I've done this before and recently got back into it again. Huberman has talked about it as a way of increasing one's response to stress. It's also a meditation. I followed along with the video for a week and don't need it now.
https://www.youtube.com/watch?v=f0pGZLx ... KitaroWaga
I also started taking cold showers that Wim Hoff recommends although not when I'm feeling too stressed, starting to get sick, or am sick. It's also a meditation. I used to do 5 minutes but didn't get my head wet. I do now which increases the difficulty. I'm up to about 40 seconds. Huberman said 11 minutes a week total spread over 4 sessions is good enough for the research showing benefit.
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