How does cold air compare to ice water?
Summary
Both cold water immersion and cold air exposure are forms of cryotherapy.
All forms of cryotherapy work by activating the sympathetic nervous system via cold receptors -- primarily on the skin.
Cryotherapy extracts heat from the body, prompting cold thermogenesis.
Cold air has a lower coefficient of heat transfer than cold water. Therefore, cold air cryotherapy requires much colder temperatures to achieve the same rate of heat extraction.
Colder temperatures introduce a risk of frostbite in cold air cryotherapy that is not present during cold water immersion.
Some people prefer cold air because they don't want to get wet, or they do not want to share bath water with other people.
The science of heat extraction
The use of deliberate cold exposure for promoting health and wellness is called cryotherapy. Cryotherapy extract heats from the body. The more heat extracted, the more metabolic work is required to maintain a constant body temperature. For example, when you use an ice pack to reduce swelling around an injury, that's cryotherapy. However, as cryotherapy for the whole body has become increasingly popular among extreme athletes, biohackers, and people seeking relief from chronic illness, lots of people have questions about how to do it best.
There are principally two approaches to whole body cryotherapy: 1) frigid air, as in a cryochamber, and 2) cold water immersion, as in an ice bath or cold plunge. They both work by activating thermoreceptors on the skin to signal vasoconstriction and thermogenesis through the autonomic nervous system. However, cold water is several times more effective for heat extraction than cold air, so to obtain the same amount of heat extraction in the same time as cold water, a cryochamber has to expose the body to much, much colder temperatures.
The most important distinction between cryochamber versus ice bath is the risk of frostbite.
The much colder temperatures of the cryochamber introduce a risk of frostbite. For example, during the 2019 National Football League preseason, Antonio Brown (perhaps the most talented wide receiver at the time) was been held out of the Oakland (California) Raiders training practice because of frostbitten feet.
It's not unusual for athletes like Brown to use extreme cold air cryotherapy to speed recovery from strenuous exercise, boost the immune system, and reduce inflammation. Lebron James (National Basketball Association) is one of the most famous practitioners.
But cryochamber temperatures are so cold that they can freeze the skin right off your body.
For Antonio Brown, that's exactly what happened.
There are only three important variables that govern the effectiveness of heat extraction during cryotherapy. They are:
Skin Exposure. How much skin is in contact with the cold media?
Thermal conductivity. How fast does the cold media absorb body heat?
Temperature gradient. How cold is the media?
Both cold air and cold water can expose almost the entire body. While it's typical in a cryochamber to cover the ears, hands, and feet, in an ice bath the head remains out of the water -- except perhaps for a brief dunk. So cryochamber and ice bath expose about the same amount of skin to the cold.
However, the two media differ in their thermal conductivity. The fastest method of heat extraction is solid ice in direct contact with the skin. Second fastest is cold water, followed by cold air. That means that for cold air to extract the same amount of heat in the same time as an ice bath, the temperature gradient in a cryochamber has to be much, much larger.
That's why cryochambers go down as low as -180F. They use liquid nitrogen to create temperatures that are so cold, they can freeze the water inside your skin cells, causing these cells to die, the skin to blister, and slough off from the body. That's what frostbite is -- the water inside the cells of your body freezing to ice.
And I think that's a problem.
When in the cryochamber, mittens, thick socks or booties, a head band, mask, and googles are supposed to protect the hands, feet, ears, nose, eyes, and lips from frostbite, but Antonio Brown wasn't wearing his booties, and that's how he froze the soles of his feet right off. While I admire Brown for what must be an incredible tolerance for pain, I'm not impressed with his results. Injury is the opposite of recovery.
One of the reasons I prefer the ice bath to the cryochamber is because the temperature of the water in Morozko Forge never falls below 32°F (0°C). Although it's hypothetically possible to reduce the freezing point of water to colder that 32°F by adding large quantities of salt, there's no reason to set the thermostat of the Morozko below freezing, so you won't risk frostbite in a Morozko..
Only cryochambers and sub-freezing ice packs, can give you frostbite. In this way, the ice bath is safer.
Keeping clean during cryotherapy
So why do cryotherapy centers use $100,000 liquid nitrogen machines instead of a $20,000 Morozko Forge?
There are two reasons:
Some people don't like get wet, and
Cold air is perceived as more sanitary than cold water.
