Experts warn against excess fluids during exercise

NEW YORK (Reuters Health) - To guard against an increasingly common exercise-associated condition, athletes should be warned about the risk of drinking too much fluid, and athletes and coaches should be better educated about the signs and symptoms of exercise-associated hyponatremia (EAH), according to a new consensus statement.

"The incidence of EAH is increasing at an alarming rate and is arguably the most prevalent serious medical condition encountered by endurance athletes over the past decade," Dr. Tamara Hew-Bulter, of the University of Cape Town in South Africa told Reuters Health. "We wish to draw attention to the morbid medical complications associated with drinking too much fluid, which are dire and have caused death."

Hew-Bulter and other members of Exercise-Associated Hyponatremia Consensus Panel reviewed available research in an effort to provide reliable information on the topic to health professionals and the general public. The consensus statement was published in this month's issue of the Clinical Journal of Sport Medicine.

Exercise-associated hyponatremia occurs when sodium levels in the blood drop below normal levels, or about 135 mmol/liter, in most cases. The condition is most commonly associated with physical activity lasting more than four hours.

Many early signs and symptoms of the condition are similar to those for dehydration, and include nausea, vomiting, headache and bloating. As hyponatremia progresses, signs can include altered mental status, such as confusion and disorientation, seizures, respiratory distress, coma and even death.

Published research shows that the best way to avoid the condition is to refrain from drinking excessive amounts of fluid -- water or sports drinks -- while exercising. In fact, limiting the availability of fluids during races, with aid stations placed at every five kilometers, rather than smaller distances during a standard marathon, for example, has been shown effective in reducing the incidence of the condition.

Also, Hew-Bulter and her colleagues note, medical facilities at endurance events should be equipped to analyze athletes' sodium levels and to provide appropriate treatment if they fall below normal limits.

Hew-Bulter considers exercise-associated hyponatremia more dangerous than dehydration, which is "more of a detriment to performance than it is to health." However, she stresses that "the EAH Consensus panel is not recommending that athletes refrain from drinking during exercise."

"We aim to encourage athletes to shoot for a middle ground in regards to drinking habits and rely on their body's internal cues rather than heed fixed fluid guidelines that cannot account for the wide variety of sports and athletes that are competing in endurance activities in a variety of climates," she added.

Commenting on the consensus statement, Dr. W. Larry Kenney, a Penn State University-based expert on hydration and related issues, said that exercise-associated hyponatremia is a very serious, but "an extremely rare phenomenon."

It is "far less common than serious dehydration," he told Reuters Health. To avoid experiencing either condition, however, the "idea is still to consume fluids to try to match sweating loss," he said.

"We want to encourage athletes not to go to either extreme -- not to overdrink (and) not to underdrink during exercise," said Kenney, a member of the American College of Sports Medicine.

SOURCE: Clinical Journal of Sport Medicine, July 2005.