Sitting in a hot sauna raises your heart rate and widens your blood vessels, a bit like light exercise. The strongest data come from long-running Finnish studies, so treat the findings as promising, not proven.
Early evidenceA traditional Finnish sauna is 80–100 °C with low humidity. In 10–20 minutes your skin temperature climbs to about 40 °C and your core rises by around 1 °C.
To dump heat, your blood vessels widen and your heart speeds up to 100–150 beats per minute, pumping much more blood to the skin. That's similar to the heart's response to brisk walking or light jogging. Afterwards, blood pressure drops below where it started for a while.
Heat also triggers heat shock proteins, which help other proteins keep their shape and protect cells from damage. Regular sessions may improve the flexibility of your arteries over time.
Illustration of typical changes at about 80 °C. Heart rate climbs like it does during brisk walking, and blood pressure dips after you leave.
Skin heats up quickly; core temperature rises by about 1 °C.
To 100–150 bpm, like moderate exercise, to carry heat to the skin.
Blood flows to the skin; blood pressure falls after the session.
Heat shock proteins rise and help cells repair damaged proteins.
Categories from the Finnish Kuopio study (Laukkanen 2015).
2,315 Finnish men, 20 years
Compared with once a week, 2–3 sessions meant 24% lower death risk and 4–7 sessions meant 40% lower. Sessions over 19 minutes were linked to lower sudden cardiac death than sessions under 11.
Find on PubMed ↗2,315 Finnish men
4–7 sessions a week was linked to 66% lower risk of dementia and 65% lower risk of Alzheimer's disease.
Find on PubMed ↗1,628 Finnish adults
Frequent sauna users (4–7 times a week) had about 60% lower risk of stroke.
Find on PubMed ↗20 young sedentary adults
8 weeks of regular hot-water immersion improved artery function and lowered blood pressure.
Find on PubMed ↗Review
Evidence points to benefits for blood pressure, artery stiffness and inflammation, but it's mostly observational; randomised trials are needed.
Find on PubMed ↗If you enjoy it, sauna is a pleasant extra. It doesn't replace exercise.
5–10 minutes at 70–80 °C, building to 15–20 minutes over a few weeks.
More frequent sessions were linked to the biggest benefits.
Drink water before and after. You can lose 0.5 litres of sweat in a session.
A lukewarm shower and a few minutes' rest. Cold plunges are optional; their benefits are less clear.
Alcohol plus heat is linked to fainting, heart rhythm problems and sauna deaths.
You have unstable chest pain, a recent heart attack, severe aortic stenosis, very low blood pressure, or are pregnant.
✕ MythYou sweat out toxins.
✓ FactSweat is mostly water and salt. Your liver and kidneys handle toxins.
✕ MythSauna can replace exercise.
✓ FactIt mimics some heart effects but doesn't build muscle, bone or fitness in the same way.
✕ MythHotter and longer is always better.
✓ FactBenefits were seen at normal sauna temperatures and 15–20 minutes. Extreme heat raises risk.
Some people find it relaxing after training. Evidence for faster recovery is limited.
For people with stable heart disease it's usually well tolerated, but get your doctor's advice first.
They may help mood and alertness, but evidence for long-term health benefits is much weaker than for sauna.