Projo Running Blog

With all this talk about being properly hydrated during exercise, is it possible to drink too much water?

Well, yes, it is possible. But you have to know the whole story before you go shutting off the faucet.

There is a condition known as hyponatremia _ which is a fancy word for low blood-sodium levels, says Dr. Douglas Casa _ in which an individual consumes so much fluid _ and only with water or low-solute beverages _ that his or her body cannot get rid of it fast enough and intracellular swelling occurs.

It is also sometimes referred to as ``water intoxification’’ and can lead to seizure, coma and even death.

Cases of hyponatremia ``tend to be more isolated incidents,’’ said Casa, the Director of Athletic Training Education at the University of Connecticut. It has been particularly known to happen in endurance events with back-of-the-packers or in the military when the soldiers are out on 10-hour hikes.

``The slower marathoners who take longer to finish are drinking more than they are sweating and they are diluting their sodium levels,’’ said Casa, who has served on the medical teams for both the Boston and New York City Marathons. ``These are the runners who take 4, 5 and 6 hours to finish. They’re more apt to stop at each aid station and drink at every one. You don’t see (hyponatremia) in elite runners because they’re running too fast. They’re not stopping and drinking at every aid station.’’

Making sure you maintain normal sodium levels is one way to help avoid suffering from this condition. This can be done through sports drinks and salty foods (such as pretzels or crackers) during the event and by including sodium in your meals. (Those with high blood pressure should consult their physicians.)

The biggest thing a person can do, said Casa, is to figure out during their training runs what their fluid needs are _ because everyone’s needs are indeed different.

The color of your urine is a good indicator, with a dark color meaning you haven’t hydrated enough, light yellow meaning you’re probably doing all right with fluid consumption and completely clear signaling that you are overhydrated.

Also, ``hop on a scale naked before the run and hop on it again after the run,’’ said Casa. ``If you’ve gained weight, you drank too much. That’s an easy way to get a feel for what our needs are.’’

While hyponatremia is a very real phenomenon, the opposite condition _ dehydration _ tends to be what most people encounter, he added.

``99.9 percent of the time, the bigger issue is not overhydrating, it’s not drinking enough,’’ Casa said. ``It’s a struggle to keep up your fluid needs. It can be a challenge to replace them all.’’

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