[ssfsa]

Dont forget that you need to cool your body, so you sweat when you work out. Also, as you breathe harder, you'll loose more moisture through your lungs (the water activity of your whatever parts in the lungs being higher than that of dry air.)

If you were to exercise outdoors during a cold rain, you'll probably not loose any water at all.

But what do I know? I've never exercised in my life.