By Corey Levitan

Cryotherapy doesn’t feel like being locked in a freezer. It is being locked in a freezer.

I’ve come to a cryotherapy clinic in Las Vegas for a $50 introductory treatment, and find myself in a shower stall that saturates me for three minutes in a fluffy cloud of freezing liquid nitrogen and a blue disco light.

I’m in nothing but my underwear and the socks and gloves provided by the clinic.

The first minute is cake—it feels like emerging from a swimming pool into winter air.

As the air temperature slowly lowers to -150 degrees, however, a stinging sensation develops on my back and the back of my thighs.

“That’s completely normal,” says Erin*, the beautiful Millennial who walked me back to my treatment room without checking any vital signs, then stayed in the room and monitored me during the treatment. “It’s nothing to worry about.”

The content of Erin’s words are belied by her eyes, which constantly scan mine for full consciousness.

“You’re not feeling dizzy?” she asks no less than four times. “Just remember to breathe and don’t constrict yourself. Get in oxygen and don’t panic.”

Cryotherapy is the latest health craze for marathon runners, gym rats, and, reportedly, celebrities such as Mandy Moore, Jessica Alba, and Howard Stern sidekick Robin Quivers.

The promises are not exactly modest: According to the clinic’s marketing materials, one cryotherapy session eases post-workout muscle soreness, “burns 500-800 calories,” “strengthens the immune system,” is “beneficial against depression and anxiety,” and provides an “instant anti-aging effect.”

Most of that is bunk, according to Francois Bieuzen, Ph.D., a researcher at the French National Institute of Sport, Expertise and Performance and a coauthor of a 2015 review on the treatment.

There is no evidence that cryotherapy may help burn many calories or fight aging, Bieuzen says.

Cryotherapy may help with muscle soreness and speeding up recovery after exercise, according to Bieuzen. Though the research is sparse, it seems that exposing your body to very cold air might reduce inflammation.

The only other claim supported by evidence, he says, is a possible slight benefit for symptoms of depression. Your body releases adrenaline and endorphins in response to the cold, which may lead to feelings of well being, he says.

However, cryotherapy’s benefits can be obtained with “a less expensive and easy-to-use recovery modality,” Bieuzen says.

That modality? An ice bath.

“Ten minutes at 59 degrees, approximately the temperature of water exiting the valve,” Bieuzen says. “If you can put ice into the bath, that will be slightly better, but natural cold water is also very efficient.”

You don’t have to put your whole body in the bath, either—just the sore parts.

(Cold showers are not effective, Bieuzen says, because there’s not enough prolonged skin contact to decrease muscle temperature.)

Unfortunately, I’m only finding this out after my $50 treatment.

“Only 45 seconds left,” Erin tells me as my shivering intensifies. “You’re doing good. Do you feel dizzy at all?”

The reason she keeps asking, according to Bieuzen, is that I could be inhaling nitrogen. The gas has no odor and breathes like regular air into your lungs. Without you noticing, it could easily replace the oxygen your brain needs to stay conscious.

If you faint, you’re in even more trouble because the nitrogen is thicker at the bottom of the chamber, so you’ll breathe in even more of it.

That could kill you, Bieuzen says.

Indeed, a young woman named Chelsea Patricia Ake-Salvacion died of asphyxia at another cryotherapy clinic in the Las Vegas area last year.

Granted, Ake-Salvacion died in a cryotherapy chamber that was completely enclosed. I’m in a cryosauna, a different kind of machine that leaves my head and neck exposed to the fresher air hovering above the numbing nitrogen.

Also, Ake-Salvacion was an employee who used the machine unattended and after hours, so no one else was around to notice anything wrong.

Bieuzen doesn’t believe cryotherapy is that risky, though, as long as the clinic follows safety protocols and monitors the client at all times.

“If the cabin is correctly used, it’s safe,” he says.

The tips of my fingers are now starting to stab with needles, even through my gloves. Erin suggests I tuck them under my armpits, which works a little.

So where are you from?” she tries to distract me.

I chatter out my answer, New York, and joke that I moved to Las Vegas because I don’t like the cold. (She laughs.)

“The shivering is completely normal,” she replies. “That’s when you start burning your calories.”

*Name has been changed for privacy