i wonder if there are studies about hot bath. Onsen are extremely popular in japan, and i'm absolutely certain the relaxation you get from hot water is beneficial to health as well
> cold showers can be dangerous for people with per-existing heart conditions
I think cold showers trigger the diving reflex[0] ("most noticeable effects are on the cardiovascular system, which displays ... in humans, heart rhythm irregularities"). I don't have a real source for that, but I tried cold showers a few times and found it impossible to breathe when I had cold water spraying on my face, like I could feel my airway closing involuntarily. Warm/hot water doesn't do that.
I know I have a heart condition (atrial fibrillation) and extreme cold, just like extreme heat, triggers my heart in ways I surely want to avoid at all times.
I've only heard about them (I think from Dr. Rhonda Patric) but I believe that there are studies showing that extreme temperatures in either direction have positive effects.
I'm sure I read somewhere that cold showers can be dangerous for people with per-existing heart conditions too.
I can't cite either right now but they should be easy to find with a Google search.