Does a hard-working woman sweat like a man? That question, which has figured in many an antiperspirant commercial, has received surprisingly little scientific scrutiny. But a new study published this month in the journal Experimental Physiology provides persuasive evidence that women do sweat copiously during exercise. (Did anyone really believe they misted?) But fit women seem to sweat differently than unfit people of either sex, and quite differently than fit men, a fact that has implications for sports performance. It also may have some bearing on what it has meant, since prehistory, to be female.
一個勤奮工作的婦女出的汗像男人一樣多嗎？這個在很多止汗劑廣告中出現(xiàn)的問題，卻很少經(jīng)過科學的研究。但這個月發(fā)表在實驗生理學學報上的一項新研究提供了充分的證據(jù)表明在鍛煉時，女性會出很多汗(有誰真的相信嗎？)。但健康的女性出汗不僅不同于不健康的男性和女性，更不同于健康的男性。這可能說明了運動量的不同。也可能與作為女人有關。
For the study, researchers at Osaka International University and Kobe University in Japan recruited a pool of trained athletes, male and female, as well as an age- and gender-matched group of untrained volunteers. The men and women in the two groups were similar in terms of weight. All of the volunteers rode stationary bikes in a physiology lab heated to a balmy 86 degrees. The beginning of the hourlong session was leisurely; the pedaling intensity was only about 30 percent of each volunteer’s maximal oxygen capacity (VO2max). Then it became tougher, rising to 50 percent of each rider’s VO2 max, while the final 20 minutes required that the riders work at a strenuous 65 percent of his or her VO2 max. Throughout, researchers monitored how much perspiration the cyclists were producing on their foreheads, chests, backs, forearms and thighs. The researchers also determined how many sweat glands were active during each rider’s session. A person’s overall sweat rate depends on how many sweat glands his or her body activates and how much sweat is excreted at each gland.
為了研究的準確性，日本大版國際大學和神戶大學的研究人員找了一組經(jīng)過訓練的男女運動員，一組沒有經(jīng)過訓練的普通志愿者。兩組人的年齡和性別比例保持一致。兩組中同性別的人體重也差不多。所有的志愿者都在一個溫暖的(室內(nèi)溫度在86華氏[30攝氏])實驗室中騎固定自行車。在剛開始的一個小時內(nèi)，所有人都比較輕松。運動強度只達到每個人最大耗氧量的30%。接下來就更累了，強度提高到每個人最大耗氧量的50%。最后20分鐘，所有人的運動強度都達到了最大耗氧量的65%。在整個過程中，研人員監(jiān)控了志愿者額頭，胸部，背部，前臂和大腿上的出汗量，還確定了每個人在騎車過程中有多少汗腺在活躍。一個人的出汗率取決于汗腺的活躍數(shù)和每個汗腺的排汗量。
What the researchers found was that the fit men, unsurprisingly, perspired the most, significantly more than the fit women, especially during the more intense exercise. But the athletic men weren’t using more sweat glands. The fit women had just as many glands active and pumping; they produced less sweat from each gland. Meanwhile, the unfit women, by a wide margin, perspired the least, especially during the strenuous cycling, and became physiologically hotter — their core temperatures rising notably — before they began to sweat at full capacity. These results, the scientists concluded, “revealed a sex difference in the effects of physical training on the sweating response” and, just as important, “a sex difference” in “the control of sweating rate to an increase in exercise intensity.” In other words, the women, whether fit or not, were less adept of ridding themselves of body heat by drenching themselves in sweat.
研究人員發(fā)現(xiàn)，健康的男性毫無疑問出汗最多，遠遠超過健康的女性，特別是在運動強度加大之后。但這些男運動員并沒有使用更多的汗腺，健康的女性活躍的汗腺一樣多，她們每個汗腺排汗較少。同時，不健康的女性出汗最少，特別是在費力騎行的時候，她們先是體溫顯著升高，然后才開始大量的流汗?？茖W家推斷，實驗結果顯示了“體育鍛煉對出汗反應影響的性別差異”，同樣也說明“兩性在運動強度加大時控制自己身體出汗能力的不同”。換句話說，不管是健康的還是不健康的，女性更不善于通過出汗來降低自己的體溫。
Sweating is one of those bodily functions that seem uncomplicated, but it remains not fully understood by physiologists, at least in terms of how (and why) gender affects the process. “We know that fitness changes the sweating response,” said Timothy Cable, Ph.D., a professor of exercise physiology at John Moores University in Liverpool, England, who has extensively studied female athletes and how they perspire. As someone becomes more fit, his or her body begins to sweat at a lower body temperature. This is important, because “the body has a critical core temperature,” Dr. Cable said, which occurs at about 104 degrees, after which the brain simply “shuts down the motor cortex.” Unbidden, your legs stop churning and you curl up on the sidewalk until your core temperature drops (or a kind passerby calls 911). Sweating delays the onset of this critical heat buildup by dissipating the excess heat through evaporation. If you start to sweat at a lower temperature and increase your sweating rate as you get hotter during hard exercise, you’re less likely to reach the critical temperature.
