This article was originally posted by Ryan at the original HillRunner.com Blogs.
Back in 2002, a local runner told me with pride how he finishes all his marathons weighing more than what he did at the start. He was incredibly proud of this and insisted that I would be far better off if I followed his fueling plan. The idea was simple: the more hydrated you are, the better you run.
At the time, though, that idea bothered me. If you’re starting well hydrated or even slightly over hydrated as most runners do, why do you want to be even more hydrated at the finish line?
As it turns out, I was on to something. Since that time, we’ve seen a major change in opinions on hydration. Hyponatremia caused by overhydration has become a major concern and research has shown that moderate dehydration does not affect health or performance. In fact, some research has shown that the fastest marathoners finish fairly significantly dehydrated.
Now, the problem is creeping into other sports. It’s the same problem, people being told they must "get ahead of" dehydration and drink before they are thirsty.
The fact is we now know thirst is a very good indicator. You don’t need to get ahead of thirst. In fact, if you get too far ahead of thirst, the consequences can actually be far greater than if you fall behind.
This doesn’t mean you shouldn’t make sure you’re staying well hydrated. Just be careful to not overhydrate. And, while you’re running, there’s no problem with drinking to thirst.