Athletes already know the answer from years of cultural knowledge, research, and firsthand experience. No, it doesn't make your cardio fitness meaningfully better. If you did sauna training for years and then tried to ramp up for a marathon, you'd be hopelessly out of shape.

Endurance athletes obsessively track VO2 max, basically your body's ability to consume oxygen during workouts, and it certainly doesn't improve with sauna training.

It's like asking "if you only did puzzles, would you be smarter?" Well, in a way, yes, but if you actually want to compete with someone with a good education you have to read.

Same with physical exercise. It puts a lot of different stresses on your body that saunas don't. The question isn't "do saunas make you physically fit," because they don't. The question is "for people who don't want to exercise, does sauna training alone meaningfully extend your healthspan?" I'm guessing the answer is "a little but not enough," but I'm not sure.

Moreover, I'm from a very hot and humid tropical region. Its normal to ne 40°C with 80% humidity there. And you dont see people having better health or longevity (Yucatan peninsula) .

Cardiac hypertrophy is not necessarily a bad thing, it can be the result of positive adaptation, such as exercising.

Eccentric hypertrophy (athlete's heart) is the positive adaptation resulting from training the heart. The heart has a lower resting rate and is more efficient at pumping blood. It returns to normal size if training stops.

You'll never reach a state of hypertrophic cardiomyopathy (the bad kind of hypertrophy) with exercise. Its cause is usually genetic.

Not true. You can't really train your muscles to use less oxygen for the same energy output (what "oxygen-efficiency" would imply). You rather increase their capacity to take up oxygen from the blood and burn it. They will use more oxygen to output more energy.

That additional oxygen needs to come from somewhere. Endurance training at the same time trains the heart to deliver more oxygen to the periphery; the primary mechanism is increased cardiac stroke volume.

This is terribly uniformed. Do not listen to this.

Cardiac hypertrophy isn't a "bad thing". This is completely contextual. What you don't want, for example, is pathological hypertrophy from things like hypertension, or exclusive left ventricular hypertrophy without associated increase in chamber size.

The heart is very complex. You 100% should exercise it.

Wikipedia says Athlete's heart is benign: https://en.wikipedia.org/wiki/Athletic_heart_syndrome

This is why I hate health science. Informed people can have the same information and come to opposite conclusions. The entire field is made up of contradictory explanations and principles, to the extent that it’s unknowable what’s true or not.

That seems… misguided.

Sources?

Your heart is also a muscle.

Much of it is, sure, but certainly not all of it! On your comparison to Sweden, be cautious! Finns generally have a higher risk and incidence of cardiovascular disease compared to native Swedes - in fact, they have some of the highest risk in the world!

Research from Earric Lee and/or Jari Laukkanen from this past decade will have clinical trials with controlled groups rather than just long-term population tracking. There are within-Finland studies comparing high-risk Finns who use the sauna 4 to 7 times a week against high-risk Finns who use it only once a week, showing a clear effect (https://pubmed.ncbi.nlm.nih.gov/25705824/). Here is a non-randomized experiment showing a dose-response (https://pubmed.ncbi.nlm.nih.gov/29048215/).

Those are just indications of information available. I would also argue that while of course randomized experiments are ideal, it is a mistake to dismiss all other forms of evidence so readily, especially with such preponderance of it.

30 seconds? What kind of torture room of a sauna are you going in?

IMHO. 10-20 mins is good enough. I wouldn't try to stay for an hour.

If 10mins feels too much, do less.

lol, this is true. Wish I could tolerate it longer like a proper Finn. I’ll go 25 mins occasionally but mostly I do 15 mins, break, another 5-10 mins..

You're saying that crime leads to longevity? Big if true.

Thank you for the resources.

I do wonder what the correlation is: is it only because of excercise, or at least partially also due to the fact those who can set aside time and effort (and often, money) to exercise, have a "better" life than those who don't?

For example, high life expectancy in Madrid, and Switzerland are often attributed to having broad access to great healthcare and stress-free lifestyle(both), despite living a relatively "unhealthy" lifestyle, at least in Madrid. Eating fried food everyday, little exercize among elderly (at least if you don't count walking to the bar). Those 85 year+ Madrileños probably had their last formal exercise when they had to do their military service back in the day.

As in the case of top athletes, in your second article, is their longevity due to heavy exercise, or kind of, "despite it", and at least partially due to their accumulated wealth, health-conscious mindset plus the ability to afford a stress-free life?

Japan has a +4 years lead of life expectancy over Finland; Norway almost +3 years on Finland. I am not saying this is conclusive per se, but to me the sauna-people-live-forever is not backed up by the data. I would instead reason that, e. g. weight correlates a lot more here.

>which have beneficial effects on muscle growth and repair?

Repair from what?