Among the surprises in my reading was learning that teams of Japanese doctors are spearheading research in the use of sauna to treat cardiovascular problems. In Japan, short treatments (about 15 minutes) with a dry sauna at 60°C (140°F) are called “Waon” therapy. Waon is Japanese for “soothing warmth.”
Another surprise is that they and other researchers are using far-infrared saunas, sometimes called FIRS. Why?
In response to someone else’s question “What is a far infrared sauna? Does it have health benefits?” Brent A. Bauer, M.D, wrote this: http://mayoclinic.org/infrared-sauna/expert-answers/faq-20057954
“A far-infrared sauna is a type of sauna that uses light to create heat. 'Far' describes where the infrared waves fall on the light spectrum. A traditional sauna uses heat to warm the air, which in turn warms your body. An infrared sauna heats your body directly without warming the air around you.
“The appeal of saunas in general is that they cause reactions such as vigorous sweating and increased heart rate, similar to those elicited by moderate exercise. An infrared sauna produces those results at lower temperatures than does a regular sauna, which makes it accessible to people who can’t tolerate the heat of a conventional sauna. But does that translate into tangible health benefits? Perhaps.
“Several studies have looked at using infrared saunas in the treatment of chronic health problems, such as high blood pressure, congestive heart failure and rheumatoid arthritis, and found evidence of benefit. However, larger and more rigorous studies are needed to confirm these results.
“On the other hand, no adverse effects have been reported with infrared saunas.”
In digging deeper, I learned that the air in far-infrared saunas is heated to 60°C (140°F) while in traditional saunas it’s about 85°C (185°F). With far-infrared saunas, the wave apparently heats more deeply than warmed air so FIRS users develop a vigorous sweat and an increased heart rate at lower temps. So that might make it more accessible for those with osteoarthritis or cardiovascular or respiratory problems.