Originally Posted by
wphamilton
It's not clear to me that keeping the water cold is has a significant effect on cooling the body. It's clear that there is some effect as the cold liquid absorbs heat energy up to body temperature, but I suspect that the actual amount is not much consequence. From the back of my envelope it looks like even drinking a liter (34 oz) of ice cold water you'd get in the range of 1°C at most. Also I'm not sure that the digestive system doesn't actively start to warm the water, and expend energy doing so, which would reduce the cooling effect you'd expect from simple thermodynamic transfer.
So I wonder whether it's really worthwhile to try to keep the water cold as long as possible for cooling purposes. Isn't it mostly just a habit - American habit - to prefer iced drinks?
It's not necessarily a physical cooling but more psychological and perhaps physiological . Drinking tepid bath water isn't nearly as pleasant nor refreshing as drinking ice cold water. Your mouth has lots of nerve endings that sense heat and cold. When you are hot, the nerve endings are "saturated" with the heat feeling. Cold drinks change the state of the nerve endings and we find it pleasant and want more. The cold feeling induces us to drink more which is better for us. I know that people drink hot drinks during cold weather but I doubt that most people would do it after or during exercise.
I welcome you to experiment. Pick a good hot day and go for a ride with ambient temperature water. Then switch to ice cold water at about the half way point. See if there is a difference. I certainly notice one.