Sauna: what the studies show for the heart, recovery and sleep

By the Voltra team · Updated 30 September 2026

What a sauna does to your body

Pooling 16 studies, a 2020 meta-analysis found that within half an hour of a session, body temperature was up by about 0.9 °C and heart rate by about 18 beats a minute, while systolic blood pressure was down by 5.6 mmHg and diastolic by 6.5 mmHg [2]. In a small study of young men who sat three times for 15 minutes at about 91 °C, heart rate rose to about 126 beats a minute and they lost 0.72 kg, mostly as sweat [7]. That weight is water, not fat.

The Finnish studies

The best-known findings come from one Finnish cohort, the Kuopio Ischaemic Heart Disease Study. Men in eastern Finland were asked how often they used a sauna when they joined, between 1984 and 1989, and followed for decades [1]. Later analyses of the same cohort looked at high blood pressure and stroke [8] [9].

Percentages calculated from the adjusted hazard ratios [1] [8] [9].

These are links, not proof. Sauna habits were asked about once, at the start [1]; only 201 of the 2,315 men, about 9% (calculated), used a sauna 4 to 7 times a week, and 10 of them died suddenly of heart disease [1]. Men who use a sauna often may differ in other ways, and letters to the journal argued the link may not be causal [10]. The researchers did adjust for many factors, including fitness and socioeconomic status in the blood pressure study and physical activity and socioeconomic status in the stroke study, and the links held [8] [9]. Only the stroke study included women [9].

Trials on blood pressure and the heart

In a 2022 trial, 47 inactive adults with at least one heart risk factor, only 6 of them men (calculated), were randomised to exercise three times a week, the same exercise followed by 15 minutes in a sauna, or neither, for 8 weeks. The sauna started at 65 °C and rose by 5 °C every two weeks. Compared with exercise alone, adding the sauna lowered systolic blood pressure by a further 8.0 mmHg, raised fitness a little more and lowered total cholesterol [3].

In a 2023 trial, 41 adults with stable coronary artery disease used a sauna at 79 °C four times a week for 8 weeks. Their blood pressure and blood-vessel function changed no more than in a control group who carried on as usual [11].

Recovery and muscle

Does heat after training help you recover? A 2025 systematic review of 14 studies with 194 people found that four showed no effect on recovery of performance, four a benefit and one harm; longer programmes may help running in the heat, but repeated heat didn't improve cycling performance or VO2max [4]. Its conclusion: "it is not possible to draw definitive conclusions about the effects of post-exercise heat exposure on recovery and physical performance development" [4]. A 2025 meta-analysis of 10 studies found only a trivial effect on endurance performance in the heat, with low to very low certainty [5].

Single sessions can make you feel better. In 16 male basketball players, 20 minutes in an infrared sauna at about 43 °C after a strength session eased muscle soreness and lessened the drop in jump height the next morning, compared with resting [12].

It hasn't added muscle. In 40 female athletes on a 6-week strength and power programme, 10 minutes in an infrared sauna at 50 °C after training three times a week didn't change muscle growth, which was similar with or without it [13]. In 14 older adults, 8 weeks of infrared sauna, 45 minutes at about 60 °C three times a week, built no muscle, didn't raise leg strength and didn't change muscle protein building, though the study had no control group [14].

The growth hormone claim goes back to a 1986 study: in 10 men who sat in an 80 °C sauna for an hour, twice a day for a week, growth hormone rose 16-fold, but the rise faded after the third day and muscle wasn't measured [15]. Two of the trials above were part-funded by Harvia, which makes saunas, and two of the studies by the Finnish Sauna Society [4] [12] [13] [16].

Sleep

Many regular users say a sauna helps them sleep: in an online survey of 482 of them, 83.5% reported sleep benefits [17]. Surveys like that can't show cause, and the only trial we found that measured sleep, in the 16 basketball players above, saw no difference in how long or how well they slept after the sauna [12].

Warm water has better evidence. A 2019 meta-analysis found that a warm shower or bath at 40 to 42.5 °C, taken 1 to 2 hours before bed, for as little as 10 minutes, helped people fall asleep faster and improved how they rated their sleep [18]. That was baths and showers, not saunas. For how much sleep you need, see our sleep guide.

Sauna or steam room

A sauna is dry heat; a steam room is cooler but humid [7]. Kuwait's health ministry caps a sauna at 65 to 90 °C and a steam room at 40 to 50 °C in health institutes, which it defines as places offering exercise equipment, pools or jacuzzis alongside steam rooms, saunas and oriental baths [19].

