• Jay Trisko

What Science Says About Cryotherapy and Cold Gyms

Chilly wellness is trendier than ever

Drastically changing body temperature has been a wellness trend for some time now. There are infrared saunas — which warm the body from the inside and are believed to help loosen muscles — and hot yoga, a popular practice performed in rooms heated up to 105 degrees Fahrenheit. But in the last couple of years, exercising in chilly temperatures has started to gain widespread and mainstream appeal for both its fitness-related benefits and the idea that it can build resilience.

Cryotherapy, in which a person stands in a chamber filled with liquid nitrogen that cools the air to minus 200 degrees Fahrenheit or lower, is a niche (but growing) wellness trend that’s estimated to reach a $7 million market by 2026. The sessions, typically around $75 each, last just three or four minutes and are advertised to decrease inflammation, ease muscle pain, and aid in weight loss. At Brrrn, a New York City gym that opened a year ago, the studio is kept at a brisk 50 degrees Fahrenheit with the promise to help gym-goers burn more calories.

As with many health trends, there’s a spectrum of intensity. Wim Hof, a Dutch extreme athlete famous for swimming in ice-covered lakes and running snowy marathons barefoot, has developed a training program for people seeking extreme cold experiences that he says can complement endurance training and provide potential health benefits like “balanced hormone levels, improved sleep quality, and the production of endorphins.” His approach — which is being studied by Dutch scientists — teaches special breathing methods that are paired with gradual exposure to the cold, such as standing in snow barefoot for prolonged stretches of time. The goal is to build up resilience to harsh elements and make peace with discomfort.

“By encountering stress, you are able to change the way your body responds at a fundamental level. It’s much bigger than just the cold.”

Proponents of Hof’s cold exposure trend argue that humans are rarely cold anymore, and that’s bad. People bundle up for the outdoors and use machinery to keep homes at the same temperature year-round. Scott Carney, author of What Doesn’t Kill Us: How Freezing Water, Extreme Altitude, and Environmental Conditioning Will Renew Our Lost Evolutionary Strength,says that as a result people no longer trigger the body’s natural adaptation abilities. “Because we’re so coddled by technology,” says Carney, “we’ve made [these abilities] sort of irrelevant.”

As Carney sees it, even briefly using cold water in the shower can benefit the body over time. “By encountering stress, you are able to change the way your body responds at a fundamental level,” he says. “It’s much bigger than just the cold.”

Brrrn, the cold fitness studio in Manhattan, takes a similar stance. “We wanted people to be stronger mentally and physically,” says co-founder Jimmy Martin. One way to do that, says Martin, is to stop fearing the cold and instead “be friends with it.”

Working out in cold temperatures is often attached to claims of weight loss, reducing inflammation, and even strengthening the immune system. Whether these claims are grounded in science is unclear.

Martin and his Brrrn co-founder Johnny Adamic say their classes — a mix of high- and low-impact workouts that include battle ropes and slide boards — burn more calories than they would in a warmer environment.Their reasoning is that exercising in the cold interferes with homeostasis, the human body’s maintenance of 98.6 degrees Fahrenheit as a constant body temperature. The body gravitates toward this temperature because it’s what the brain requires in order to function properly. In the cold, the body has to work harder to maintain this internal setting, and therefore, Adamic says, people burn more calories.

Some experts contest this claim. “There are no concrete studies showing you’re definitely able to burn more calories in a cold workout environment,” says Snehal Patel, a physical therapist at the Hospital for Special Surgery in New York. When a person is very cold, their metabolism is at most five to six times higher than their metabolism at rest. However, achieving that much of a spike requires immersion in cold water, “which is really, really, really bad,” says Dr. André Carpentier, an endocrinologist at the University of Sherbrooke in Quebec. “You cannot sustain your core temperature in these conditions.”

Less extreme versions of cold exposure — like a winter hike or a cold workout — tend to increase metabolism just one to twofold, says Carpentier. And even if metabolism spikes higher during a winter run, the cold advantage dissipates once the body is warm again, meaning the increased calorie burning from cold exposure isn’t likely to show on the scale.

That doesn’t mean cold gyms and the like are a complete gimmick. Over the past decade, several studies have elucidated how cold temperatures affect brown adipose tissue, also known as brown fat. When this tissue is activated, it has the unique property of burning its own fat content, which could lead to an overall reduction in body fat. Studies have linked brown fat to better metabolic health, and there’s ongoing research into the potential use of drugs to stimulate brown fat activation in people with diabetes and obesity.

Whether brown fat activation definitely translates to weight loss is still unknown. “No one can say right now if you have more brown fat in your body you will lose more weight over time,” says Carpentier.

Making the body cold stresses it out, and that state of stress may be beneficial beyond possible weight loss. As the environment changes, experts say the body’s drive toward 98.6 degrees stimulates the cardiovascular system in healthy ways. “That kind of stimulus,” says Elizabeth Repasky, PhD, an immunologist at Roswell Park Comprehensive Cancer Center in New York, “is kind of like exercise.”

“There is a thousand-year history of the benefits to thermal stress,” she says, adding that many countries have traditions revolving around hot and cold baths, including Japan, Finland, and Russia.

Extreme cold exposure — like the activities Hof embraces — may help stave off infections, some research suggests. In a 2014 study published in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS), Dutch researchers injected 24 people with an E. coliendotoxin that made them sick for a few hours. The 12 volunteers trained in Hof’s method — which involves meditation, exposure to cold, and breathing techniques — showed a greater ability to fight the infection with fewer flu-like symptoms compared to the untrained study volunteers. They also produced lower amounts of multiple proteins associated with inflammation and infection. The researchers said, however, that it was likely the breathing techniques that were the biggest factor. As the journal Nature reported at the time, 30 minutes after the people started their breathing exercises they started to produce higher levels of the hormone adrenaline which is involved in immunity and stress responses.

Cold temperature devotees like Hof, Martin, and Adamic may find their practices resilience-building, but their clients may find investing in a 50-degree Fahrenheit workout has immediate, if less profound, benefits. Bailee Zimmerman, 26, who works as a model in New York, says cold studio workouts leave her less of a red-faced, sweaty mess than other forms of exercise. “I can do a class and then go out to dinner,” she says, “and save the shower for later.”

Altogether, the science points toward working out in cold conditions as good for the body overall. Whether it builds a more resilient person is up for debate.

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