spray bottle, used to douse the electrodes on the suit with water, as they need to be soaked to conduct electricity.

Then, I put on my suit (a Katalyst team member taught me how to put it on via Zoom prior to my first session), a vest and shorts with electrodes on each of the major muscles. The suit is very tight-fitting, so much so that I felt like my range of motion was limited (I soon learned that this is necessary for the suit to work, and that having full mobility isn’t really important, since the suit is contracting the muscle for you).

After hooking up my battery pack, which fits into the suit’s pocket, I did a short set-up where I determined how strong an impulse I could handle on each of the major muscle groups. (You can adjust the intensity individually for the quads, hamstrings, glutes, lower back, middle back, upper back, chest, biceps, triceps, and abs.) At the lowest level, the electrical stimulus feels like a tickle, or gentle pins and needles. But for Katalyst’s strength workouts, the idea is to set the impulses to a level that causes the muscle to fully contract. You know it when you feel it—the sensation is startling at first, as if your muscle has a mind of its own and is contracting with more force than it would during a normal workout.

In Katalyst’s strength workouts, which founder Bjoern Woltermann says represent the classic usage of EMS, these impulses—and thus full muscle contractions—last for four seconds, then stop for four seconds of rest. Simple movements, like squats, bicep curls, and lunges, are coordinated with the impulses, as demonstrated by trainers in the recorded videos on Katalyst’s app. Trainers increase the intensity of the impulses throughout the workout (the app is connected to the suit’s battery pack via Bluetooth).

The impulses make typically-easy movements much more difficult. Especially as the intensity grew, I was feeling lots of muscle fatigue. Even muscles that weren’t being directly targeted by the particular exercise were working—I found the impulses on my abs, for instance, to be a helpful reminder to engage them at all times.

I was warned that I’d be extremely sore in the next few days, but it wasn’t as bad as I thought (which made me wonder if I was just too scared to turn up the intensity high enough). One thing that probably helped: Katalyst’s recovery mode, where I could lie down and have the suit send very gentle electrical pulses, intended to help flush out lactic acid buildup. Katalyst also has two other workout modes, cardio and power, which feature more dynamic movement and more frequent, less-intense impulses. There are a variety of workout videos in each category, including some with a specific focus (like ACL injury prevention or stability and balance), as well as those based on other types of workouts (like yoga and boxing).

Though I can’t say that 20 minutes of a Katalyst workout left me feeling like I’d done two hours of work at the gym, I did find the workouts to be fun and to fly by—and to be super easy for small home spaces, as they are mostly standing exercises that don’t move around much. On the other hand, though, I found the relatively complex set-up to be a bit of a disincentive to fitting in a session.

Is it legit?

Dr. Gallagher says that Katalyst and other EMS workouts could work well for those looking for a more efficient workout, but more research on the technology needs to be done before she can give a ringing endorsement.

Still, she says that EMS’s low impact on the body—there’s no jumping or external loads like weights—makes it an appealing option for those recovering from injury, living with arthritis, or experiencing joint issues to still get a challenging workout.

Use Katalyst or any electro muscle stimulation device with caution, she says, as too much intensity could lead to muscle breakdown. Don’t use it if you are pregnant, have heart issues, a pacemaker, or any other implanted medical device, and speak to your physician if you aren’t sure if it’s advisable for you to use.

While the FDA says that Katalyst is safe for home use, it’d be wise to try EMS at an in-person studio first, both to have hands-on guidance from an expert, and to be sure that you like it (especially considering Katalyst comes with a steep price tag of $2,385).

One thing’s for sure: Katalyst and workouts like it are only becoming more popular. “We’re going to see devices like this on the rise,” says Dr. Gallagher. “We’re going to see people wanting to use this, and wanting to get that edge.”