出汗是那些看似簡單的生理機能之一，但生理學家仍然沒有充分理解它，至少在為什么性別會影響出汗這個問題上。“我們知道身體的健康度會影響人出汗”，英國利物浦約翰摩爾斯大學運動生理學教授Timothy Cable博士說。他廣泛的研究了女性運動員是如何出汗的。當某人變得更加健康時，他在體溫比較低的時候就開始流汗。這是非常重要的，因為人體有一個臨界溫度，Cable博士說，大概在104華氏(40攝氏度)，超過這個溫度之后，大腦就會關閉大腦皮層的活動。突然，你的腿就不能動了，只能蜷縮在人行道上直到體溫下降到臨界溫度，或者等路過的人打911。而通過汗液蒸發(fā)，可以散發(fā)多余的熱量，從而延緩臨界溫度的到達。如果你在體溫較低的時候就開始出汗，而且在劇烈運動中隨著體溫的升高會加大身體排汗量，你就不容易到達臨界溫度。
Scientists learned all that long ago. But they have yet to explain why women, even the fittest, don’t sweat as much as men, especially when they exercise at a high intensity. One answer, not yet definitively proved, seems to be “testosterone,” Dr. Cable said. Earlier studies suggest that the sweat rates of prepubertal boys and girls are roughly the same. Things begin to change when the sex hormones begin to circulate. Even then, men’s and women’s perspiration is similar in terms of water, salt content and smell, Dr. Cable said, strange as that may seem to anyone who’s been in close proximity to a young male athlete’s laundry hamper. (Sweat itself is odorless; the distinctive smell associated with sweating is produced by the waste products of bacteria feeding on the perspiration.) In an experiment conducted decades ago, male athletes were injected with estrogen and sweated less during subsequent exercise.
科學家很久之前就知道（這種現(xiàn)象）了，但他們還沒有解釋為什么女性，即使是最健康的女性，也沒有男性流汗多，特別是在高強度鍛煉中。“一個未經(jīng)證實的原因是睪酮素”，Cable博士說。此前的研究表明，青年期男孩和女孩的出汗率大致相同。當性激素開始流通之后，情況才會發(fā)生變化。即使這時，男人和女人汗液的水含量、鹽含量和味道也是相似的，Cable博士說，只有年輕男性運動員的汗液會有獨特的味道。(汗本身沒有味道，獨特的味道來自于生長在汗液中細菌)。在一項十多年前的實驗中，男性運動員被注射了雌激素，在接下來的鍛煉中汗就流得少了。
But does this difference in sweating rates, whatever its cause, have practical implications? “It appears,” said Yoshimitsu Inoue, Ph.D., a professor of physiology at Osaka International University and one of the authors of the study, “that women are at a disadvantage when they need to sweat a lot during exercise in hot conditions.” On the other hand, it may be that women, during evolution, had the good sense to get out of the hot sun, and their bodies adapted accordingly. The “lower sweat loss in women may be an adaptation strategy that attaches great importance” to preserving body fluids “for survival,” he wrote in an e-mail, while “the higher sweat rate of men may be an adaptation strategy for greater efficiency of action or labor.”
但出汗率的差別，不管是因為什么，有什么實際意義嗎？“看起來，”大阪國際大學生理學教授Yoshimitsu Inoue博士說，他也是這次研究的作者,“在熱的環(huán)境中鍛煉時，女性無法流很多汗，這是對其不利的因素”。而從另一方面說，這可能是女性在進化過程中，能有意識的避免烈日暴曬，從而相應地調(diào)整了自己身體的進化。女性低流汗率是一個重要的進化適應策略以防止體液流失，他在郵件中寫到，而男性的高流汗率是使干活更有效率的進化策略。
Dr. Cable agreed. “Prehistoric men followed the herds,” he said, whatever the temperature, while the women, cleverly, sought out the shade. “It’s not a bad survival strategy,” he said, even today.
Cable博士同意這種說法。“不管氣溫多高，史前男性會跟著牲畜，”他說，“而女性則會去找陰涼處躲避”。“即使在今天，這種生存策略也不錯”，他說道。
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