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Many cultures swear by the benefits of a hot bath. But only recently has science began to understand how passive heating (as opposed to getting hot and sweaty from exercise) improves health.
At Loughborough University we investigated the effect of a hot bath on blood sugar control (an important measure of metabolic fitness) and on energy expended (number of calories burned). We recruited 14 men to take part in the study. They were assigned to an hour-long soak in a hot bath (40˚C) or an hour of cycling. The activities were designed to cause a 1˚C rise in core body temperature over the course of one hour.
We measured how many calories the men burned in each session. We also measured their blood sugar for 24 hours after each trial.
Cycling resulted in more calories being burned compared with a hot bath, but bathing resulted in about as many calories being burned as a half-hour walk (around 140 calories). The overall blood sugar response to both conditions was similar, but peak blood sugar after eating was about 10% lower when participants took a hot bath compared with when they exercised.
We also showed changes to the inflammatory response similar to that following exercise. The anti-inflammatory response to exercise is important as it helps to protect us against infection and illness, but chronic inflammation is associated with a reduced ability to fight off diseases. This suggests that repeated passive heating may contribute to reducing chronic inflammation, which is often present with long-term diseases, such as type 2 diabetes. Exciting new field of research
Passive heating for human health is a relatively new field of research, but some exciting results have emerged over the past few years.
Research from Finland, published in 2015, suggested that frequent saunas can reduce the risk of having a heart attack or stroke – at least in men. The idea that passive heating can improve cardiovascular function received further support when the University of Oregon published a study the following year showing that regular hot baths can lower blood pressure. Japanese onsen. TOMO/Shutterstock.com
In a second study, the same group looked at the mechanism responsible for these improvements. They found that passive heating raised levels of nitric oxide, a molecule that dilates blood vessels and reduces blood pressure. This has implications for treating high blood pressure and improving peripheral circulation in people with type 2 diabetes. As type 2 diabetes is associated with reductions in nitric oxide availability, passive heating may help re-establish a healthier nitric oxide level and reduce blood pressure.
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Prefer showers over baths, but miss the sauna I had in my old house. Would love a steam room in my place.
In all cases it is better to get up and move.
All cases.
I love a good bath, but who ever takes an hour-long one?
How do you even keep the water hot that long?
I know this. When I feel a cold coming on, I make a hot and spicy soup, take a hot bath, layer up and go to bed. Works every time.
AWESOME!!!!!!!!!!!!
No wonder the Japanese are so healthy.
Even more so, I used to love going to the public bath in Japan, taking in 30 minutes in the sauna at 130 F, rinsing the sweat off, and then sitting 10 minutes in a 40 F degree bath, and then repeating the whole process. Your skin and muscles snap like firecrackers the next day.
There used to be a “Health Club” in Anchorage that had exercise equipment, a dry sauna, a steam room, and a “cold plunge”. This was about 3 feet wide and 6 or 7 feet deep filled with 40*F water. There were hand rails and steps to help getting in and out. I would exercise, hit the dry sauna and steam room and then immerse in the cold plunge. I swear I could feel my peripheral blood vessels screaming in protest as they constricted. After I did that circuit twice I was a total noodle. Think about it - arteries are smooth muscle. They relax in response to heat and constrict in response to cold. My whole circulatory system was being exercised. Now I have a hot tub that I try to use at least every other day. Now how do I build a cold plunge?
