Hydration and Exercise: How to Get It Right
Consume the right amount
Clark says there isn’t a set amount of water that you should consume during exercise, rather, she recommends you “drink to thirst.”
But there are ways to calculate your sweat rate, which involve weighing yourself before and after you run, and doing a few calculations. Clark says that if you lose a quart of sweat in an hour then you should be drinking about eight ounces of water every 15 minutes.
If you want to skip the math and you tend to sweat a lot, 4 to 6 ounces every 15 to 20 minutes during your workout is a good rule of thumb.
Next: Don’t drink too much