For years athletes were told to drink as much as they possibly could before a long endurance event such as the marathon.

Dehydration had to be avoided at all costs.

This line of reasoning has been seriously altered over the past several years.

The dangers of hyponatremia or "drinking more than you're using" is now front and center. Hyponatremia in a worst case scenario can lead to coma and even death.

Hyponatremia is caused by drinking so much that you dilute the sodium content of your blood.

Some of the signs are nausea, headache, muscle cramps, confusion and seizures. Medical help as soon as possible is imperative.

According to a mayo clinic fitness specialist endurace athletes used to drink enough to "stay ahead" of their thirst. As a result, they were drinking more that they were losing through sweating.

Of course you can't allow yourself to become dehydrated as that brings on a whole new set of complications. The key is to take in as much fluid as you use and keep an even balance.

The International Marathon Medical Directors Association recommends that, during extended exercise, athletes drink no more than 31 ounces(or about 800 mililiters)of water per hour.

That seems to fall exactly in line with one of the best Ironman results I ever experienced.

I used one full water bottle between aid stations on the bike. During the run all I took from the aid staions was one styrofoam cup of water. Nothing to eat--nothing else to drink for the marathon. Assuming the cups hold around 5 ounces of water and the aid staions were 1 mile apart and I was running an 8:30 pace, my intake was pretty well right on 30 ounces per hour.

It doesn't seem like much fluid, but it was perfectly balanced I guess because the marathon time was 3:34 and I never had any sort of hydration problem during the entire run. So I suppose I luckily hit right on the perfect balance and what I took in was what I was using.

So, some things to remember:

-don't "over-hydrate" before the race start. I don't believe you should feel fluid sloshing around in your stomach. Also, you shouldn't have a bloated feeling. If that's the case, you've probably taken on more fluid than necessary. Plus for the Ironman, it makes for an uncomfortable swim.

-drink enough to avoid dehydration. Don't undercompensate. Its a fine line between dehydration and hyponatremia. Experimenting with your fluid intake will help you find what's best for you.

_according to studies, the optimum amount of fluid intake is approximately 31 ounces per hour of sustained physical activity.

-the chances of dehydration are greater than hyponatremia, but both can lead to serious compications, so finding the proper fluid intake balance for you cannot be overstated.