Okay all to the ones who will laugh about this and thinking that it's really stupid, this actually helps you in your game. Warmer hands = better blood circulation in hands -> making 'em more responsive. Starcraft players have been using this for a really long time to get their hands ready for some 400 APM.
tried to play serious with really cold hands? you cant even play csdm and this is like, one of the biggest tournaments...
your reflex and aim would suck, you couldn't kill a single guy