What the Science Says About the Effects of Saunas and Cryotherapy

Performance athletes are always looking for the next best thing to boost recovery and edge out the competition. But sometimes, therapies with ancient roots prove to be tried and true. Two such therapies—sauna bathing and cryotherapy—have become increasingly popular in the modern age for athletes and the everyday man alike. But while there's lots of research about the effects of temp therapy on health, some evidence still remains hot and cold.

People have been using saunas and cryotherapy for centuries as a means for recovery, relaxation and therapeutic practice. Many claim the benefits in using temperature therapy include whole body detox and boosts in hormone production, immunity, and even aerobic endurance. We took the time to investigate these claims to see which are truly backed up in the literature—so you can start incorporating the legit ones into your training routine. 



Different types of saunas have similar results

Not every sauna is built the same, but they do all revolve around one critical feature—increased temperature. The most common types of saunas are the classical dry heat Finnish ones that can be found in most health clubs and spas. Another variety, the "steam room" or Turkish-style Hammam produces a very humid heat which can feel more intense than the classical dry sauna.

The infrared sauna is a relatively new type of recovery tool which uses infrared light in place of traditional heat elements to generate dry heat. This allows for the same physiological effects as traditional saunas at a much lower ambient temperatures, making it more tolerable for most people. 

Although there are several different types of saunas, they all result in the same essential physiological benefits which, believe it or not, closely mirror those we get from exercise. When we expose ourselves to high-temp environments, our bodies work overtime to cool us down. To do so, our circulation and heart rate increase, bringing more blood to the surface of the skin to increase sweat rate and lower our body temperature back to normal. In doing so, our bodies consume more oxygen in a way that mimics exercise.[1] And much like cardio exercise, this can have significant heart health benefits.

Saunas can keep you healthy and strong

Sauna use has additional health and performance benefits beyond cardiovascular ones:

• One study showed that a single sauna session could increase circulating white blood cells and reduce the chance of getting sick. This is at least in part due to increased white blood cell count.[2]
• Another study showed that regular sauna sessions increased endorphin production, making it a potential tool for athletic recovery.[3]
• A study of endurance athletes found post-training sauna sessions increased red blood cell volume.[4] This boost in red blood cells has exciting implications for athletic performance, since they're what carry oxygen to our muscles.
• Saunas can lower your fasting blood glucose, which can positively affect disease risk and longevity [5]
• They can also reduce total cholesterol & LDL (bad) cholesterol and raise HDL (good) cholesterol [2,6]
• Finally, saunas decrease hsCRP, a marker of general inflammation in the body [9] 



Cryotherapy's effects on inflammation—is the evidence there?

While the benefits of sauna bathing are clear and evidence-based, the effectiveness of cryo/cold therapy is far less understood—and often highly debated in the exercise science community. Cryotherapy refers to treatment with cold temperatures, typically with ice water baths or new-age cryo chambers that involve a small room or tank filled with super-cooled air. Many people claim cryotherapy increases recovery, boosts the immune system, and even increases testosterone production. However, when we look at the science behind these claims, it’s often colder than cryo tanks.

Studies show cold therapy does no better at lessening post-exercise inflammation than standard active recovery.[7] One study did show that using cryotherapy after intense training helps reduce creatine kinase levels post-exercise.[8] And while these results are promising, the study subjected participants to whole body cryotherapy twice a day for over a week. Not exactly a practical application for the average athlete.

The benefits of cryotherapy may lie in perceptions rather than physiology

While there isn’t a lot of objective evidence supporting cryotherapy, there is a wealth of evidence suggesting a correlation between cold therapy and athletic recovery. The majority of such research rely on participants’ perceived post-exercise pain before and after cryotherapy treatments or cold water immersion. Almost all of these studies show cryotherapy can be valuable for short term recovery from intense exercise if strictly measured by participants' perceived reduction of pain and delayed onset muscle soreness.

