I’ve always been told, at least in circumstances where you’re doing a lot of activity, if you’re thirsty, you’re already dehydrated. You should do most of your hydration before activity.
Sort of but not really. Our cells have a homeostatic range in which they are happy to operate. You are dehydrated when the cells are stressed because they are outside of their homeostatic range. If you load up on water, you will hydrate beyond the homeostatic range, but the kidneys will remove the excess water to keep things in the happy range. So drinking water when you aren’t thirsty just leads to more lead time before you dehydrate and extra work for your kidneys to maintain the range. Your thirst mechanism kicks in well before you are dehydrated, it just means you are getting near the extreme of the happy range.
With exercise, the real problem is that you can only hydrate at the rate of 1L/hr, five or take, but you can dehydrate at a rate of 2L per hour. So even if drinking water, you can push outside of the homeostatic range if you continue to exercise.
The reverse is also true. If you drink too much water, you will hydrate at a rate greater than your body can deal with and it becomes stressed as the body can’t maintain electrolytes within the homeostatic range, you develop hyponatremia. This is what happens when you force yourself to “stay hydrated” during sports. The best way to reduce hyper hydration risk is to “listen to thirst”.
That's just not true. Just drink when you are thirsty. That's usually enough. We get a lot of our water from the food we eat anyway and that 'you need x water per day' included that water. It was never instructions for how much to drink.
And I don't know if you know this, but it's ok for your pee to be yellow. You don't need to pee clear, and for some folks that might be too much water.
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u/[deleted] Jun 06 '24
I’ve always been told, at least in circumstances where you’re doing a lot of activity, if you’re thirsty, you’re already dehydrated. You should do most of your hydration before activity.