I continue to use my Far Infrared (FIR) Sauna 2-3 times per week. I feel fairly confident it is helping detoxify my body. One thing I'm absolutely certain about: it improves my sleep. I always have a better night's sleep after a sauna session.
Yet there was a mystery I could never solve: why do I sometimes emerge from the sauna drenched in sweat and other times I barely sweat at all. The times when I came out dripping with sweat were the times when I felt better and slept better afterwards. Thus I felt it was important to figure out how to have the full-sweat experience every time. Up until recently, my leading theory was that a low-sweat sauna session meant I was dehydrated.
I finally figured out recently that there is a correlation between the times I pre-heated the sauna and the times I sweated more in the sauna. I vaguely recall that when I purchased the sauna, the manufacturer told me to heat it before getting inside. As the years went by, when I didn't have the patience to pre-heat the sauna, I started getting inside as soon as I turned it on and then I would wait for it to heat up while I was inside. I would add time to the end of my sauna session to make sure I still got a full half hour of maximum heat.
Just as they say frogs don't know they're being boiled alive if you start them in cold water and slowly increase the temperature (I wouldn't know, I've never cooked frog), the human body seems much less reactive to heat if you bring the temperature up slowly. Based on my experience, it's critical to getting the most out of my FIR sauna to "shock the system" by getting into an already hot sauna.