Running

I'm sorry sharkstar, but thats wrong.

You do need rehydrating for any lengthy run , especially in cold weather, as you dehydrate at a similar rate, but you have a reduced thirst drive. *

On the note of early drinking in marathons, some people use it as a motivating force/ rhythm, plus, little and often (+electrolytes) = good hydration. Lots and infrequently (-electrolytes) = poor hydration.

Since recently I havent run past the distance that I know I need to rehydrate at, I no longer carry anything. But when I used to- I'd stash a bottle somewhere on a loop based run.

• this is due to peripheral vasoconstriction (non-essential blood supply shut off to reduce loss to cold) masking the volume loss in the central baroceptors (pressure centres in aorta[high P], and veins [low P]), which means reduced ADH (vasopressin/ anti diuretic hormone, increases water reabsorption), which is related to thirst, and can reduce thirst (which is a relatively late stage in dehydration) by 40%.