Illustration: Matija Medved

Optimize Me

Apparently, Zapping Your Muscles with Electricity Can Make Them Stronger

What to know before you try electrical muscle stimulation

Optimize Me is an Elemental column exploring (and fact-checking) the weirdest self-improvement trends. It comes out every Tuesday.

MyMy senior year of high school, I tore the anterior cruciate ligament (ACL) in my knee playing basketball, requiring me to have surgery and ending my future WNBA career (LOL). During the early weeks of recovery, my physical therapist would attach several electrodes to my quadriceps and run a mild electrical current through the muscle, causing my thigh to quiver and spasm. The logic was that by forcing the muscle to contract, I wouldn’t lose as much muscle mass as I might if I had to wait to begin strength training until my knee could bear weight again.

Fifteen years later, this type of electrical muscle stimulation (EMS) has become popular not only in physical therapist offices but also in boutique gyms around the country. These studios claim that a 20-minute workout using EMS can provide the same results as a traditional 60-minute gym session.

During EMS training, you wear a bodysuit composed of a vest and leg and arm bands with large electrode patches strapped onto the biceps, triceps, chest, upper traps, mid back, lower back, abdominals, glutes, quadriceps, and hamstrings. The electrodes cause the muscles to contract while you go through a 20-minute bodyweight workout including squats, lunges, and planks.

Michka Mirzanejad first tried an EMS suit eight years ago in Germany. After her first workout, she thought, “Well, that was easy.” The next morning, she says, “I felt tight. Two days after that, I felt like I had been hit by a train. I was sore everywhere on my body.” Mirzanejad was so impressed that she eventually bought several suits and opened a studio, Body by Impulse, in her home city of Seattle. “I couldn’t believe a 20-minute workout could give you that kind of muscle fatigue,” she says. “[It’s] such an intense workout, but very doable.”

A killer workout in a third of the time? Sounds too good to be true. So, is it?

While there’s little research on whether EMS can specifically improve the efficiency of a workout, it does appear to increase the intensity, and several studies have shown that people really do get stronger after training with electrical stimulation compared to strength training alone.

There are a couple theories as to how EMS improves strength. One is that the electrical current can recruit more muscle fibers to fire than when contracting the muscle normally. Activating more muscle fibers means a greater portion of the muscle will undergo the microtears that occur during strength training and cause the muscle to heal bigger, better, and stronger than before.

“When you’re doing a voluntary contraction, you’re sending a signal from your brain down to the muscles, and that recruits your motor units — the motor neurons from your spinal cord and the muscle fibers that particular neuron innervates,” explains Diba Mani, a lecturer in the Department of Applied Physiology and Kinesiology at the University of Florida. “With electrical stimulation, you’re [applying] an artificial current, and it’s targeting right over the muscle, so you’re recruiting more muscle fibers directly beneath and pretty close around those electrodes. Just by where your electrical current is going in, you are now increasing or changing which parts of your muscles are being activated.”

While there’s little research on whether EMS can specifically improve the efficiency of a workout, it does appear to increase the intensity.

The electrical current from EMS doesn’t just activate fibers in the muscle—it also travels up to the brain. In fact, among academics, EMS is known as NMES, or neuromuscular electrical stimulation. By sending the electrical activity in two directions — down to the muscle and up to the brain — the therapy can actually strengthen the muscle twofold, making the brain more efficient and effective at activating the muscle fibers. The neuro aspect of EMS is especially beneficial for people who have had a stroke or have a disease that affects the connection between the central nervous system and the periphery, such as multiple sclerosis.

“The strength of the muscle depends on the amount of muscle mass and also how well the nervous system can activate the muscle. You’re engaging both of those things with NMES,” says Roger Enoka, a professor of integrative physiology at the University of Colorado, Boulder. “Sometimes the activation signal [to the muscle] from the nervous system is not sufficient. In other words, it’s less than maximum. So, if you supplement that with electrical stimulation, you can get close to your maximum capabilities.”

Finally, electrical stimulation may act like a form of resistance, making a movement harder than it would be normally.

“Electrical stimulation, you have to tolerate it. It’s almost providing extra resistance,” Mani says. “There’s more resistance you have to oppose to do the exercises you would usually do without resistance, so that means you’re working at a higher intensity, which would potentially mean you’re getting a stronger or better workout.”

Mirzanejad says many of her clients are older adults who have had hip or knee problems and for whom traditional weight training can be painful. EMS can provide resistance without adding weight and pressure on the joints. “Weight-bearing exercise really causes them trouble and doesn’t work for them so well, so this is really beneficial for those clients to help them strengthen the muscles,” she says.

What if you want to spend zero minutes exercising? All the experts interviewed for this article said it’s feasible that you could strengthen your muscles just by shocking them, like I did for my knee when recovering for surgery. However, the benefit is substantially greater when the stimulation is paired with a workout. Plus, you won’t burn any calories or have any cardiovascular benefits without moving.

EMS also isn’t without risk. Enoka says if the muscle receives too much stimulation, it can start to break down and destroy itself, resulting in a serious condition called rhabdomyolysis, so it’s essential to use the technology only with a trained professional.

“People have to be cautious when they do this, and if they’re first starting out, they need to be medically supervised,” Enoka says. “Provided it’s supervised, I think there is a benefit to doing it.”

Health and science writer • PhD in 🧠 • Words in Scientific American, STAT, The Atlantic, The Guardian • Award-winning Covid-19 coverage for Elemental

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