Understanding the Mechanism of Whole-Body Cryotherapy

Cryotherapy's roots can be traced back to a distant time and place, much like the events in "The Empire Strikes Back". In the film, the infamous bounty hunter Boba Fett captures Han Solo and decides that freezing him in carbonite is the most efficient method to transport the reluctant pilot to Jabba the Hutt.

As fans of pop culture know, in "The Return of the Jedi," Princess Leia and Luke Skywalker join forces to rescue Solo. After a brief period of blindness, Solo not only recovers but emerges even more confident, quick-witted, and a better pilot than ever before.

Had Solo's extraordinary recovery occurred a decade earlier, it might've prompted scientists to experiment with freezing as a form of therapy. Lacking access to carbonite, they likely would have turned to liquid nitrogen, a substance that, thanks to concert fog machines and "Dr. Who" reruns, was considered cool enough for the task.

Imagine locking yourself in a small room and releasing liquid nitrogen, which immediately transforms into a freezing mist, chilling you to your core. Just a few minutes would suffice before you burst out of the icy chamber, feeling frozen, energized with endorphins, and ready to face the Dark Side.

In truth, whole-body cryotherapy is believed to have originated in Japan during the 1970s when Dr. Toshima Yamauchi placed his rheumatoid arthritis patients in ultra-cold chambers to alleviate their pain.

The therapy then spread to Europe and eventually made its way to North America, where it has become a popular trend among athletes and celebrities. But how exactly does it work? And more importantly, does it actually work?

Cryotherapy in Action

Whole-body cryotherapy is essentially a modern twist on an age-old concept: cooling down is beneficial for you. Athletes often use ice packs to reduce inflammation in sore or injured joints. Some even immerse themselves in ice-cold water, based on the belief that submersion accelerates recovery after intense physical activity.

The idea that freezing your body has health benefits dates back to the late 1800s when Professor Sugarman gained fame as "the human polar bear" for his winter swims in a frigid New York river [source: Fulton County Republican]. Sugarman was a health enthusiast, though it's unclear what specific benefits he claimed from this practice. At least one modern study suggests that people who regularly swim in cold water report improvements in mood and a decrease in chronic pain [source: Huttunen et al.].

Dr. Yamauchi's 1970s breakthrough, which involved replacing water with liquid nitrogen cooled to extreme lows and then releasing it as a mist, was aimed at aiding those with rheumatoid arthritis. The method was adopted by athletes in the Soviet Union and gradually spread. Eventually, it made its way from elite sports to becoming a fashionable treatment in health spas.

While commonly referred to as just "cryotherapy" in popular media, the term should specifically refer to "whole-body cryotherapy" to distinguish it from "local cryotherapy," which is a widely-used and highly effective medical treatment. Local cryotherapy involves using liquid nitrogen to freeze skin or organ tissue that needs to be removed.

Whole-body cryotherapy is a completely different concept. At a cryotherapy center, you'll pay around $40 or $50, strip down to your undergarments, and step into a "cryosauna" or cryotherapy chamber. These chambers resemble a more stylish version of the barrels clowns sometimes wear or, perhaps, a fancy version of the trash can where Oscar the Grouch lives. In essence, your body is inside a tank while your head sticks out through a hole at the top.

Next, liquid nitrogen is introduced into the chamber, where it instantly turns into gas, surrounding you in a chilling mist with a temperature of about minus 256 degrees Fahrenheit (minus 160 degrees Celsius). Sessions typically last no longer than two to three minutes. By using extremely cold, dry gas instead of water, the body is said to cool down more gradually, with the cold only penetrating up to half a millimeter beneath the skin's surface [source: Robinson].

Supporters argue that this treatment not only helps reduce inflammation, but also eliminates toxins, accelerates metabolism, strengthens the immune system, and slows the aging process.

If that's what the advocates claim, what does the science have to say?

The Cold, Hard Facts

What happens to your body when exposed to extreme cold? When you step into a cryotherapy chamber and your skin meets the frigid air, your blood immediately retreats. This is known as "vasoconstriction," where your body works to preserve heat by redirecting blood from your extremities to its core. This is why your fingers and toes feel numb first when you get cold.

After spending four minutes in a cryochamber at a temperature of minus 166 degrees Fahrenheit (minus 110 degrees Celsius), your skin's temperature will drop to around 66.2 degrees Fahrenheit (19 degrees Celsius). As your skin temperature lowers, your nerve activity slows, blood flow decreases, metabolism slows, and energy output diminishes. If you're not careful, frostbite can occur [source: Costello et al.].

A 2015 study examined the existing research on cryotherapy's ability to reduce muscle soreness post-exercise. The researchers reviewed four studies so small that the total participants amounted to only 64. The combined data suggested that while the studies claimed cryotherapy provided some benefit, the actual evidence was inconclusive. The sample size was too small, the participants too alike, the methods too varied, and the data too limited [source: Costello et al.].

