Can we puh-leeeze lay that old folklore to rest now?
Every time I read some amateur nutritionist or armchair athlete telling people to force themselves to drink eight glasses of water per day, I want to scream. Swinging a dead cat around your head would be just as efficacious for your health, and probably better for your triceps and biceps.
This is not to say that you shouldn't replenish sweat and electrolyte losses during exercise. You should. And the losses are probably more than you think, unless you do a weigh-exercise-weigh procedure. But otherwise, there's no need to force down that 64-ounce jug of water on your desk every day. And no benefit, either.