Sauna frequency, not temperature, is what moved the numbers in 2,315 men
In short
In a cohort of 2,315 middle-aged Finnish men followed for roughly 20 years, men using a sauna 4–7 times per week had 63% lower risk of sudden cardiac death, 48% lower risk of fatal coronary heart disease and 40% lower all-cause mortality than men using it once a week. Risk was also lower in those staying longer than 19 minutes per session, and the cohort's saunas averaged about 79°C. Weekly frequency, more than temperature or duration, is what separated the groups — and there is no basis for transferring those figures to infrared cabins that run far cooler.
The most-cited sauna data comes from a cohort of 2,315 middle-aged Finnish men followed for about 20 years. The variable that separated them was not the temperature, the wood, or whether the heat was infrared — it was how many times a week they went in.
How big was the difference?
Compared with once-a-week users, men going 4–7 times a week had 63% lower risk of sudden cardiac death, 48% lower fatal coronary heart disease and 40% lower all-cause mortality. The 2–3 times a week group fell in between. Time per session mattered too: risk was lower among those staying longer than 19 minutes.
Those saunas were traditional dry saunas averaging about 79°C. So the conditions behind these numbers are roughly 80°C, about 20 minutes, four or more times a week. Quote the figures without the conditions and you are describing something else.
Do the same numbers apply to infrared?
There is no basis for assuming so. Home infrared cabins typically top out near 79°C and are used well below that. Sauna blankets max out around 70°C and portable steam boxes around 65°C. Infrared heats the body directly rather than the air, so it can feel intense while delivering a different magnitude of heat stress than a traditional sauna.
What counts is the stimulus. The plausible mechanism behind the observed benefit is an acute cardiovascular load that raises heart rate to 100–150 bpm, the blood pressure drop that follows, and, with repeated exposure, plasma volume expansion and improved endothelial function. A session that barely raises heart rate does not create that stimulus.
What it means for a lifter
The useful contrast is with cold water immersion. Cold immediately after training blunts hypertrophy adaptation; heat exposure has not shown that suppression, and there is evidence pointing the other way — heat slowing muscle loss during disuse. So unlike cold, a sauna can sit in the post-lifting window at little adaptive cost.
The cost is elsewhere. Twenty minutes in a sauna can cost over half a litre in sweat, and stacking that on a body already dehydrated by training compounds the cardiovascular load. If it goes after the session, replace fluid and electrolytes first, and never combine it with alcohol.
This is an observational cohort, so it does not establish causation — healthier men going to the sauna more often cannot be fully ruled out — and the population was middle-aged Finnish men. The safety side is clearer: unstable angina, recent myocardial infarction and severe aortic stenosis are contraindications, and uncontrolled low or high blood pressure, pregnancy, or alcohol are reasons not to enter. Get out immediately if you feel dizzy or nauseated. Resistance training's own vascular effects are covered in resistance training and artery health, and the exercise dose that lowers blood pressure in exercise dose for blood pressure.
One thing to get right in your bodyweight log
Bodyweight taken after a sauna is a dehydrated number, not a lighter body. A Muscle Index score normalises the Big 3 total by a bodyweight coefficient (DOTS), so entering a dehydrated weight inflates the score. That score disappears the moment you rehydrate.
The rule is simple: weigh under identical conditions every time — on waking, fasted, before the sauna. Keep the recovery routine and the bodyweight measurement completely separate so your Muscle Index trend reflects training rather than fluid.
Frequently asked questions
How often should you use a sauna?
In a cohort of 2,315 Finnish men followed about 20 years, the lowest-risk group used a sauna 4–7 times per week. They had 63% lower risk of sudden cardiac death and 40% lower all-cause mortality than once-a-week users.
How long should a session be?
In the same cohort, risk was lower among men staying longer than 19 minutes per session, and the saunas averaged about 79°C. That makes roughly 20 minutes at about 80°C the reference condition.
Does an infrared sauna give the same benefit?
There is no basis for assuming it does. Home infrared cabins usually top out near 79°C, sauna blankets around 70°C and portable steam boxes around 65°C, and actual use is cooler still — a different magnitude of heat stress from the traditional saunas the cohort observed.
Does a sauna after training hurt muscle growth?
Unlike cold water immersion, heat exposure has not been shown to blunt hypertrophy adaptation, so a post-training sauna carries little adaptive cost. The caution is fluid: stacking it on an already dehydrated body compounds cardiovascular load, so replace fluid and electrolytes first.
Can I record bodyweight after a sauna?
No. Post-sauna bodyweight is a dehydrated value, and because the Muscle Index normalises by a bodyweight coefficient, it inflates the score. Weigh on waking, fasted, and before the sauna, under the same conditions every time.
Source: Men's Health