It’s very likely that when you read the word “sauna,” your mind immediately goes to “relaxation.” And while it’s true that the sauna is an incredible tool for unwinding, that’s only about 10% of what actually happens inside the body when we expose ourselves to heat.
Heat exposure triggers a series of physiological responses involving the cardiovascular, muscular, nervous, hormonal, and respiratory systems.
The amount of deep benefits this tool provides is truly fascinating. And in this article, we’re going to explore them system by system.
Cardiovascular System: the heart works harder (and that’s a good thing)
As soon as we step into the sauna, the feeling is usually: “wow, this feels amazing.” The muscles relax, the mind slows down, and we enter a deep state of relaxation.
Now, after about 10 or 15 minutes (depending on the person and the temperature), a different sensation appears: the heart starts beating faster and the body begins to feel challenged. Discomfort begins (which is exactly what we’re looking for in order to create adaptations).
Here’s what’s happening: when the body’s core temperature starts to rise, the body tries to cool itself down. How? Blood vessels expand to bring hot blood toward the skin and release heat. And this forces the heart to work harder.
As a result, blood flow increases, the volume of circulating blood rises, and the heart pumps faster to sustain this process. During a sauna session, heart rate can reach between 100 and 150 BPM, similar to what happens during moderate aerobic exercise.
This cardiovascular “training effect” has very positive impacts on heart health. In fact, a study published in 2018 (Laukkanen, T., et al.) found that frequent sauna use is associated with lower cardiovascular mortality.
And all of this without moving a single muscle. Pretty impressive, right?
Sweating
Another way the body regulates temperature is through sweating.
The primary function of sweat is thermoregulation: cooling the body as sweat evaporates from the skin, helping prevent overheating during heat exposure or physical exercise.
But beyond temperature regulation, sweating may also support the body’s natural detoxification processes.
Although the liver and kidneys are primarily responsible for eliminating toxins, different studies suggest that sweat may help remove small amounts of heavy metals and certain chemical compounds.
This is a very interesting study in which researchers evaluated 69 police officers from the Utah Meth Cops Project who experienced chronic symptoms after years of occupational exposure to chemicals related to methamphetamine laboratories.
What did they find? That sauna use combined with nutritional therapy may help relieve chronic symptoms that appear after exposure to chemical substances associated with methamphetamine-related police activities.
Muscles
As we’ve seen, the heat from the sauna causes vasodilation and increased blood circulation in order to lower our core temperature. This mechanism directly impacts the muscles:
-
More oxygen reaches the muscles. Oxygen is essential for muscle cells to produce the energy needed for movement.
-
Heat helps relax muscles, reduce pain and stiffness, and improve flexibility.
In this sense, the sauna is a powerful tool for recovery and muscle pain relief. It may also help support muscle growth…
Hormones and Neurotransmitters
Growth Hormone
Growth hormone is essential for cellular regeneration, growth, metabolism, muscle recovery, and bone health.
In children, it is crucial for height increase and bone development. In adults, it helps maintain muscle mass, bone density, and regulate blood sugar.
Deliberate heat exposure (through sauna use) can significantly increase levels of this hormone, helping with muscle recovery, muscle growth, and tissue repair.
However, increasing this hormone does require a specific sauna protocol: research suggests that performing two 20-minute sessions at 80 °C, separated by a 30-minute cooling period, may generate a significant increase in growth hormone levels.
Endorphins and Dynorphins
Andrew Huberman explains that when we enter a sauna, the body releases dynorphins: molecules associated with discomfort and acute stress. And while this may sound negative, it actually triggers a very beneficial response.
The release of dynorphins also leads to the release of endorphins, commonly known as the “feel-good hormones.” They are responsible for the sense of calm and happiness many people experience after a sauna session.
Over time, the release of dynorphins creates changes in the efficiency of endorphins. Put simply: people experience an increase in their “baseline mood” and become more capable of responding positively to life events.
In other words: small doses of discomfort can train the brain to feel better.
Heat Shock Proteins: the body’s cellular protection mechanism
Heat shock proteins (HSPs) are a family of stress-induced proteins that act as cellular “protectors.”
Their primary role is helping repair damaged proteins and preventing them from becoming deformed or “misfolded” under stress conditions such as extreme heat.
Proteins folding incorrectly? What are you talking about?
Huberman explains it this way: heat alters protein quality and the way proteins are configured at the molecular level. Misfolded proteins are associated with neurodegenerative diseases such as Alzheimer’s and Parkinson’s.
So when cells are exposed to environmental stressors (like extreme heat), HSPs appear to protect proteins from harmful changes that stress/heat may cause.
In this sense, sauna use is a powerful tool for promoting health, resilience, and longevity.
Respiratory System
The heat and humidity of the sauna also create positive effects on the respiratory system.
When we inhale hot air, the airways tend to relax and open, which may make breathing easier and provide temporary relief for people with conditions such as asthma or chronic obstructive pulmonary disease (COPD).
Additionally, some studies suggest that regular heat exposure may stimulate certain immune responses, helping the body defend itself more effectively against respiratory infections.
Beyond that, many people report an immediate sensation of deeper and more relaxed breathing after a session.
Conclusion: much more than relaxation
A sauna is far more than just a relaxing experience.
Sauna use improves circulation, strengthens the cardiovascular system, stimulates hormones and proteins associated with recovery and longevity, promotes mental relaxation, and may support respiratory and immune health.
And perhaps the most interesting part is this: the body adapts, recovers, and becomes stronger precisely because it goes through a small, controlled dose of discomfort.
Research
Sears ME, Kerr KJ, Bray RI. (2012). Arsenic, cadmium, lead, and mercury in sweat: a systematic review. J Environ Public Health. Link
Ross HG and Sternquist CM. (2011). Methamphetamine exposure and chronic illness in police officers: significant improvement with sauna-based detoxification therapy. Toxicology and Industrial Health. Link
Laukkanen T. et al. (2018). Sauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: a prospective cohort study. BMC Med 16, 219. Link
Leppäluoto J, Tapanainen P, Knip M. (1987). Heat exposure elevates plasma immunoreactive growth hormone-releasing hormone levels in man. J Clin Endocrinol Metab. Link
Hu C, Yang J, Qi Z, Wu H, Wang B, Zou F, Mei H, Liu J, Wang W, Liu Q. (2020). Heat shock proteins: Biological functions, pathological roles, and therapeutic opportunities. MedComm. Link
Chaudhuri TK, Paul S. (2006). Protein-misfolding diseases and chaperone-based therapeutic approaches. FEBS J. Link
Kirby, N.V., Lucas, S.J.E., Armstrong, O.J. et al. (2021). Intermittent post-exercise sauna bathing improves markers of exercise capacity in hot and temperate conditions in trained middle-distance runners. Eur J Appl Physiol 121, 621–635. Link
Cox NJ, Oostendorp GM, Folgering HT, van Herwaarden CL. (1989). Sauna to transiently improve pulmonary function in patients with obstructive lung disease. Arch Phys Med Rehabil. Link
