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Last updated February 23, 2020. 6 minute read

Cold therapy or cryotherapy: claims and supporting research

There’s some evidence that cold may help inflammation and muscle soreness, but researchers disagree on whether the effect is significant. Studies do show that cold exposure can activate your immune system.

Linnea Zielinski Written by Linnea Zielinski
Reviewed by Mike Bohl, MD, MPH

How much discomfort would you ensure in the name of better health? Looking past the attractive claims to the actuals methods, a lot of wellness is, well, uncomfortable. After working eight hours at a desk each day for years, the stretch yoga provides—while perhaps helpful—isn’t the most relaxing experience. Swallowing large vitamins is tolerable at best and gag-inducing at its worst. A new trend in the health space, cold exposure therapy, can’t claim to be any different.

Temperature therapy is old medicine, really old medicine. Different cultures have used some modalities of this, such as saunas, for ages. But as technology advances, we’re able to create more extreme conditions in the name of improved health, from infrared saunas to full-body cryotherapy. It’s all too tempting to think that treatments this extreme must be doing something for you, but what does the science actually say?

Vitals

  • There are many different types of cold exposure therapy, such as cryotherapy, ice baths, and cold showers.
  • The idea is that cold is a small amount of stress that can strengthen the body over time.
  • There’s some evidence that cold may help inflammation and muscle soreness, but researchers disagree on whether the effect is significant.
  • Studies do show that cold exposure can activate your immune system.
  • People with heart conditions should not try cold exposure therapy.

What is cold exposure therapy?

There’s a wide range of different treatments that would all qualify as “cold exposure therapy,” which, at its core, is simply using cold temperatures to promote wellness. In the cold space, cryo and the Wim Hof Method are expanding their reach; the later was even featured on Netflix’s controversial new series, The Goop Lab. Where cryo surrounds your body with temperatures well below -200° Fahrenheit, the Wim Hof Method isn’t quite so extreme.

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Made popular by Wim Hof (who is also called “Iceman”), an extreme athlete known for breaking multiple records involving exposure to cold such as cold water swimming, the method aims to reduce stress through meditation, breathing exercises, and—you guessed it—cold exposure. Unlike cryotherapy (cold therapy that subjects part or all of your body to extremely cold temperatures for several minutes), which is only available in limited areas and may be prohibitively expensive for some people, cold water therapy and ice baths can be done at home. The Win Hof method suggests using your shower.

If you’ve trained as an athlete or even followed a serious training program, you may know about contrast showers (also called hot-cold showers or hydrotherapy showers), in which you oscillate between hot water and cold water to prevent delayed-onset muscle soreness, increase alertness, and maybe even boost weight loss. The Wim Hof Method doesn’t give you respite of any hot breaks. You simply subject yourself to cold water immersion by taking a freezing shower.

Benefits of cold exposure therapy

Before you race to stand under the freezing cold faucet, science is a bit torn on whether cold exposure therapy holds significant benefits. Most of the purported health benefits of cold therapy come down to the idea of hormesis. Essentially, you can think of this as the biological example of the expression, “the dose makes the poison.” The idea is that small amounts of something stressful can strengthen your body, while large amounts can be toxic or harmful. Although anecdotal, fans claim cold exposure increases well-being, which may be attributed to endorphins.

Recovery and muscle soreness

Some studies on cryotherapy suggest the treatment helps reduce inflammation (Ramos, 2016), alleviate pain (Bettoni, 2013), and speed muscle recovery (Rose, 2017). But the first of these studies was done in rats and the second on joint pain in people with fibromyalgia. It’s important to keep in mind that these results may not hold true if the studies are done in humans and with larger participant groups that are more representative of the general population. In fact, one meta-analysis of existing studies found that the results, even though they sounded great, weren’t actually significantly different from baseline (Costello, 2015). 

But there is biological thinking here. Cold water exposure causes vasoconstriction (narrowing of blood vessels), which makes your blood pool. When you emerge from the cold water, vasodilation (widening of blood vessels) occurs. Researchers believe that this process increases the rate at which oxygen is delivered to your muscles, speeding recovery time (Yeung, 2016). But the effect of ice baths and cold immersion could benefit from additional research, just like cryotherapy. The researchers who suggested the effects of cryo may not be significant also suggest additional work that’s more rigorous to see if cryotherapy can actually make a true difference in recovery and muscle soreness following a training session (Costello, 2015).

Metabolic rate

Proponents of cold exposure therapy also claim it can help you lose weight by increasing metabolism. When young, lean men were exposed to cold in one study, the calories they burnt did indeed increase, even before the onset of shivering. Energy expenditure increased at its max by 31% over baseline, and the increase lasted while they endured the cold before shivering—which was a little under 30 minutes (Acosta, 2018). 

To put that in perspective, someone who burns 2000 calories a day burns approximately 41 calories every 30 minutes. A 31% increase would result in burning about 54 calories in 30 minutes—but only if their metabolisms immediately increased by 31% (they didn’t). And as soon as they warm up, their energy expenditure is right back to normal. That would be fewer than 13 calories for 30 minutes in the cold, so it’s debatable whether this effect is significant enough to be called a health benefit. We also don’t know if these effects hold true in a more general population.

But cold exposure may also boost the conversion of white fat to metabolically-active brown fat, which fans of cold therapy point out as one of its major benefits. Brown fat is responsible for adaptive thermogenesis, a process by which energy is converted into heat to warm the body. But we know much more about how this works in mice than in humans, and there appear to be significant differences in how the same types of fat function between the species. Researchers are still trying to figure out if white fat in humans can be converted to brown fat the same way as in mice, and there are barriers. Animals in studies, for example, are exposed to cold for periods of time humans cannot withstand in order to see significant activation of these fat cells that can expend energy (Elattar, 2015).

Immunity

Wim Hof himself emphasizes that cold therapy improves immunity, and research does seem to support this idea. Cold exposure, especially when preceded by exercise in water that’s 64° F, increased counts of white blood cells and natural killer (NK) cells in one study. The researchers behind the study concluded that cold exposure has immunostimulating effects, but even more so when proceeded by the water-based exercise (Brenner, 1999). An earlier study found that repeat immersions in cold water—one hour of immersion three times a week for six weeks—did appear to activate the immune system to “a slight extent” (Janský, 1996).

Potential risks of cold exposure therapy

Even if we’re not talking about the most extreme treatments, such as cryotherapy, cold exposure therapy does have its risks. People with heart conditions should not partake in cryotherapy, cold showers, as suggested in the Wim Hof Method, or treatments that involve moving from one extreme temperature to another. Other risks include hypothermia, stress, respiratory issues, and changes in blood pressure (Elattar, 2015). Before attempting any of this on your own, you should talk to a healthcare provider. Part of the danger of these treatments is that very little research has been done on the potential side effects. The same meta-analysis that suggested the health benefits may be overstated also underscored the need to look further into potential risks associated with these therapies (Costello, 2015).