Humid heat is harder on the body than the lower temperature suggests. When 10 young men compared a dry sauna at about 91 °C with a humid one at 59 °C, the humid session raised their core temperature more (1.61 against 1.16 °C) and their heart rate higher (to about 138 against 126 beats a minute), though they lost only half as much weight in sweat; the authors judged the humid sauna the more stressful [7]. Sweat can't evaporate well in humid air [7].

The rules in Kuwait and Saudi Arabia

Kuwait Ministry of Health, 2025 health requirements for health institutes [19].

Kuwait's limits apply according to the type of unit and the maker's recommendations, taking account of how long people stay inside, and saunas must be well ventilated and cleaned regularly [19]. In Saudi Arabia, the municipal ministry's requirements for relaxation and body-care centres say the temperature in the bath must be kept suitable to avoid heat shock, and customers must sign that they're free of chronic conditions such as asthma, high blood pressure, heart disease, epilepsy and skin conditions [20]. We found no published sauna rules from the UAE or Qatar.

Who should be careful

• Straight after hard exercise. Saudi Arabia's health ministry advises against a hot bath or steam room right after exercise: blood vessels are already widened, and the heat widens them further, which can drop your blood pressure, especially if you've lost fluid. It advises replacing lost fluids before going into a sauna [6].
• With alcohol. In Finland, deaths in saunas were rare, fewer than 2 a year per 100,000 people, but half of those who died were under the influence of alcohol [21]. A review warns that alcohol in the sauna raises the risk of low blood pressure, abnormal heart rhythm and sudden death [22].
• Heart conditions. The same review lists unstable angina, a recent heart attack and severe aortic stenosis as reasons not to use a sauna, while judging it safe for most people with stable heart disease [22]. Ask your doctor first.
• Pregnancy. A raised body temperature early in pregnancy has been linked with neural tube defects, about double the risk in a meta-analysis of 15 studies [23]. For saunas alone the data are too thin to be sure [24]. Saudi Arabia's health ministry advises pregnant women to avoid exercising in hot or humid weather so their body temperature doesn't rise [6]. Talk to your doctor before using a sauna when pregnant.
• Men trying for a baby. In 10 men who used a sauna at 80 to 90 °C for 15 minutes twice a week for three months, sperm count and movement fell sharply; both were back to normal six months after they stopped [25].

For the signs of heat exhaustion and heat stroke, see our guide to exercising in the heat. If you plan to follow the sauna with a cold plunge, read our ice bath guide on the cold-shock risks.

In Voltra

For muscle, the trials above point back to training rather than heat. Voltra sets a daily calorie target and a protein target for you, and our protein guide explains how much protein you need. The Coach answers questions using what you've logged.

