运动不要多喝水？

对于大多数长跑运动员来说，血液中盐分含量较少所造成的威胁，在短期内甚至比血压稍高造成的威胁更加严重。大量运动之前，掌握正确安全的方法更加值得被认真对待。

测试中可能遇到的词汇和知识：

endurance 忍耐；持久[ɪn'djʊər(ə)ns; en-]

injunction 命令；劝告[ɪn'dʒʌŋ(k)ʃ(ə)n]

intake 摄取量；通风口['ɪnteɪk]

muscle cramping 肌肉痉挛

potassium [化学] 钾[pə'tæsɪəm]

bystander 旁观者；看热闹的人['baɪstændə]

sweat 使出汗[swet]

irritate 刺激['ɪrɪteɪt]

electrolyte 电解质；电解[ɪ'lektrəlaɪt]

dilute 稀释；冲淡；削弱[daɪ'l(j)uːt; dɪ-]

counterproductive 适得其反的[,kaʊntəprə'dʌktɪv]

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Sweating runners must check their salt intake（578 words）

By Charles Wallace

* * *

Endurance athletes such as runners and cyclists are used to hearing injunctions to drink enough water. While staying hydrated is important, there are times when you can have too much water.

Last summer, for example, I began experiencing unusual muscle cramping in my hands and legs long after I finished a run, even the next day. Following the usual advice, I increased my water intake and ate bananas, which are full of potassium. That did not fix the problem. I then heard Jordan Metzl, a sports medicine specialist at the Hospital for Special Surgery in New York, describe how he had nearly crashed during his first Ironman race. It was a hot day, Dr Metzl recalled, and he was saved by a bearded bystander who was handing out raw salt.

If you follow medical news, you have probably heard the campaigns in the UK and the US warning about eating too much salt. It is true that there is often a lot of salt added to prepared food, and sodium can raise your blood pressure, which can lead to a heart attack.

But cyclists and runners face an entirely different problem — too little salt, says Dr Metzl, who has run 30 marathons and is the author of a medical guide for athletes called Running Strong . When it is hot and humid, most people tend to sweat a lot during exercise. Very fit athletes actually sweat more than other people, which sounds counterintuitive, but it helps cool them down.

There is also a subgroup of athletes whom Dr Metzl calls “salty sweaters”, who not only sweat more than most during exercise but also sweat much more salt. I know because I am one and my sweat is so salty it sometimes irritates my skin.

A natural reaction when you sweat is to drink more water, especially during races when there are water tables by the roadside. But if you are taking in water and not electrolytes, which include sodium, magnesium and potassium, you are making the problem worse. The water dilutes the salt in your blood, which has been reduced by your sweat.

Too little sodium in the blood can cause a condition known as hyponatraemia, which was only identified in 1985. Early symptoms of hyponatraemia are cramps of the small muscles in your hands and feet, like I had, followed by leg cramps. If the problem continues to worsen, you can become mentally disoriented and even, in extreme cases, die.

The British Journal of Sports Medicine looked at the problem and urged endurance athletes to ensure they get enough salt during exercise, but also warned that “electrolyte replacement will slow but not prevent the development of hyponatraemia if fluid intake is in gross excess of sweating rate”. In other words, do not drink too much.

Unfortunately, many of the commercial brands of electrolyte-laden sports drinks are loaded with sugar, which is counterproductive if you are running to stay in shape. Luckily there are electrolyte tablets like High5 Zero and Nuun available that contain sodium but no sugar. Take them well before you start your endurance event and after as well.

Some people may worry about raising their blood pressure by taking electrolytes; indeed, people with a heart condition should consult their doctor before taking them. But Dr Metzl says that for most endurance athletes, having too little salt in the blood poses a far greater risk than having slightly higher blood pressure for a day or two.

请根据你所读到的文章内容，完成以下自测题目：

1. Which one are full of potassium?

a. apples

b. water

c. durians

d. bananas

2. What kind of chemical elements can raise people’s blood pressure?

a. sodium

b. potassium

c. magnesium

d. mustard

3. Who actually sweat more than other people in the marathon as mentioned?

a. the extremely weak men

b. the old

c. very fit people

d. women athletes

4. What kind of behavior is encouraged before start endurance event in the author’s view?

a. drink enough water

b. drink High5 Zero without sugar

c. drink commercial sports drinks

d. wear less clothes

[1] 答案d. bananas

解释：水果中，香蕉含钾元素最多。

[2] 答案a. sodium

解释：生活中常被建议要减少盐的食用量，因为里面的钾容易使人血压升高，mustard是芥末。

[3] 答案c. very fit people

解释：文章中提到，非常健康的人在长跑中更加容易出汗，尽管和我们想象的不同，但是这种反应可以帮助他们在运动中降温。

[4] 答案b. drink High5 Zero without sugar

解释：作者建议在运动前后选择无糖的High5 Zero（一种电解质泡腾片），市面上的大部分商业品牌的运动饮料含有太多糖分。