How Whole-Body Cryotherapy Works

Whole-body cryotherapy is essentially a modern variation on an old idea. That idea is that cooling off is good for you. Athletes routinely use ice packs to bring down inflammation in sore or injured joints. Some also take dunks in ice-cold water based on the theory that the submersion speeds recovery from intense physical exertion.

The idea that freezing your rear has health benefits dates back at least as far as the late 1800s when one Professor Sugarman became world-famous as "the human polar bear" for his midwinter dips in an icy New York river [source: Fulton County Republican]. Sugarman was known as a health advocate, but it's not clear what benefits he claimed from the practice. At least one recent study has found that people who swim regularly in cold water report improvements in mood and reductions in chronic pain [source: Huttunen et al.].

Dr. Yamauchi's 1970s innovation of replacing water with nitrogen cooled to liquid form and released as a gaseous mist was designed to help people suffering from rheumatoid arthritis. The practice was picked up by athletes in the former Soviet bloc, and from there it spread. It was only a matter of time before whole-body cryotherapy crossed over from the world of elite athletics to trendy health spas.

While it's often referred to simply as "cryotherapy" in popular media, the practice should be called "whole-body cryotherapy" to distinguish it from "local cryotherapy," which is a much-used and highly effective medical application. When applying local cryotherapy, doctors use liquid nitrogen to freeze skin or organ tissue that needs to be removed.

Whole-body cryotherapy is a different animal altogether. At a cryotherapy center, you'll plunk down $40 or $50, strip to your undergarments, and walk into a "cryosauna" or cryotherapy chamber. The chamber looks a bit like a fashion-forward version of one of those barrels clowns sometimes like to wear. Or maybe it's a bit more like an expensive incarnation of the trash can Oscar the Grouch lives in. In other words, your body's in a tank while your head pokes out from a hole in the top.

Then liquid nitrogen is released into the chamber where it instantly gasifies, and you're enveloped in a freezing mist somewhere in the neighborhood of minus 256 degrees Fahrenheit (minus 160 degrees Celsius). Sessions usually last no more than two to three minutes. Using very cold, very dry gas rather than water reputedly cools the body more slowly, with the cold penetrating no more than half a millimeter below the surface of the skin [source: Robinson].

Proponents claim that the practice not only reduces inflammation, but also destroys toxins, increases metabolism, boosts the immune system and slows aging.

If that's what the enthusiasts say, what does the science tell us?

What actually happens to your body when you cool it? When you enter a cryotherapy chamber and your skin encounters the shockingly cold air, immediately your blood beats a fast retreat. In a process known as "vasoconstriction," your body tries to conserve heat by shifting blood away from your extremities to its core. That's why your fingers and toes go numb first when you get cold.

After four minutes in a cryochamber at minus 166 degrees Fahrenheit (minus 110 degrees Celsius), your skin temperature drops to about 66.2 degrees Fahrenheit (19 degrees Celsius). Your nerve speed slows with lowering skin temperatures, your blood flow decreases, metabolism slows and power output goes down. If you're not careful, you can get frostbite [source: Costello et al.].

A 2015 study reviewed the scientific literature on the claims that cryotherapy could, at the very least, reduce muscle soreness after exercise. The researchers found four studies so small that the total number of participants came to only 64. Pooling the data revealed that while the studies themselves concluded cryotherapy provided some benefit, the actual evidence didn't produce a clear result. The pool of participants was too small, the subjects too homogeneous, the methods too varied and the data too limited [source: Costello et al.].

In other words, there is as yet no good scientific evidence to show that cryotherapy is helpful. Further, a 2012 study comparing whole-body cryotherapy at the above-mentioned temperature with an ice bath at 46 F (8 C) found no difference between the two. And while the study concluded that cooling off might provide some slight reduction in muscle soreness, there was no evidence that either treatment aided recovery. So, if you insist on freezing your buns in order to de-ache, you might as well jump in a tub of ice-cubes — it's a lot cheaper [source: Costello et al.].

Just be careful — if your internal body temperature drops below 95 degrees Fahrenheit (35 degrees Celsius), you've got mild hypothermia. This happens 25 times faster if you're in water than if you're dry [source: Rettner]. In fact, that's one of the benefits touted by cryotherapy proponents. Because a cryotherapy chamber uses very dry air to cool you down, the risk of hypothermia is relatively low. That said, a cryosauna is not a place to hang out. According to the National Weather Service, at minus 60 degrees Fahrenheit (minus 51.1 degrees Celsius) you can get frostbite in 10 minutes, even if there's little to no wind [source: Sterbenz].

