Does anyone do this?
I've read up a little on it and it appears it has merit.
Jumping between hot and cold water seems the best way to go about it. Hot water brings blood to the skin surface, then hitting the body with icy cold water forces the blood back deep into the body. This promotes blood flow and is particularly affective at helping with muscle strains. And there is no healing in the body without blood flow they say.
The best example is those crazy lunatics who go for naked swims in those icey lakes when its snowing for purely health benefits it gives them.
Then on saunas .... they increase body temperature. Every degree of temperature doubles the white blood cell count. At 104 F the immune systems efficiency increases 64 times. It also explains how fever is how the body heals itself to destroy antigens.
Being in the cold Canberra winter I've cycled between hot water showers and then throwing the tap onto the icy cold. If you ever want a true test of discipline this is it. I can only manage it three or so times before giving up and not trying it again for weeks. I think its just too much for me, maybe i'll try it in Summer when the cold water is warmer

Apparently it also strengthens your nerve force after a while.
Needless to say after actually doing the hot/cold cycle my body felt one million dollars, and a complete overwhelming of energy through the body.
I think it has true value, just a shame i'm such a coward when it comes to Canberra's winter cold water showers

An easier thing to do is an icy cold foot bath apparenly rejuvenates all organs in the body via the reflex points in the foot.