Another client gets blasted in the cryo-sauna. Photo: Bobby Doherty

“You may now start to hyperventilate and shiver uncontrollably,” I hear. Other than undergarments, I am wearing nothing but athletic socks and clogs on my feet, raw-wool mittens on my hands, and a post-concussive expression on my face. I am ensconced in a shoulder-height cauldron spewing nitrogen-iced air at minus-264 degrees Fahrenheit.

The woman talking is Joanna Fryben, co-owner of KryoLife, a year-old spot off Central Park South that specializes in whole-body cryotherapy — a three-minute treatment said to burn up to 800 calories, release an eight ball’s worth of endorphins, improve sleep, boost the immune system, reduce inflammation, smooth wrinkles, and solve the Israel-Palestine conflict.

Fryben is 40 — a Cameron Diaz 40. She has not been sick in four years, about the time it’s taken her to bring WBC from her native Poland (it’s popular and even covered by health insurance in much of Europe) to New York, where KryoLife is the only game in town.

But that may soon be changing. “When we opened our beta site in 2012, there were maybe six other cryotherapy centers in the U.S.; now there are at least 30,” Fryben notes. Dr. Aran Degenhardt, an integrative physician who’s referred chronic-pain patients to KryoLife, says he’s also noticed an uptick, “probably because there are more celebrities and high-profile athletes using it” — like Demi Moore and Kobe Bryant.

A framed article along KryoLife’s entryway touts Cristiano Ronaldo’s at-home cryotherapy chamber (the treatment, originally developed by a Japanese doctor in 1978 for rheumatoid-arthritis patients, has been more recently adopted by pro athletes seeking ice-bath-like recovery). But aside from jocks and joint-pain sufferers, Fryben’s broader goal is to target more self-help-inclined fools, like me, who have fit bands on their wrists and bone broth in their fridges.

A full minute into my deep freeze, I am neither hyperventilating nor convulsing, just feeling numb from the waist down. At these extreme temperatures, allegedly, the air no longer contains moisture, so cold does not penetrate the skin like it does in, say, Siberia; according to Fryben, three minutes or less in here is safer than a hot sauna. To distract myself from the cold that is penetrating, as I peer down from my perch inside what looks like an open-topped Coke can, I chat up Fryben like an undermedicated child: “Should I be standing very still?”; “Do you normally talk people through the three minutes?” I am short of breath. Words are coming out, but my face is not really moving.

And just like that, the three minutes are up. I emerge Godzilla-like from my enclosure feeling … wow, I did not expect to feel so great. I am gabbing relentlessly as Fryben guides me to an Airdyne bike, where I’ll spend the next five minutes warming up my muscles. My skin temperature has dropped to 32 degrees Fahrenheit, and science would suggest (although major cryotherapy studies are still in short supply) that my body has incinerated calories in the quest to restore homeostasis.

“Those are the endorphins,” Fryben explains when I ask about my Mountain Dew rush. “You went into a stressful environment, and your body reacts in a way to protect itself. The immune system is boosted, the lymphatic system moves, the blood is oxygenated — enzymes and nutrients are delivered to every part of the body.” Degenhardt likens this fight-or-flight response to a runner’s high.

People I meet at KryoLife speak to various other benefits. An arthritic client named Nicola says the swelling and pain in her hands have gone down significantly since she started coming here (she does batches of ten sessions punctuated by three-month breaks, the recommended course for jump-starting the nervous system). Eduardo Bohórquez-Barona, a KryoLife associate and former caffeine addict, says, “I’m Colombian; we need coffee. But if I do cryotherapy, I’m energized all day.” I would compare my own state of whole-body awesomeness to the afterglow of a fabulous colonic, with an added kick of adrenaline and a tighter-seeming complexion; co-workers later tell me I look like I’ve just been skiing.

Still, I decide that I would be more inclined to shell out the $90 per session if this place looked less like that unmarked tanning salon I frequented in college. (Fryben assures me that a cushier KryoLife outpost is planned to open downtown in the months ahead.) And then, of course, there are the risks: I had to change into fresh socks pre-sauna because any lingering moisture could cause frostbite. And Degenhardt noted that passing out is a possibility if your blood pressure gets too high or too low. KryoLife gives all ­clients a medical questionnaire and blood-pressure check, but in short: ­Consult your physician before freezing.

When my biking is done, Fryben explains that she doesn’t mandate this post-­treatment exercise for on-the-go New Yorkers. “But if this were L.A. or somewhere you’d be getting straight into a car, that wouldn’t be safe for the joints,” she says. “Because your body, you know — it gets frozen.”

KryoLife, 57 W. 57th St.; 212-551-3333.

*This article appears in the January 26, 2015 issue of New York Magazine.