What we do know is that cold therapy reduces blood flow to our extremities, allowing the body to focus on keeping the internal organs warm. Because of this, your heart needs to work overtime to pump sufficient blood to your limbs. So cold therapy may indirectly improve cardiac and circulatory function. Beyond this, there aren’t many objective, physiologic changes caused by cryotherapy.

The key points on sauna therapy and cryotherapy

• Saunas can boost immunity, reduce inflammation, and improve multiple biomarkers critical to longevity.
• Athletes stand to gain even more from heat therapy, as it improves both performance and recovery.
• At a physiological level, cryotherapy does not appear to make meaningful changes to inflammation.
• Cryotherapy's benefits need to be investigated further, as they currently appear to be limited to changes in perceived post-exercise pain.
• If you want to incorporate heat therapy into your routine, opt for a 20 min sauna session.
• If you’re looking to boost recovery for a quick turnaround after a big athletic event, cryotherapy or an ice bath may be for you. 

Caution: temperature therapy might not be for everyone

While the benefits of using saunas for relaxation and recovery can be applied to almost anyone, there are some people who should exercise caution before turning up the heat:

• Pregnant women should refrain from temperature therapy without guidance. While there is some evidence that sauna bathing does not impact fetal development, you should always speak with your doctor before trying something new during pregnancy.
• Those who are under the influence of alcohol should never use a sauna or hot tub. Elevating your core temperature and increasing circulation can enhance the effects of alcohol and lead to serious cardiac problems.
• There is some evidence that sauna bathing can lead to acute male infertility. While the effects of this are short lived, best to keep this in mind if you and your partner are trying to make a little one.

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References

[1] Kukkonen-Harjula K, Oja P, Laustiola K, Vuori I, Jolkkonen J, Siitonen S, Vapaatalo H. Haemodynamic and hormonal responses to heat exposure in a Finnish sauna bath. Eur J Appl Physiol Occup Physiol. 1989;58(5):543-50.

[2] Pilch W, Pokora I, Szyguła Z, Pałka T, Pilch P, Cisoń T, Malik L, Wiecha S. Effect of a single finnish sauna session on white blood cell profile and cortisol levels in athletes and non-athletes. J Hum Kinet. 2013 Dec 31;39:127-35.

[3] Crinnion WJ. Sauna as a valuable clinical tool for cardiovascular, autoimmune, toxicant- induced and other chronic health problems. Altern Med Rev. 2011 Sep;16(3):215-25.

[4] Scoon GS, Hopkins WG, Mayhew S, Cotter JD. Effect of post-exercise sauna bathing on the endurance performance of competitive male runners. J Sci Med Sport. 2007 Aug;10(4):259-62. 

[5] Imamura M, Biro S, Kihara T, Yoshifuku S, Takasaki K, Otsuji Y, Minagoe S, Toyama Y, Tei C. Repeated thermal therapy improves impaired vascular endothelial function in patients with coronary risk factors. J Am Coll Cardiol. 2001 Oct;38(4):1083-8.

[6] W. Pilch, Z. Szyguła, A. Tyka et al. Effect of 30-minute sauna sessions on lipid profile in young women, Medicina Sportiva, vol. 18, no. 4, pp. 165–171, 2014.

[7] Peake JM, Roberts LA, Figueiredo VC, Egner I, Krog S, Aas SN, Suzuki K, Markworth JF, Coombes JS, Cameron-Smith D, Raastad T. The effects of cold water immersion and active recovery on inflammation and cell stress responses in human skeletal muscle after resistance exercise. J Physiol. 2017 Feb 1;595(3):695-711

[8] Wozniak A, Mila-Kierzenkowska C, Szpinda M, Chwalbinska-Moneta J, Augustynska B, Jurecka A. Whole-body cryostimulation and oxidative stress in rowers: The preliminary results. Arch Med Sci 2013; 9: 303-308

[9] Laukkanen JA, Laukkanen T. Sauna bathing and systemic inflammation. Eur J Epidemiol. 2018 Mar;33(3):351-353.