One caveat: So far, the only scientifically proven benefit of body-cooling is for oxygen-deprived newborns. It may be that slight hypothermia can help prevent cell self-destruction and activate neural-protective genes [source: Rosen]. But the evidence for this is so situation-specific, it can't automatically be applied to the general population.

In July 2015, a woman walked into Rejuvenice, a medical spa in Henderson, Nevada, and prepared to open up shop for the day. While checking on a cryotherapy chamber she discovered to her surprise that it was already on. She turned it off and let the mist of nitrogen gas clear before opening it up.

Lying on the floor of the chamber was the body of her colleague, Chelsea Ake-Salvacion. Ake-Salvacion was not just dead; she had been frozen completely solid.

What had happened? Skeptics had been questioning the efficacy of cryotherapy, but now it looked as though it could be dangerous, even lethal.

Ake-Salvacion also worked at the spa and was a cryotherapy enthusiast and proponent. She made regular use of the cryotherapy chamber, firmly believing in its beneficial health effects. She also knew that staying too long in the chamber could be dangerous. Exposing the body for more than a few minutes to temperatures colder than the most frigid temperatures ever recorded on Earth is asking for trouble.

Ake-Salvacion's cellphone was found on the floor near her body. Investigators speculate she was using her phone in the chamber, dropped it and lost consciousness when she went to pick it up. After that, she would have frozen. But why would she have passed out?

Nitrogen makes up 78 percent of the air we breathe, which is why many people assume that it's harmless. But that's true only if it's mixed with the right quantity of oxygen. Humans are happiest when we're breathing around 20.9 percent O2. Below 16 percent, the pulse starts racing, confusion sets in and we lose coordination. Permanent heart damage can result when breathing air with just 12.5 percent of the good stuff. And once oxygen levels drop below 10 percent we pass out and die [source: CSB].

During sessions in a cryotherapy chamber, your head stays safely above the gas, but in bending down, Ake-Salvacion would have submerged her head and possibly breathed in too much nitrogen, causing her to pass out. Since she was alone in the spa and nobody was monitoring her, there was no escape once she lost consciousness. In fact, the coroner's report found that she died not of freezing, but of asphyxiation [source: Women in the World].

The cryotherapy industry is largely unregulated. But that might change soon. The death of Chelsea Ake-Salvacion was a big wake-up call, but there have been other injuries. As of late 2015, a Texas woman named Alix Gunn was suing a cryotherapy center for freezing her arm. She claims she was given wet gloves to wear during the treatment and that the result was third-degree burns, loss of use and disfigurement. The center, CryoUSA, says Gunn signed a liability waiver and wasn't ensuring her own safety [source: Turkewitz].

But these are hardly the first signs of potential drawbacks to cryotherapy. Back in 2011, sprinter and Olympic-gold-medal-winner Justin Gatlin was training in Orlando, Florida, for the world championships in South Korea. After his Olympic win in 2004, he had been banned from competing for four years for doping. So in 2011 he was determined to come back strong and compete against the new kid on the block, Usain Bolt [source: AP].

At 9 a.m. in Orlando the temperature had already soared to 90 degrees Fahrenheit (32 degrees Celsius), and Gatlin was sweating when he stepped into the cryotherapy booth. His socks, soaked with perspiration, instantly froze to his feet. Frostbite followed [source: AP].

By the time he arrived in Daegu, South Korea, the pus and blisters on his feet were healing, but the fresh scars lined up perfectly with the top of his socks and the back of his running spikes. Hobbled by frostbite from that cyrotherapy session, Gatlin was smoked by Usain Bolt. Gatlin has since returned to form, and in 2015 he ran the year's five fastest 100-meter races [source: Wharton].

In the wake of Ake-Salvacion's death, the state of Nevada has issued new guidelines for those using cryotherapy. For now, these guidelines amount to "suggestions" and are not legal regulations. According to Dr. Tracey Green, Nevada's chief medical officer, the guidelines recommend that cryotherapy users should:

Further, a single three-minute session per day is the recommended max, and blood pressure should be taken before and after. Cryotherapy centers should have emergency kits, defibrillators and nitrogen monitors, and employees should know CPR. According to the guidelines, centers should also have signs and waivers that explain the risks involved, in addition to the fact that there's no scientific evidence of any health benefits from undergoing a deep freeze [source: Rinkunas].

They could add: Always have somebody hanging around to keep an eye on you — and no wet clothes allowed!