Experts say the new celebrity exercise trend known as EMS is a lot more flash than it is a legitimate technique to build muscle or lose weight.

When celebrities try out new trends in fashion, fitness, and food, a curious public flock to these crazes with abandon.

Dresses and shoes sell out in moments after they’re spotted on a red carpet.

Quaint corner restaurants become hot-ticket must-tries after a celebrity mention on social media.

It’s no surprise then that even a quirky health trend quickly gains attention among the masses after a celebrity or two tries it.

One current attention-grabbing trend: electronic muscle stimulation (EMS).

Celebrities including Heidi Klum, Elizabeth Hurley, and Madonna have at one time used this practice commonly promoted as an easy way to build muscle without breaking a sweat.

This technique requires users to wear a full suit of electrodes that are hooked up to a machine.

This machine sends waves of electric impulses through the wires and electrodes and into the body’s muscles.

The electrodes are placed on the biggest muscle groups. The impulses cause the muscles to contract tightly. These repeated contractions, proponents of the technique say, equal the same muscle work as high-intensity workouts.

“Typically muscles contract in response to stimulation from our nerve endings, and electrical muscle stimulation provides this from a machine and electrodes placed on the skin,” said Dr. Allen S. Chen, director of physiatry for the Columbia/NYP Spine Hospital and an assistant professor in the department of rehabilitation and regenerative medicine at Columbia University Medical Center in New York. “The impulses that come from EMS stimulation have the same action potentials that come from our nerves, leading to muscle contraction.”

But can electric impulses equal the same benefits as hard work and muscle training?

Few large, well-researched studies of EMS for muscle building have been conducted.

Most reports for this device rely on small tests, many of which are published by manufacturers of EMS devices.

Other reports list anecdotal evidence.

Recently, researchers with the British Medical Journal warned against the regular use of EMS.

They urged governing agencies from multiple countries to begin regulating the use of these devices.

For its part, the U.S. Food and Drug Administration (FDA) requires that EMS devices meet pre-market regulatory requirements.

Among the governmental demands is that the EMS products should be intended for use in physical therapy and rehabilitation settings only.

In the United States, any companies wanting to sell the device for personal use must “show the FDA it can be used safely and effectively in that setting.”

In a statement, the FDA stated that while EMS devices might be able to temporarily improve strength or tone in muscles, “no EMS devices have been cleared at this time for weight loss, girth reduction, or for obtaining ‘rock hard’ abs.”

Robert Herbst, a champion weightlifter and personal trainer who oversaw drug testing of Olympic athletes in the 2016 Rio games, said EMS has some positive benefits, but not for strength building.

“The general consensus, and my personal opinion, is that it may help in healing, but it does not help to build strength or mass,” Herbst told Healthline. “Physical therapists use electrostimulation to increase blood flow to muscles. This promotes healing by sending nutrients to the muscles and flushing out waste products.”

“The only way to cause a muscle to grow in size or to improve strength is to put it under load, meaning to stress it by making it contract and move a weight or push against a corresponding force isometrically,” Herbst added. “The loading causes microtears in the muscles, which the body not only repairs, but it builds that muscle bigger than it was before in anticipation of future loads. Electrostimulation does not have that effect.”

In fact, Herbst said, you would need debilitating and painful shocks to make muscles contract hard enough for the kinds of tears you need to really build muscle.

Physical therapist Matt Likins, MPT, said he does use involuntary muscle contraction, like what EMS causes, in his physical therapy programs in Michigan.

“We do use electrical stimulation to facilitate contractions or strengthening in individuals that have inhibition following injury or surgery, but once normal voluntary contracts are obtained, we stop using the stimulations,” Likins told Healthline.

Likins isn’t likely to recommend this form of muscle training to anyone for any other reason, however.

“The use of electrical stimulation to strengthen normal, healthy muscle is a sham, plain and simple,” he said.

Despite the lack of strong evidence in its favor, EMS is gaining popularity in Europe, Australia, and the United States.

People pressed for time are looking for a quick way to squeeze in exercise, and the promise of shortening hours-long workouts to just a few sessions of electronic stimulation sounds like a great bargain.

But if it sounds too good to be true, that may be because it is.

Still, that might not stop you from wanting to try it.

The good news is EMS is relatively safe.

“Overall, EMS appears to be a safe modality, and in the United States, devices are regulated by the United States Food and Drug Administration,” Chen told Healthline. “Whether or not these devices are effective, or how effective, remains somewhat debatable.”

Herbst recommends you try EMS with a qualified practitioner. These experts are trained to use the devices and reduce your risk of side effects or complications, which include skin irritation from the electrodes, and in rare cases, headaches.

People with pacemakers and cardiac arrhythmias should not use EMS.

Of course, Chen said, if you want to see guaranteed results, you might leave behind the electric impulses entirely and pick up a barbell or two.

“Hard work, exercise, and eating right. Not much has really changed in this realm. Repetitive, resisted contracture of muscles, like old-school weight lifting or bodyweight training, remain the tried-and-true methods of building muscle,” he said.