Hydration for Athletes

https://www.webmd.com/food-recipes/features/quest-for-hydration#2

"The exact amount of water needed per day really depends on the individual," says Rick Hall, a registered dietitian in Phoenix. "People who exercise, for example, will lose a lot more water through sweat and breathing, so their needs are higher."

Athletes need to quench their thirst even when they're not thirsty, and avoid relying on the feeling of thirst to tell them when to drink.

"Headaches and cramping are common signs of dehydration," says Hall. "However, these are late signs. Unfortunately, the body hides mild dehydration very well, and it can take hours before you recognize that you are dehydrated."

Exercise, explains Hall, blunts the thirst mechanism.

"So folks who are running or biking may not feel thirsty when they actually need water desperately," Hall tells WebMD. "An important strategy is to prevent dehydration by hydrating frequently."