In other words, there’s no strong scientific proof that cryotherapy is effective. Moreover, a 2012 study comparing whole-body cryotherapy at the aforementioned temperature with an ice bath at 46 F (8 C) found no significant difference between the two. While the study did suggest that cooling might slightly alleviate muscle soreness, there was no evidence that either treatment aided in recovery. So, if you're bent on freezing to ease the pain, you might as well dunk yourself in a cheap ice bath — it’s far less costly [source: Costello et al.].

Be cautious, though — if your internal body temperature falls below 95 degrees Fahrenheit (35 degrees Celsius), you’re entering mild hypothermia. This happens 25 times faster in water than when dry [source: Rettner]. This is one of the benefits promoted by cryotherapy advocates: since the chamber uses dry air to cool you, the risk of hypothermia is relatively low. However, a cryosauna is not a place for long stays. According to the National Weather Service, at minus 60 degrees Fahrenheit (minus 51.1 degrees Celsius), frostbite can set in within 10 minutes, even with minimal or no wind [source: Sterbenz].

A key note: To date, the only scientifically verified benefit of body cooling is for newborns deprived of oxygen. It appears that mild hypothermia might assist in preventing cell death and trigger genes that protect the nervous system [source: Rosen]. However, the supporting evidence is so specific to this situation that it cannot be generalized to the broader population.

Cryokiller

In July 2015, a woman walked into Rejuvenice, a medical spa in Henderson, Nevada, ready to start the day. While checking on a cryotherapy chamber, she was surprised to find it already running. She turned it off and waited for the nitrogen mist to dissipate before opening it.

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

What had gone wrong? While critics had long questioned the benefits of cryotherapy, it now seemed that the practice could be far more dangerous — potentially even fatal.

Ake-Salvacion, a regular at the spa and an ardent supporter of cryotherapy, was a firm believer in its health benefits. She often used the cryotherapy chamber and was aware that staying inside for too long could be dangerous. Subjecting the body to temperatures colder than Earth's coldest ever recorded could easily lead to harm.

Ake-Salvacion's cellphone was discovered on the floor next to her body. Investigators suggest she might have been using her phone in the chamber, dropped it, and then lost consciousness as she bent down to retrieve it. At that point, she would have frozen. But what could have caused her to pass out?

Nitrogen, which makes up 78 percent of the air we breathe, is often assumed to be safe. However, this is only the case when it's properly mixed with oxygen. The ideal oxygen level is around 20.9 percent. When it dips below 16 percent, the pulse quickens, confusion sets in, and coordination is lost. Breathing air with just 12.5 percent oxygen can cause permanent heart damage, and at levels under 10 percent, unconsciousness and death can occur [source: CSB].

During cryotherapy sessions, the head stays above the gas, but when Ake-Salvacion bent down, she may have submerged her head, inhaling excessive nitrogen and causing herself to lose consciousness. Since she was alone and not monitored, there was no one to help once she fainted. According to the coroner’s report, her cause of death wasn't freezing, but asphyxiation [source: Women in the World].

Freezing Up

The cryotherapy industry currently operates with little regulation. But that may soon change. Chelsea Ake-Salvacion's death served as a wake-up call, yet other injuries have followed. In late 2015, Alix Gunn filed a lawsuit against a cryotherapy center after her arm was severely frozen. She alleges she was provided wet gloves during the treatment, resulting in third-degree burns, permanent damage, and disfigurement. CryoUSA, the center in question, argues that Gunn signed a liability waiver and neglected to ensure her own safety [source: Turkewitz].

However, these are not the first signs of the potential risks of cryotherapy. Back in 2011, Justin Gatlin, the Olympic gold medalist, was training in Orlando, Florida, ahead of the World Championships in South Korea. After winning gold in 2004, Gatlin had been banned for four years for doping. So, in 2011, he was focused on making a strong comeback and challenging the rising star, Usain Bolt [source: AP].

By 9 a.m., the temperature in Orlando had already reached 90 degrees Fahrenheit (32 degrees Celsius), and Gatlin was sweating as he entered the cryotherapy booth. His socks, drenched in sweat, froze instantly to his feet. This led to frostbite [source: AP].

By the time he reached Daegu, South Korea, the blisters and pus on his feet were beginning to heal, but the fresh scars from the cryotherapy session lined up perfectly with the tops of his socks and the backs of his running spikes. Hindered by frostbite, Gatlin was easily outrun by Usain Bolt. However, Gatlin bounced back and in 2015, he ran the five fastest 100-meter races of the year [source: Wharton].

Following Ake-Salvacion's tragic death, Nevada has put forward new guidelines for those using cryotherapy. For the moment, these guidelines are just 'suggestions' and do not carry the weight of law. Dr. Tracey Green, Nevada's chief medical officer, has outlined the following recommendations for cryotherapy users:

In addition, the maximum recommended duration for a cryotherapy session is three minutes per day, with blood pressure being checked before and after. Cryotherapy centers must have emergency kits, defibrillators, and nitrogen monitors on hand, and employees must be trained in CPR. The guidelines also stress that centers should display signs and waivers that explain the risks involved and clarify that there is no scientific evidence supporting the health benefits of cryotherapy [source: Rinkunas].

They could also add: Always ensure someone is there to supervise you — and absolutely no wet clothing allowed!