All these strategies are encompassed within what experts call "thermalism", those applications that suppose a modification of body temperature by means of external agents and whose purpose is to improve the well-being and health of those who use it.

The strategies of "thermalism" encompass modifications towards cold, placing water at temperatures below 15ºC or cryotherapy rooms known as cryochambers. On the contrary, warm modifications of temperature involve exposure to heat in saunas or hot water baths above 38ºC.

The benefits of applying the different orientations vary greatly and should be well known, both for their positive effects and for their contraindications.

If what we are looking for is an improvement in subjective perception, mood, and the ability to fall asleep, many studies back the use of cold strategies to achieve a positive effect (Cain et al. 2025). The application of cold has had much controversy in its development and has shown that it has to be done under certain standards. Specifically, the application that science demonstrates as correct is based on immersion in cold water between 15ºC and 25ºC, with a duration of at least 8 minutes; below 12-15ºC only adverse effects are found (Machado et al. 2016).

The most frequent discussion against the use of water is the inhibition of muscle adaptation pathways that prevent the proliferation of satellite cells (Piñero et al 2024; Roberts et al 2015), which goes against training adaptations.

In addition, another of the current currents points out advantages for cold exposure in improving the immune system; in this aspect there are schools such as those of the Wim Hof method that promote the deliberate use of cold water immersion to improve defenses.

On the other hand, exposure to heat has an ancestral origin, is practiced in multiple cultures, and its main benefits involve positive cardiovascular adaptations. The greatest researchers are Finnish, where its practice goes from the strictly methodological to the social. These authors point out that its practice is associated with a decrease in cardiovascular mortality, a reduction in the risk of dementias and cerebrovascular diseases, and a reduction in mortality from any cause (Laukkanen et al., 2015; Laukkanen et al., 2017; Laukkanen et al., 2018).

In addition, at the sports performance level, it simulates the cardiac effort of a brisk walk, equivalent approximately to a load of 60–100 watts, and releases heat shock proteins (HSP), therefore it is going to help in post-exercise recovery (Ketelhut & Ketelhut, 2019; Méline et al., 2021). In relation to maximum oxygen consumption and cardiovascular parameters, it shows an increase in performance compared to not using it of around an 8% improvement (Kirby et al 2021).

Multiple protocols exist, but one of the most evidenced involves exposing oneself for at least 20-30 minutes to about 85-100ºC with low humidity and repeating it 3 times per week (Kirby et al 2021).

As adverse effects or contraindications beyond the strictly medical ones that you must consult with your physician and that prevent the practice in an absolute way (for example, recent cardiac problems, severe hypotension, acute infection, fever, or pregnancy). What must be controlled in the use of the sauna is hydration, which must be continuous and adapted to the exposure time.

Finally, a method that is halfway between both applications is the use of contrasts. The application of heat and then cold (in that sequence) according to the Søeberg principle is going to improve the stimulation of brown fat and thermogenesis (Søeberg et al. 2021).

The ideal protocol involves exposing oneself longer to heat in a ratio of 2:1 or 3:1, about 3-4 times with application of immersion in water with temperatures of 38ºC for heat and between 10-15ºC for cold (Higgins et al. 2017).

The use of contrasts supposes a gym for your circulatory system, which has to deal with the vasodilation produced by heat that produces expansion to quickly adapt to the vasoconstriction produced by cold.

Conclusions

As a summary, the use of thermalism involves knowing the principles on which each strategy acts and knowing how to choose based on the objectives the one that comes closest to your needs:

If your objective involves an improvement in sports performance, as a passive ergogenic strategy, the use of the sauna is the most recommended due to its action on the cardiovascular system. In addition, it does not inhibit adaptation to training.

If your objective is the subjective improvement of the athlete's perception of recovery and soreness, the strategy is cold.

If your objective is to clear substrates produced after training and improve thermogenesis through passive impact, the use of contrasts is the most recommended method.

