Hydration: The Key to Exercise Success

As a seasoned marathon runner, 36-year-old Jeri Salazar has her hydration needs down to a science. And well she should. In addition to being an executive at Disney, this Irvine, Calif., resident is also the Team in Training Marathon Coach for South Orange County and often preaches what she practices to a group of novice runners.

"I drink 64 ounces of water each and every day so I'm always in a well-hydrated state," she tells WebMD. In two days before the recent Boston Marathon, she included a sports drink replete with electrolytes as part her daily fluid diet. "I figured that getting the extra sodium and potassium in my system couldn't hurt, especially considering what a "salty" sweater I am," she says.

Turns out, that was a good call at this year's Boston marathon. An unusually large number of runners were treated for dehydration because the temperature reached 72 degrees. Fortunately, Salazar was not one of them.

But alas, dehydation is not the only problem that athletes may acquire. Too much water can cause a condition called hyponatremia which means that your sodium levels are too low. That's why it's crucial for athletes to strike the proper balance when it comes to hydration. Whether you're a marathon runner like Salazar or a weekend warrior, knowing precisely how much fluid to consume before, during, and after workouts -- especially in the heat of the summer - can help stave off both conditions.

Hydration in the Heat

"Staying hydrated is fundamentally important to a successful summer exercise regimen, in fact, for any activity," says Survivor consultant Adrian Cohen, MD, of Neutral Bay, Australia. As the medical advisor for many reality shows, including Survivor and Eco Challenge, Cohen has seen firsthand the havoc that dehydration can wreak on performers and performance. "Whilst we tend to focus on hard, sweaty workouts and long jogging sessions, even a brisk walk or a scratch basketball game in the hotter weather puts demands on the human body, and without the 'fuel' (water) the engine runs dry," says Cohen, author of several books including Survivor First Aid.

Successful, balanced hydration starts with prepping yourself for exercising in the heat, says New York City- based sports medicine expert Lewis G. Maharam, MD. "Take 10 days to two weeks to get used to hot weather, building workout intensity and duration gradually," he says. Engage in higher-intensity activities during cooler morning hours and do easier work during the heat of the afternoon, he suggests.

Choosing Your Hydration Fluid

If you are not running a race, "the rule of thumb is to drink 8 ounces of a sport drink or water possibly every 20 minutes," says Maharam, who advises the ING New York Marathon. No more, no less. "If you are exercising less than 40 minutes, water is fine, but for anything over 40 minutes, you want a sports drink that has sugar or salt in it because this helps you increase the fluid that goes into the body. Most sports drinks contain the equivalent of an "active pump" that gets more water into the body faster than the unassisted process - simple diffusion of water - would have.