運動不要多喝水?

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

　　跑步和自行車等耐力運動的運動員已習(xí)慣于聽到要補充足夠水分的勸告。盡管保持身體有足夠水分很重要，但有時候你可能會攝入過多的水分。

　　Last summer, for example, I began experiencingunusual muscle cramping in my hands and legs longafter I finished a run, even the next day. Followingthe 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 theHospital for Special Surgery in New York, describe how he had nearly crashed during his firstIronman race. It was a hot day, Dr Metzl recalled, and he was saved by a bearded bystanderwho was handing out raw salt.

　　比如，去年夏天，我開始在跑完步很長時間后(乃至第二天)出現(xiàn)手部和腿部肌肉痙攣。我遵循一般的建議增加了水分攝入，吃富含鉀的香蕉。然而問題沒有解決。之后我聽了紐約特殊外科醫(yī)院(Hospital for SpecialSurgery)運動醫(yī)學(xué)專家約爾丹•梅茨爾博士(Jordan Metzl)講述他在第一次參加鐵人三項賽時差點暈倒的事情。梅茨爾回憶，那天天氣炎熱，一個蓄著胡須、正在分發(fā)粗鹽的旁觀者救了他。

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

　　如果你關(guān)注醫(yī)學(xué)方面的新聞，你很可能聽說過英美兩國旨在警告人們不要攝入太多鹽分的宣傳活動。的確，預(yù)制食品中往往含有大量鹽分，鈉可能會升高你的血壓，高血壓可能導(dǎo)致心臟病發(fā)作。

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

　　但梅茨爾表示，自行車運動員和跑步運動員面臨著截然不同的問題——鹽分攝入太少。梅茨爾參加過30次馬拉松比賽，著有為運動員撰寫的醫(yī)學(xué)參考書《跑步者健康指南》(Running Strong)。天氣炎熱潮濕的時候，大多數(shù)人會在鍛煉中大量出汗。身體非常健康的運動員實際上會比其他人出汗更多，這聽起來似乎有悖直覺，但這其實能夠幫助運動員降低體溫。

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

　　在運動員中，有一類人被梅茨爾稱為“多鹽流汗者”(salty sweaters)，這類人在鍛煉中不僅會比大多數(shù)人出更多的汗，而且他們的汗液中含鹽量也大得多。對此我有親身體會，我的汗液中含鹽量很大，以至于有時候會刺痛我的皮膚。

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

　　當你流汗的時候，自然反應(yīng)是喝更多的水，尤其是在那種設(shè)置了路邊飲水桌的比賽期間。但如果你只攝入水，不攝入鈉、鎂、鉀等電解質(zhì)，你會使問題變得更糟。水會稀釋你血液中本就因為出汗而減少的鹽分。

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

　　血液中鈉含量過低會導(dǎo)致一種叫做“低鈉血癥”的病癥。人們直到1985年才發(fā)現(xiàn)這種病癥。低鈉血癥的早期癥狀是手腳小肌肉群痙攣，就像我曾經(jīng)經(jīng)歷過的那樣，然后是腿部肌肉痙攣。如果癥狀持續(xù)惡化，你可能會神志不清，在極端情況下甚至可能死亡。

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

　　《英國運動醫(yī)學(xué)期刊》(British Journal of Sports Medicine)研究了這個問題，并敦促耐力運動員確保他們在訓(xùn)練時攝入足夠的鹽分，但這份期刊還警告稱，“如果液體攝入總量超過出汗量，補充電解質(zhì)只能減緩、但無法阻止低鈉血癥的形成”。換句話說，不要喝太多水。

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

　　遺憾的是，很多商業(yè)品牌的電解質(zhì)運動飲料都含有大量的糖，如果你跑步是為了保持身材，喝這種飲料會適得其反。幸運的是，現(xiàn)在有High5 Zero、Nuun這樣含鈉但不含糖的電解質(zhì)片劑。你要在開始耐力運動之前和之后服用這類片劑。

　　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 saysthat for most endurance athletes, having too little salt in the blood poses a far greater riskthan having slightly higher blood pressure for a day or two.

　　有些人可能會擔憂，攝入電解質(zhì)可能會升高血壓;的確，患有心臟疾病的人士應(yīng)該在服用前咨詢他們的醫(yī)生。但梅茨爾表示，對于大多數(shù)耐力運動員而言，比起血壓在一兩天內(nèi)略微升高，血液中鹽分太少造成的威脅要大得多。