References

Cain T, Brinsley J, Bennett H, Nelson M, Maher C, Singh B. Effects of cold-water immersion on health and wellbeing: a systematic review and meta-analysis. PLoS ONE. 2025;20(1):e0317615.

Machado AF, Ferreira PH, Micheletti JK, de Almeida AC, Lemes ÍR, Vanderlei FM, Netto Junior J, Pastre CM. Can Water Temperature and Immersion Time Influence the Effect of Cold Water Immersion on Muscle Soreness? A Systematic Review and Meta-Analysis. Sports Med. 2016 Apr;46(4):503-14. doi: 10.1007/s40279-015-0431-7. PMID: 26581833; PMCID: PMC4802003.

Piñero, A., Burke, R., Augustin, F., Mohan, A.E., DeJesus, K., Sapuppo, M., Weisenthal, M., Coleman, M., Androulakis-Korakakis, P., Grgic, J., Swinton, P.A. and Schoenfeld, B.J. (2024), Throwing cold water on muscle growth: A systematic review with meta-analysis of the effects of postexercise cold water immersion on resistance training-induced hypertrophy. Eur J Sport Sci, 24: 177-189. https://doi.org/10.1002/ejsc.12074

Roberts LA, Raastad T, Markworth JF, Figueiredo VC, Egner IM, Shield A, et al. Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training. J Physiol. 2015;593(18):4285–301.

Laukkanen, T., Khan, H., Zaccardi, F., & Laukkanen, J. A. (2015). Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Internal Medicine, 175(4), 542–548. https://doi.org/10.1001/jamainternmed.2014.8187

Laukkanen, T., Kunutsor, S., Kauhanen, J., & Laukkanen, J. A. (2017). Sauna bathing is inversely associated with dementia and Alzheimer’s disease in middle-aged Finnish men. Age and Ageing, 46(2), 245–249. https://doi.org/10.1093/ageing/afw212

Laukkanen, T., Kunutsor, S. K., Khan, H., Willeit, P., Zaccardi, F., & Laukkanen, J. A. (2018). Sauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: A prospective cohort study. BMC Medicine, 16, 219.

Ketelhut, S., & Ketelhut, R. G. (2019). The blood pressure and heart rate during sauna bath correspond to cardiac responses during submaximal dynamic exercise. Complementary Therapies in Medicine, 44, 218–222.

Méline, T., Solsona, R., Antonietti, J.-P., Borrani, F., Candau, R., & Sanchez, A. M. (2021). Influence of post-exercise hot-water therapy on adaptations to training over 4 weeks in elite short-track speed skaters. Journal of Exercise Science & Fitness, 19(2), 134–142.

Kremers, I., Hohberger, B. & Bergua, A. Infrared thermography: different options of thermal eyelid warming. Graefes Arch Clin Exp Ophthalmol 258, 1515–1522 (2020).

Kirby, N. V., Lucas, S. J. E., Lucas, R. A. I., & Minett, G. M. (2021). Intermittent post-exercise sauna bathing improves markers of exercise capacity in hot and temperate conditions in trained middle-distance runners. European Journal of Applied Physiology, 121(2), 621–635.

Søberg, S., Löfgren, J., Philipsen, F. E., Jensen, M., Hansen, A. E., Ahrens, E., Nystrup, K. B., Nielsen, R. D., Sølling, C., Wedell-Neergaard, A.-S., Berntsen, M., Loft, A., Kjær, A., Gerhart-Hines, Z., Johannesen, H. H., Pedersen, B. K., Karstoft, K., & Scheele, C. (2021). Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men. Cell Reports Medicine, 2(10), 100408.

Higgins, T. R., Greene, D. A., & Baker, M. K. (2017). Effects of cold water immersion and contrast water therapy for recovery from team sport: A systematic review and meta-analysis. Journal of Strength and Conditioning Research, 31(5), 1443–1460.