Cryotherapy is Crazytherapy

The original version of this article appeared in the Kelowna Daily Courier on January 10, 2016.

Residents of Kelowna no longer need to step outside in a bathing suit this winter to feel really cold. In exchange for $55 yLiquid Nitrogenou can spend a couple of minutes shivering inside a “cryochamber” cooled to -150C by liquid nitrogen. The new spa offering this “cryotherapy” makes the usual claims that you have read about in this column oh so many times. It supposedly improves the immune system and reduces inflammation, even though these two things are in opposition to each other, and cures a bunch of non-specific and vague problems, such as pain and stress. They also say it makes hair and nails grow thicker but, since they don’t list any references, it’s hard to check those sources.

Their only plausible claim is for temporary pain relief. When skin gets very cold pain receptors are disabled and you feel numb. At -150C skin gets very cold very quickly and exposure for more than a few minutes will cause frostbite as skin cells begin to die. Last year a Nevada cryotherapy spa worker, using a chamber after hours, was found dead the next morning. Officials don’t know why she didn’t get out before freezing to death, but it’s possible she asphyxiated. The chamber air is cooled by nitrogen gas as it evaporates from liquid nitrogen, which is close to -200C. At the nitrogen changes to gas, it warms up a bit and expands more than 6-fold, displacing much of the air inside the chamber. For this reason there is a height requirement, so your head will stay above the fog. It looks foggy because water in the air condenses, like your breath on a cold day. Despite the spa’s assertion that “nitrogen gas is not harmful” breathing any gas with no oxygen in it is pretty much always fatal. This nitrogen is also cold enough to freeze delicate lung tissue if you were to inhale it, so don’t do that. Since gas is a poor conductor of heat, two or three minutes in the chamber are safe for skin as long as you don’t touch anything.

Metal, however, is an excellent conductor so you must remove jewelry and piercings and wear gloves, booties and protection for other extremities while inside.
Cold skin causes vasoconstriction in the dermis, reducing peripheral blood flow in order to preserve heat in the core. This further cools the skin and can contribute to frostbite. The spa’s website states that during therapy “The body draws blood from the outer tissues into the core where’s (sic) it’s cleaned of toxins while adding rich nutrients and oxygen”. This implies that blood hangs out in the periphery, getting low on goodies, until this therapy “sends” it to the core. Of course blood circulates all the time and is continuously cleaned and enriched without the need for desperate measures. Another claim is that “Endorphins are also released which help to decrease anxiety and depression.” It’s possible that endorphins released by your brain, sensing imminent death by freezing, will change your mood for a short time. After therapy your blood is no cleaner and contains no more oxygen or nutrients than before, but your skin will be pleased to resume full perfusion. Claims of “more oxygen” in blood always irritate me. Upon leaving the lungs your blood contains as much oxygen as it can normally hold. You can’t get over 100% saturation unless you are breathing pure oxygen or pressurized air and then you have to worry about oxygen toxicity, as ever SCUBA diver knows. But I digress.
The spa website refers to medical and therapeutic uses of cryotherapy, possibly to justify its recreational use, but the term itself, although sciencey and futuristic, is misleading because it includes all therapeutic uses of cold. Perhaps many athletes and health providers use cryotherapy but mostly they are just using ice packs or cold baths. Certainly a few high profile athletes are using the chambers, but that is not a strong recommendation as they are big consumers of pseudoscience. Warts can be removed with liquid nitrogen treatment and some tumours can be treated by freezing them but these therapies involve killing tissues with cold.

Can more gentle cold treatment be beneficial? For decades it has been dogma that icing an injury shortens recovery time. Icing causes local vasoconstriction, which reduces inflammation and this supposedly leads to faster healing for various reasons. I was therefore flabbergasted to learn that several studies over the last five years have concluded that all those ice packs I used on soccer injuries probably did little to speed healing, and any effects outside of pain relief were likely due to placebo. A 2015 NIH study concludes that “There is limited evidence from randomized clinical trials supporting the use of cold therapy following acute musculoskeletal injury and delayed-onset muscle soreness.” Another 2015 study goes further and says that if we could cool muscles enough to make any difference we would be doing more harm than good. In hindsight it seems foolish to try to prevent the body’s natural response to injury. Another recent Cochrane review concluded that whole body cryotherapy may actually make some pain worse and there is no evidence that it has any therapeutic or curative effects, making chamber cryotherapy seem worthless. It’s also important to note the long list of cryochamber contraindications. Those with circulatory problems are not allowed to partake because abrupt changes in blood pressure, caused by rapid vasoconstriction, are not the best thing for weak hearts or damaged blood vessels.
Spa ads also boast that you can “boost metabolism”, losing up to 800 Calories in one session. According to the American Council on Exercise, intense shivering burns only 400 Calories per hour, a far cry from the 800Cal/3min claimed by the Kelowna spa. Since shivering doesn’t sound like fun these chambers are sometimes called “cryosaunas”. My Finnish friends would wince at this misuse of the term sauna as much as they wince at our mispronunciation (they say “sow-na”, rhyming with Peter Jackson’s “Smaug”.) No self-respecting Finn would use a cold chamber before jumping into an icy lake in winter. Where would the fun be fun in that?