Well I have no medical or scientific knowledge about the subject but. . .
I carry a 2 liter hydration bladder. Sip on it throughout the day and re-fill it just before heading out in the morning, at lunch, before dinner, and after dinner. Basically I consume 6-7 liters of water in a 24 hour period while backpacking 20-24 miles a day.
I've never been dehydrated while hiking never had a muscle cramp, and never been sore the next day. I have no idea if the amount of water I drink has anything to do with this but I am a big guy with a good deal of muscle.