Frequently asked

Sources

1. Laukkanen T, Khan H, Zaccardi F, Laukkanen JA (2015). Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Intern Med 175(4):542–8. Abstract. 2,315 men in eastern Finland (Kuopio Ischaemic Heart Disease Study).
2. Li Z, Jiang W, Chen Y, et al. (2020). Acute and short-term efficacy of sauna treatment on cardiovascular function: a meta-analysis. Eur J Cardiovasc Nurs 20(2):96–105. Abstract. 16 studies.
3. Lee E, Kolunsarka I, Kostensalo J, et al. (2022). Effects of regular sauna bathing in conjunction with exercise on cardiovascular function: a multi-arm, randomized controlled trial. Am J Physiol Regul Integr Comp Physiol 323(3):R289–R299. Abstract and methods. 47 adults, 8 weeks.
4. Ahokas EK, Hennessy RS, Hanstock HG, Kyröläinen H, Ihalainen JK (2025). Effects of post-exercise heat exposure on acute recovery and training-induced performance adaptations: a systematic review. Sports Med Open 11(1):106. Abstract and funding statement: supported in part by the Finnish Sauna Society.
5. Solomon TPJ, Laye MJ (2025). The effect of post-exercise heat exposure (passive heat acclimation) on endurance exercise performance: a systematic review and meta-analysis. BMC Sports Sci Med Rehabil 17(1):4. Abstract. 10 studies, 199 people.
6. وزارة الصحة، المملكة العربية السعودية (١٤٤١ هـ / ٢٠٢٠). دليل النشاط البدني للممارس الصحي. In Arabic. Printed pp. 19 and 22, read from the page images.
7. Pilch W, Szygula Z, Palka T, et al. (2014). Comparison of physiological reactions and physiological strain in healthy men under heat stress in dry and steam heat saunas. Biol Sport 31(2):145–9. Abstract and methods. 10 men.
8. Zaccardi F, Laukkanen T, Willeit P, Kunutsor SK, Kauhanen J, Laukkanen JA (2017). Sauna bathing and incident hypertension: a prospective cohort study. Am J Hypertens 30(11):1120–1125. Abstract. Same Finnish cohort.
9. Kunutsor SK, Khan H, Zaccardi F, Laukkanen T, Willeit P, Laukkanen JA (2018). Sauna bathing reduces the risk of stroke in Finnish men and women: a prospective cohort study. Neurology 90(22):e1937–e1944. Abstract. Same Finnish cohort.
10. Kivimäki M, Virtanen M, Ferrie JE (2015). The link between sauna bathing and mortality may be noncausal (letter). JAMA Intern Med 175(10):1718. Letter; title only (no abstract). A second letter with the same title, by Epstein and Shoenfeld, appeared alongside it.
11. Debray A, Gravel H, Garceau L, et al. (2023). Finnish sauna bathing and vascular health of adults with coronary artery disease: a randomized controlled trial. J Appl Physiol 135(4):795–804. Abstract. 41 adults with coronary artery disease.
12. Ahokas EK, Ihalainen JK, Hanstock HG, Savolainen E, Kyröläinen H (2023). A post-exercise infrared sauna session improves recovery of neuromuscular performance and muscle soreness after resistance exercise training. Biol Sport 40(3):681–689. Abstract, results and acknowledgements: supported in part by Harvia Oyj.
13. Ahokas EK, Hanstock HG, Kyröläinen H, Ihalainen JK (2025). Effects of repeated use of post-exercise infrared sauna on neuromuscular performance and muscle hypertrophy. Front Sports Act Living 7:1462901. Abstract and funding statement: supported in part by Harvia Oyj and the Finnish Sauna Society.
14. Fuchs CJ, Betz MW, Petrick HL, et al. (2025). Repeated passive heat treatment increases muscle tissue capillarization, but does not affect postprandial muscle protein synthesis rates in healthy older adults. J Physiol 603(1):167–186. Abstract. 14 older adults, no control group.
15. Leppäluoto J, Huttunen P, Hirvonen J, Väänänen A, Tuominen M, Vuori J (1986). Endocrine effects of repeated sauna bathing. Acta Physiol Scand 128(3):467–70. Abstract.
16. Harvia Plc. Harvia: shaping the global sauna market (company website). What the company makes.
17. Hussain JN, Greaves RF, Cohen MM (2019). A hot topic for health: results of the Global Sauna Survey. Complement Ther Med 44:223–234. Abstract. Online survey of 482 regular sauna users.
18. Haghayegh S, Khoshnevis S, Smolensky MH, Diller KR, Castriotta RJ (2019). Before-bedtime passive body heating by warm shower or bath to improve sleep: a systematic review and meta-analysis. Sleep Med Rev 46:124–135. Abstract. Warm baths and showers, not saunas.
19. وزارة الصحة، دولة الكويت (اللجنة المشتركة للرقابة على الصالونات والمعاهد الصحية) (٢٠٢٥). دليل الاشتراطات الصحية للمعاهد الصحية والصالونات ومراكز التجميل والعناية الشخصية. In Arabic. Section 2, health institutes (gyms), PDF p. 13 (printed 12/16), read from the page image.
20. وزارة الشؤون البلدية والقروية والإسكان، المملكة العربية السعودية (١٤٤٣ هـ / ٢٠٢٢). اشتراطات مراكز الاسترخاء والعناية بالجسم. In Arabic. PDF pp. 6 and 14, read from the page images.
21. Kenttämies A, Karkola K (2008). Death in sauna. J Forensic Sci 53(3):724–9. Abstract. Deaths in saunas in Finland, 1990–2002.
22. Hannuksela ML, Ellahham S (2001). Benefits and risks of sauna bathing. Am J Med 110(2):118–26. Abstract. Narrative review.
23. Moretti ME, Bar-Oz B, Fried S, Koren G (2005). Maternal hyperthermia and the risk for neural tube defects in offspring: systematic review and meta-analysis. Epidemiology 16(2):216–9. Abstract. 15 studies.
24. Milunsky A, Ulcickas M, Rothman KJ, Willett W, Jick SS, Jick H (1992). Maternal heat exposure and neural tube defects. JAMA 268(7):882–5. Abstract. 23,491 women.
25. Garolla A, Torino M, Sartini B, et al. (2013). Seminal and molecular evidence that sauna exposure affects human spermatogenesis. Hum Reprod 28(4):877–85. Abstract. 10 men.

Sources checked on 30 September 2026.

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