LEWIS G. MAHARAM, MD: Hyponatremia is when your serum salt level is below a specific number in the blood.
When the salt level drops, initially, you become dizzy, faint, your sensoria may change. You then may have some nausea, vomiting, diarrhea. You also may have some syncope; that's fainting. Seizures, your brain starts to swell, you get pulmonary edema, and then eventually your brain stem will herniate and die if the serum sodium gets too low.
We're finding that hyponatremia in exercise happens most often, to runners and walkers that are out there on the course for long periods of time that stop at every water station along the course and drink like grandma told them to, drink, drink, drink, drink, drink. And if they stop at every water station along the course at these events, they end up getting hyponatremic.
So, how can runners estimate their fluid needs?
LEWIS G. MAHARAM, MD: Moderate to elite exercisers or even weekend exercisers don't need to estimate what their fluid needs are. That's another myth that is going by the wayside. Research shows that all you need to do is either drink for thirst or drink no more than one cup, eight ounces of a sports drink every twenty minutes while out exercising, but no more than that.
If you drink for thirst, the new research shows, then you're drinking plenty.
ANNOUNCER: So, where did the idea that we need to constantly hydrate during exercise come from?