The first time I had a ice bath was two months ago, since then I have been using them on any bike rides 2+hours, and any runs over 7miles. The next day I always feel great. I ran 15miles recently, and felt good enough the day after to still train.
They help recovery time, by contracting your blood vessels and slowing blood flow. When you then warm up, blood quickly rushes back and helps ‘clean’ out waste by-products of the damage done by running, working out, riding hard. Anytime you work out you create micro-tears and essentially destroy your muscle. You then get bigger, stronger, faster during the recovery process.
I fill the tub, with cold water and then add ice. Sometimes if I dont have ice I just use cold water. I can easily stand the cold water only. The ice adds a good amount of extra chill, I enjoy the baths. Some people can not stand the cold as well, and dress warm up top. I choose not too, and will even eat a post-workout PB&J sandwich while I sit/lounge.
When I was in Hungary a few years ago, I went to a bath house, and then had a horse shoe shaped ice bath, that was designed for people to walk into and then quickly out. I loved staying in there, until I would almost black out and then going back into the saunas.