Hydration: The Key to Exercise Success (cont.)

During fitness classes, "I constantly remind people to drink," he says. You should work through a water bottle within 45 minute of any class.

The best way to tell if you are dehydrated is to check your urine, he says. "If your urine is pale to very clear it's a pretty good indication that you are well hydrated, while darker, more concentrated urine suggest you may be dehydrated."

But beware: Guzzling too much water can also cause serious problems for summer athletes. Drinking excessive amounts of water can cause a rare, life-threatening condition called hyponatremia, experts tell WebMD. It's often coined "water intoxication" and has been getting a lot of attention of late. As hikers, runners, and sports enthusiasts "get" the message about staying well hydrated, increasing numbers become overly hydrated. At this year's Boston Marathon, the majority of the 240 cots in the medical units were filled with dehydrated runners. By contrast, hospital officials reported a single case of hyponatremia in this year's marathon.

Hyponatremia refers to low levels of salt in the blood. This occurs when someone drinks so much water that they dilute the sodium in their blood. Low sodium levels can cause a clouding of consciousness, nausea/vomiting, lightheadedness, dizziness, and in severe cases, seizures, unconsciousness or death. The condition is less likely in the weekend athlete, but those participating in endurance sports like marathons are at higher risk and should take precautions.

Drinking no more than eight ounces every 20 minutes -- as Jeri Salazar does -- provides enough but not too much fluid, Maharam says. He is one expert who believes that "the risk of dehydration, even in the heat, is far less than developing hyponatremia." Why? Although dehydration is more common, hyponatremia can kill. One easy way to stay safe during a race: Don't drink water at every station, he advises.

Publicity about hyponatremia, however, raises concerns among many trainers, who say that dehydration remains the key problem for summer athletes.

"It is a very real problem, and you have athletes saying, 'I don't what to get hyponatremia,' and invariably they end up not drinking enough and get dehydrated," von Frohlich says.

Adds Jeri Salazar: "Many of the people I train initially believe that they should drink "as much water as possible" to avoid becoming dehydrated. However, more and more often these days, runners and the medical staff at races are being warned about the dangers of over-hydrating when running for an extended period of time."

"My runners ask me, 'How much should I drink?' I tell them, 'The answer lies in the process of determining individual fluid needs and developing a hydration strategy based on those needs,'" she says. "An appropriate hydration strategy can maximize running performance and reduce any risks of sub-optimal performance and or health issues."

Published June 10, 2005.

Sources: Jeri Salazar, Irvine, Calif. Adrian Cohen, MD, Neutral Bay, Australia. Eric von Frohlich, group exercise instructor, Equinox, New York; chief exercise officer, roadfit.com. Lewis G. Maharam, MD, medical director, ING New York Marathon.

©2005 WebMD Inc. All rights reserved.

Last Editorial Review: 6/30/2005 1:25:15 PM