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Hydrate, but make sure you don't drink too much water, either

Pam LeBlanc, Fit City

Staff Writer
Austin 360

Athletes hear it all the time: "Drink all you can, even before you feel thirsty." But drinking too much water and not enough electrolytes can be just as dangerous as dehydration.

Earlier this month, a paddler racing in the multi-day, 260-mile Texas Water Safari from San Marcos to the Texas coast died from what race organizers attributed to hyponatremia, or too little sodium for the amount of water in his bloodstream.

It used to be relatively rare. With more athletes participating in Ironman Triathlons, ultra marathons and other endurance events, though, hyponatremia is becoming more common.

When it's hot, athletes can sweat out a liter of fluid — between 1 to 2 grams of salt per liter — every hour. If the salt isn't replaced, the delicate blood-sodium balance gets disrupted. A 2005 study published in the New England Journal of Medicine of nearly 500 runners who finished the Boston Marathon found that 13 percent had developed hyponatremia by the end of the race.

Hydrating without overdoing it can be tricky.

"It takes a lot of vigilance and knowing your own body, and it's not always easy," says Dr. Pierre Filardi, a longtime runner, Ironman triathlete and medical director of the Livestrong Austin Marathon.

Unfortunately, the symptoms of hyponatremia and dehydration can look a lot alike: nausea, muscle cramps, disorientation and confusion. If you are developing hyponatremia and you drink water, though, you'll get sicker. Hyponatremia can lead to seizures, coma or death. That's why some experts now question the whole "drink as much as you can" philosophy.

The key? Try not to drink more than you sweat.

Some experts recommend a standard amount, such as drinking 24 ounces of fluid an hour. But every body is different, and most people can only absorb between 1 and 1.5 liters of fluid an hour while exercising.

Another strategy is to figure out how much you sweat. It's easy to get a rough estimate by weighing yourself before and after a run, while accounting for whatever you drink along the way. Go to http://bit.ly/Mqy2VS to learn how to calculate your sweat loss.

To avoid over-watering, some experts are now going back to the old rule of thumb of drinking just as much as it takes to quench your thirst.

Filardi suggests drinking sports drinks with electrolytes (like Gatorade or Gatorade Endurance, which has even more sodium) instead of plain water whenever you exercise in the heat for long periods of time.

"It doesn't hurt to drink water for outdoor exercise up to an hour or hour and a half. But our environment is so extreme that beyond an hour and a half, why not just start out with an electrolyte drink? There's no reason it will hurt you," he says. "Your body can handle a little dehydration better than it can handle over-watering."

Pay attention to your urine, too. If you're urinating a lot and it's clear, you may be overhydrated. If you're not urinating much and it's dark yellow, you may be dehydrated. Your urine should be somewhere in between — light yellow.

Finally, know when to pull the plug. If you don't feel well, stop and cool off.

"When the heat and humidity are high, we have to be really wary about any exercise that's going to exceed one hour because you're much more likely to get dehydrated, overheated or, if you're drinking a lot of water, hyponatremia."

If you want to read more on the subject, Tim Noakes, a South African professor of exercise and sports science and author of the "The Lore Of Running," recently released a book called "Waterlogged: The Serious Problem of Overhydration in Endurance Sports" (Human Kinetics, 2012).

Contact Pam LeBlanc at pleblanc@statesman.com or 445-3994 Twitter: @fitcityleblanc