2006年NPR美国国家公共电台八月-Athletes Run Risk of Over-Hydrating

（单词翻译）

Training for a marathon or an Ironman, how much you drink is important. Of course, there's the risk of dehydration¹, but athletes now know they can also get into trouble by drinking too much which dilute² levels of sodium³ in the blood.

The death of one 28-year-old woman following the 2002 Boston Marathon led to new research and experts say to strike the right balance, the best strategy is to replace or put back in your body through drinking roughly the same amount of fluid or water weight you lose through sweat.

You don't have to, necessarily, have a perfect match. I mean, we, our goal is to try to keep somebody within, not dehydrated in more than 2% of their, their body weight.

It sounds straightforward⁴, stay less than 2% dehydrated. But how in practice can you tell? Douglas Casa is an athletic⁵ trainer and researcher at the University of Connecticut. He's got one strategy. We caught up with him yesterday morning at 6am just before his morning run.

What I'm gonna do is weighing myself, I'm new before I go running.

With an accurate scale, he'll be able to calculate exactly how much water weight he sweats out during his run.

Stepping onto the scale and my pre-weight right now is 63.3 kilograms.

Roughly 140 pounds. With that Casa was out his front door for an-hour-long workout. The focus on tracking dehydration stems in part from concern over a condition known as hyponatremia. This is when someone drinks so much fluid that concentrations of sodium in the blood drop off and the body can't function properly. A study published in the New England Journal of Medicine last year, tracked 488 runners who completed the Boston Marathon, and found 13% of them had dangerously low blood salt levels, twice as many women as men were at risk. Louise Maharam is a sports physician in New York, who chairs the International Marathon Medical Directors Association, he says the first symptoms runners may notice is a little swelling⁶ in the hands.

They can't get their rings off, then they may get nausea⁷, vomiting⁸, and may get dizzy, they may not remember where they are.

Most runners restore salt to normal levels by eating just one meal after a run and never need medical attention, but with a spate⁹ of reported cases of hyponatremia, Maharam's group has a new simple guideline for hydrating. It's contrary to the old advice that runners should drink as much as they can stomach to prevent dehydration.

The new research's shown that the body is a remarkable¹⁰ machine that actually tells you via a thirst when you need fluid.

In other words, drink only when you feel thirsty. For the more performance-oriented runners, Douglas Casa's method is certainly more exacting¹¹. After running one hour and drinking one liter of fluid, Casa hops¹² on the scale a second time.

I'll do kilogram test again; it is 63.0.

So Casa's lost just 3/10 of a kilogram, meaning that he successfully drank enough during his run to replace most of what he lost. Casa says there is no need to weigh every time after a handful of calculations taken under a variety of conditions. Runners get a sense of how much to drink to keep a steady weight.

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hyponatremia
低钠血症