单项选择题

Passage Two

Drinking too much fluid when exercising vigorously—which is often recommended in training—can actually kill you, sports medicine expert Timothy Noakes has warned. He says that drinking too much is unnecessary and can be fatal. “Perhaps the best advice is that drinking according to the personal need of thirst seems to be safe and effective.”

Noakes cites the example last year, when a woman in the Boston marathon died from a severe lack of salt in the blood because she drank too much sports drink before and during the race. Her death was not an isolated incident. Similar cases occurred in athletes, army personnel and hikers.

Conventional thinking has been that thirst is not a good indicator of how much fluid we need, and is actually a late signal of severe fluid loss. This has led to doctrines where athletes are encouraged to drink more than they want to.

Now, a new set of guidelines based on evidence has been developed, and recently adopted by USA Track and Field. It says the average person should probably be drinking between 400 ml and 800 ml in an hour in most forms of recreational and competitive exercise. People gently exercising in a mild environment would probably need less, and professional athletes competing in warm environments at higher intensities would probably need more. Cool drinks are absorbed more readily by the exercising body than warm drinks, and those containing sodium, such as sports drinks, are also more quickly absorbed.

The best title for this article would be _____.