"Invented by the French and used by virtually every elite athlete on the planet, it is often confused with some kind of torture. Right after working out, hop into the shower. First, cook yourself for no longer than 5 minutes in hot water, relax, get those blood vessels well dilated. Then slowly add cold water to the mix until it's so cold you can't stand it. Endure it. Focus the water on the back of your head and the muscles you just worked. Feel the blood vessels constrict. Stay under it for as long as it takes to really cool off - 2 to 3 minutes. The time it takes to cool down will increase as you adapt, and the temperature for cooling will decrease. Then, switch the hot water back on. The blood vessels will dilate, and inrushing blood will flush the lactic acid out. Start the cooking process again. Repeat at least two cycles and finish on cold. This induces a tonic effect and you'll rebound, flushing again as your body warms up in your clothes."
I also use them after workouts, as described here: http://paleohacks.com/questions/995/what-is-the-deal-with-co...
"Invented by the French and used by virtually every elite athlete on the planet, it is often confused with some kind of torture. Right after working out, hop into the shower. First, cook yourself for no longer than 5 minutes in hot water, relax, get those blood vessels well dilated. Then slowly add cold water to the mix until it's so cold you can't stand it. Endure it. Focus the water on the back of your head and the muscles you just worked. Feel the blood vessels constrict. Stay under it for as long as it takes to really cool off - 2 to 3 minutes. The time it takes to cool down will increase as you adapt, and the temperature for cooling will decrease. Then, switch the hot water back on. The blood vessels will dilate, and inrushing blood will flush the lactic acid out. Start the cooking process again. Repeat at least two cycles and finish on cold. This induces a tonic effect and you'll rebound, flushing again as your body warms up in your clothes."