I started training for my first marathon just about 2 years ago. I had been running for many years (like, really many; I'm old), but never running far enough to have to think about things like "hydration". I ran. Then I drank some water. And I was happy.  But when I started to train for a marathon and my distances started to extend, I realized, hey -- I'm getting thirsty. I didn't really think about it in terms of hydration, only in terms of thirst. 

I really wasn't ready to run my first marathon - in retrospect I was woefully unprepared. I made it, but I walked a lot. One thing that other marathon runners told me before that first one was, "stop at every water stop and drink at every one."  So I did. I dutifully drank a cup of water and a cup of the koolaid at each and every stop. Didn't know or care about "fuel" but that's not the point here anyway. I made it and that's all that mattered to me then.

Over the summer of 2007, my running partner and I started training in earnest for the fall Marine Corp Marathon. He was the one that started actually paying attention to hydration - he would carry an 8-oz paper cup with him and measure how much he drank at each of our water stops. But the mantra always seemed to be to drink more. Especially in the heat and humidity of DC summer. As our runs got longer, we started carrying more and more in the way of water bottles, belts, etc.   I now own three different belts, a camelback fannypack and a hand-held bottle. I can carry anywhere from 20oz to 64oz when I run. And, for a while, that's what I did. At the peak of my water intake regime, I was carrying 56 oz. to get me thu 5.5 miles during the DC summer heat. And it never seemed enough. I always seemed to want more.

Things reached a breaking point this past Spring at the Frederick marathon. I felt dehydrated the whole run and ended up with cramping and had to walk significant portions of the last 6 miles or so. But I noticed something odd -- even though I felt dehydrated, I had to stop (twice) to pee. How could that be?

Well, I took some time off training after Frederick and when I started back, I began to reseach the hydration thing a bit more. I got a scale and weighed myself before and after runs. And that data told me some things. But not enough.  I also read some interesting material from Hammer Nutrition about hydration. They hold with the theory that when we run, we can replenish some of the fluids (and fuel and electrolytes too) that we lose from long runs - but we can't replace them. They contend that us mid-to-back-of-the-pack runners tend to overhydrate because of the emphasis on "drink drink drink".  And that felt right to me -- that if anything, I was overhydrating. As I read about the problem, I realized that many of the symptoms I was ascribing to dehydration (like cramping) are also attributable to overhydration.

So, armed with this new vision, I cut way back on the fluids. I now consume less than half what I did (and I realize that the amount depends on all kinds of factors) and that what I consume is simply going towards the goal of replenishing lost fluids - I'm no longer trying to replace them.  In my new vision of hydration, I see my internals as like a sponge. As I run, it's getting wrung out. As I drink, some of what I drink is absorbed by the sponge, rehydrating it. The rest of what I drink runs off -- just as if I were to pour water on a sponge - some (or a lot, depending on how fast I poured)  would run off.

An important part of this vision is the realization of what this means for running over time, and especially in the heat. It means that there is a slow degradation which will eventually cause me to stop.  How soon depends on just how hot or humid it is. But it is inevitable. Part of training is to increase the amount of time I can go before that happens, but it will happen. It's just a question of time. But I've found that I can now run faster and farther using less water than before.

Now, if I could only figure out how to drink from those dixie cups while running - I always end up choking on the water!