I had done it for a year and a half. I did it along with regular meditation, but have gotten lax on both for the past 6 months. I still take a cold shower every morning and I do feel good afterwards. I have also done 1 ice bath and it felt good for me, painful initially. I also intend to hop in Lake Michigan on New Years and stick it out as long as I can. I missed doing it last year as I had Covid, but maybe should have anyway.
The breath work started to feel like work for some reason, and I decided to take a break. I was trying to get longer hold times instead of just freeing my mind. I however will say when I was doing it regularly, I had a feeling of calm afterwards.
I'm pretty sure between meditation and the breath work my resting heart rate dropped noticeably. I was in the high 50's to low 60's, and after doing both for awhile I was hitting the high 40's and low 50's regularly. The nurse at last year's physical took my pulse 3 times as she was surprised it was 52 in the middle of the day.