Originally Posted by TheeJayBee
I'm not a science guy, but based on what I do know, it stimulates the blood flow and forces your body to circulate it more effectively to warm up.
I am a science guy so look at it logically. Cold shower would mean that blood is pumped away from the extremities to the organs so you don't lose too much heat. Its a principle that works with hot/cold showers, the blood is 'flushed' through your system from your extremities to your organs and back.