The notorious reputation of hot tubs as cesspools of pathogenic soup has contributed so much to the stigma of sharing a bath with strangers that wellness centers probably offer cryochambers rather than ice baths to create the impression of safety. That's why all Morozko come equipped with water treatment systems that use microfiltration and ozone disinfection to keep the water safe and crystal-clear.
Grounding
As I wrote in Grounding Therapy, one of the most important (and overlooked) aspects of health is maintaining an electrical connection to the ground. Without grounding, static electricity charges build up throughout the body that cause ill health effects. For example, in the absence of grounding red blood cells are more prone to coagulation -- increasing the risk of dangerous blood clots that cause heart attacks and stroke. On the other hand, when grounded blood viscosity is reduced and it flows throughout the body more freely. So an important benefit of grounding is improved blood flow.
Grounding reduces inflammation and pain, promotes wound healing, improves sleep, and increases heart rate variability (Oschman et al. 2015). When two medical doctors in San Diego CA studied the effects of grounding therapy on cortisol in twelve human subjects reporting sleep disorders, they found that six weeks using grounding bedsheets normalized the diurnal cycle (Ghaly & Teplitz 2004).
Cryochambers are not grounded, but ice baths and cold plunges can be.
Most ice bath and cold plunge manufacturers don't bother with grounding, but Morozko does. In How Grounded Is Your Ice Bath? I explained how in a Morozko ice bath, the water is in electrical connection with the metal tub. The tub is in connection with copper cooling coils. The coils are in connection with the compressor that drives refrigerant flow, and the compressor is grounded thru the 3-prong power cord that plugs in to your house electrical system. The result is an instantaneous balancing of electrical charge upon immersion into the cold, grounded waters of the Morozko.
While the best grounding therapy is still the ocean, Morozko is probably the second best thing to Nature.
Halotherapy
The Greek word "halo" means a radiant aura of light surrounding the head, but when used as a prefix in biology it means of or pertaining to salt. Thus, halotherapy is salt therapy. It typically means breathing in micronized salt particles suspended in the air, although the term halotherapy can also be applied more broadly to any therapy using salt or brine to improve health (Sandu et al. 2009).
To date, commercial cryochambers have not incorporated halotherapy, although there are separate devices that atomize salt blocks within a closed booth to mimic the experience of visiting a salt cave or salt mine. Moreover, few commercial ice baths are designed to be salt tolerant. For example, in the case of a cold plunge that uses a chiller with an aluminum heat exchanger, the additional of salt to the water can create chemical interactions with the aluminum that accelerate corrosion of heat exchanger metal. The result will be a failed chiller.
Morozko does not use aluminum. All the metal parts in contact with the water are made from stainless steel, which is more durable. Thus, Morozko is warrantied for the use of Epsom and other sulfate salts. I listed the reasons for adding sulfate salts, with a recipe of how much to add, in my article Epsom Salt Makes Ice Baths Better, where I also explained why you should never use chloride salts in a Morozko.
Which brings us to the last important difference between cryochambers and ice baths when practicing cryotherapy.
An Espom salt ice bath stacks grounding therapy with cold therapy for more complete benefits.
Cryochambers don't do that.
References
Chevalier G, Sinatra ST, Oschman JL, Sokal K, Sokal P. Earthing: health implications of reconnecting the human body to the Earth′ s surface electrons. Journal of environmental and public health. 2012;2012(1):291541.
Ghaly M, Teplitz D. The biologic effects of grounding the human body during sleep as measured by cortisol levels and subjective reporting of sleep, pain, and stress. Journal of Alternative & Complementary Medicine. 2004 Nov 1;10(5):767-76.
Oschman JL, Chevalier G, Brown R. The effects of grounding (earthing) on inflammation, the immune response, wound healing, and prevention and treatment of chronic inflammatory and autoimmune diseases. Journal of inflammation research. 2015 Mar 24:83-96.
Sandu I, Alexianu M, Curcă RG, Weller O, Pascu C. Halotherapy: from ethnoscience to scientific explanations. Environmental Engineering and Management Journal. 2009 Nov 1;8(6):1331-8.
About the Author
Thomas P Seager, PhD is an Associate Professor in the School of Sustainable Engineering at Arizona State University. Seager co-founded the Morozko Forge ice bath company and is an expert in the use of ice baths for building metabolic and psychological resilience.
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