I did an electric muscle stimulation workout, and my left butt cheek has never felt more alive

I'm wearing a thick black vest, which is connected to a series of wires running to my arms, legs and glutes. A thick cable connects the vest back to the Miha Bodytec machine, a German training machine that intermittently delivers four-second bursts of electricity to individual muscles. My lats, middle back, lower back, glutes, quads, biceps, pectorals, and abs are all receiving direct electrical charges.

This is the future of fitness, at least according to Mohamed Elzomor, the trainer manning the Miha Bodytec at Manhattan’s Core Club. He’s taking me through an Electric Muscle Stimulation (EMS) workout. The theory behind EMS is simple: when electricity stimulates your muscles for you, you can recruit more muscle throughout your entire body for every rep.

EMS isn’t new; it’s been used by physical therapists and rehab specialists for decades. But in recent years, it’s become such a popular workout recovery tool that several kits (such as PowerDot and the Marc Pro Plus) are now easily available for purchase on Amazon. It's also a hot trend among several Victoria’s Secret models like Alessandra Ambrosio and Alina Baikova, who routinely join Elzomor for sessions at the Core Club.

To be clear, Elzomor isn't claiming that his shock box contains any muscle-building or fat-burning magic — which is a good thing, too, because existing research lends limited support to EMS recovery and training techniques. One 2017 study of 21 male cyclists found that four weeks of EMS work didn't noticeably impact strength or endurance. Another study found that EMS could improve squat performance — but it was best used if paired with more standard training methods.

While EMS has been gaining ground in Europe, now the trend is set to take the United States by storm. Elzomor, who says he’s one of three U.S. trainers certified to use the Miha Bodytec, says that by next year, you’ll see SoulCycle-esque EMS gyms offering “group” workouts. I wanted to find out whether it was legit, so I decided to try it for myself.

Elzomor gets things started by firing up each muscle group at a time, delivering test pulses to figure out how much I can take. I feel each pulse cause tiny spasms in targeted muscles, and I notice my imbalances: my left lat is less responsive to the pulse than my right, and my left glute doesn't want to fire at the start.

During the workout, I'm suddenly aware of those muscles, and I work hard to contract my left glute. But after the plank, as I get into a squat hold, I'm reminded of why this workout doesn’t measure up to a true HIIT or weight room session. There are no truly challenging muscle-building exercises here. Instead, I’m holding a low squat.

The entire time, Elzomor has me talking. He wants to know if the charge running through each muscle is too high or too low, or if it’s painful. I tell him it’s not, but the conversation is important: it’s the only way he can gauge whether the current is challenging me enough.

When the electric pulse hits my body, Elzomor has me flex my chest and biceps hard. We eventually progress to a split squat hold, and while this is challenging under the EMS pulse, it’s not nearly as hard as, say, a set of 225-pound deadlifts. He doesn’t use weights because he says that with your muscles in slight spasm, they’re not in an ideal (or safe) position to be overloaded with weight. The impulses to my biceps, Elzomor says, are prompting 85 contractions a second. That doesn’t leave my arms ready for the single, controlled contraction needed to curl a 35-pound dumbbell.

This is where EMS falls short: if you can’t train with progressive overload, you can’t truly pack on muscle. The closest Elzomor comes to taxing my body with resistance comes three days later during my second EMS session, when, after a no-weight triceps kickback, he places his hands on my arms to offer light pressure.

I do some isometric exercises, but they don't jack up my heart rate enough for true cardiovascular benefit. While I do wind up in a pool of sweat at the end, my heart rate, as measured on a WHOOP wristband, never exceeds 162 beats per minute, far less than my high-intensity interval training session.

When we wrap up with bicycle crunches and sit-ups, I discover that the abdominals on my left side are slower to fire than the abs on my right side. When receiving that regular electrical impulse, they fire more cleanly, leading to a deeper burn on my situps.

Could an EMS challenge a regular out-of-shape dude? Sure. So could a half-hour of HIIT, SoulCycle, or yoga, at a fraction of Elzomor’s $145-a-session cost at the Core Club.

Two 20-minute EMS sessions have me convinced that this won’t revolutionize your training life. BUT What EMS can do well is what Elzomor claims: it can support your other gym efforts by enhancing your mind-muscle connection. He says he trains many of his clients with standard gym practices, then supplements that work with twice-a-week EMS sessions. “You need to do more than EMS [to see a difference],” says Elzomor. “You still have to go to the gym.”

EMS can also potentially enhance your ability to make certain muscle groups "fire." Often, desk jobs and sedentary lifestyles cause underutilized muscles to become less responsive; if you work in an office and don't regularly work out, there's a good chance that your lats and glutes, muscles that lengthen during sitting, aren't as "active" as they should be, which can hurt your posture. 20 minutes of EMS can help activate those muscles and build body awareness.

EMS is fun, and it’s a valuable tool in helping you uncover muscle imbalances. But it’s no muscle-building or fat-incinerating miracle. Still, I’m dying for another session to keep exploring my imbalances, like that sleepy left glute I found during the first workout. That's the type of thing that high-level athletes and obsessive-compulsive gym-goers will pick up during EMS training. Basically, it's a tool that lets you explore your body, finding deficiencies that you can address in your other training — at a regular, old-fashioned gym.