Thursday, August 27, 2015

When exercising, drink only when thirsty

Are we, with the best of intentions, putting young athletes at risk when we urge them to drink lots of fluids during steamy sports practices and games?

A new report about overhydration in sports suggests that under certain circumstances the answer is yes, and that the consequences for young athletes can be — and in several tragic cases already have been — severe and even fatal. ...

The problem with this situation is that, according to the latest science, dehydration during sports is rarely if ever dangerous, but overhydration undeniably is. ...

At least two other high school football players are known to have died since 2008 from drinking too much fluid during and after a practice, Dr. Miller said. These players had developed a rare condition, he said, known formally as exercise-associated hyponatremia and less technically as water intoxication. ...

The key, he said, is for athletes to drink when they feel thirsty — not before and not after they feel sated. “You do not need to ‘stay ahead of your thirst,’ as many people think,” he said.

Listening to your “innate thirst mechanism” provides a safe and reliable guide to hydration, the new report concludes.

This strategy also should not increase players’ risks for cramping or heat illness, Dr. Miller said, since, “based on current evidence, it does not appear that dehydration directly contributes” to those problems.

During recent telling experiments that he directed, for instance,volunteers who exercised and sweated in the heat until they had become severely dehydrated were no more prone to muscle cramps than they had been at the start.

Similarly, if perhaps more surprising, other studies have found that being dehydrated does not increase athletes’ susceptibility to heat problems, and that athletes who collapse from heat illness often are quite well-hydrated.

Instead, both cramping and heat problems seem to result from athletes pushing themselves too hard.
--Gretchen Reynolds, NYT, on the reliability of your thirst signal