Regular sauna bathing has been a staple of health routines in countries such as Finland for thousands of years. Two basic types of saunas exist. One is called an Infrared sauna, in which the body is heated directly from infrared lamps that emit electromagnetic radiation. This type of sauna is more of a modern invention. The more traditional sauna also called a "dry sauna," works by heating the air around you. One difference between the two is that IR saunas work at a lower temperature compared to dry saunas. The temperature is usually between 120 and 140 degrees. You can stay in them for a longer duration compared to dry saunas, with the average time being 20 minutes. The temperature in a dry sauna ranges from 150 to 195 degrees, so about 15 minutes is enough for that type of sauna.
One often stated benefit of sauna bathing is that it appears to offer some degree of cardiovascular protection. A 2015 study that examined the cardiovascular effects of sauna bathing in 2,315 Finnish people with an age range of 42 to 60 and followed them for 20 years, found that engaging in sauna bathing reduced the incidence of sudden cardiac death; coronary heart disease; cardiovascular disease; and death from cardiovascular disease. How does it do that? Regular sauna baths lower blood pressure and increase the strength of the left ventricle, the pumping chamber of the heart. The increase in sweating from being in the sauna causes a loss of fluid and an increase in heart rate. Indeed, some studies have compared the effects of sauna on heart function to that of aerobic exercise because of the way that saunas increase the heart rate. That, however, is hyperbole because aerobic exercise does more than just increase the heart rate, it also strengthens the heart muscle itself. One recent study even found that aerobic exercise can help to maintain the length of telomeres in the heart muscle cells. What that means in a practical sense is that aerobic exercise can keep your heart younger.
The heating of the skin in the sauna is what causes to heart rate to increase, and with a warm, dry sauna, the heart rate can increase to 150 beats a minute, again comparable to what happens when you do aerobic exercise. But while cardiac output increases by 60 to 70% in a sauna, the cardiac stroke volume does not change, as it does when you do actual exercise. The Finns like to expose themselves to cold temperatures right after emerging from a sauna. This activates the sympathetic nervous system, leading to the release of catecholamines such as epinephrine and norepinephrine, which constrict the blood vessels. The cardiovascular changes that occur when the body is exposed to cold are the opposite of what occurs in a sauna. As such, the heart rate decreases, while the stroke volume or the pumping of the heart increases. So does blood . . .