When it comes to exercise, many people seem to fall into two distinct camps: those who love a vigorous, sweat-soaked workout and those who view it as a form of torment.

　　说到锻炼，很多人立刻会分化为两大截然不同的阵营：一方喜欢大运动量、汗水淋漓的锻炼，另一方则将其视为一种折磨。

　　With hopes of getting more people up and moving, scientists are looking at the body's biological and chemical processes for clues to understanding what's behind differing attitudes toward exercise. That could mean there are factors beyond motivation and discipline to explain why some people enjoy exercising and others don't.

　　为了让更多的人动起来，科学家正在研究人体的生物机制和化学过程，寻找线索以理解人们对于锻炼持有不同态度的深层次原因。也就是说，除了动机和纪律之外，可能还有其他因素可以解释为什么有些人喜欢锻炼，而有些人则不喜欢。

　　One finding so far: How people interpret their body's sensations during and after exercise plays a large role in whether they enjoy it. Also, researchers at Iowa State University found that people's physical capacity could be much lower than many realize, so many people push beyond their limits without realizing it. For example, for sedentary people, just cooking dinner could count as exercise and they need to build up to even walking, the researchers found.

　　目前已有一个发现：人们对于运动期间和运动后身体感觉的认知会在很大程度上影响他们喜爱运动的程度。此外，爱荷华州立大学(Iowa State University)的研究人员还发现，许多人的体能极限可能比想象的要低得多，因此他们不知不觉就会超过自己的极限。举例而言，研究人员发现，对不好动的人来说，只是做一顿饭就算得上是一种锻炼，他们甚至连走路都需要耗费很大的体力。

　　Dan Cederholm has tried for years to find some type of exercise he could stick with. He finds the gym boring and basketball and baseball leagues unappealing. As for running? 'My shins always hurt like hell,' says Mr. Cederholm, 38, a Web designer from Salem, Mass.

　　多年来，丹•塞德荷姆(Dan Cederholm)一直想找到一种能够坚持下去的锻炼方式。他觉得健身房很无聊，对篮球和棒球又不感兴趣。跑步呢?“每次跑完步，我的腿都疼得要命。”38岁的塞德荷姆住在马萨诸塞州的塞勒姆市(Salem)，是一名网页设计师。

　　His friend Rick Johnson, on the other hand, competes in 20 road races a year. He remembers that even as a kid, when he was told to run a lap during gym class, he would ask to do extras. 'To me, it seems very foreign to say I don't enjoy sweating or running,' says Mr. Johnson, 41, an editor who also lives in Salem.

　　他的朋友瑞克•约翰逊(Rick Johnson)则恰恰相反，他每年要参加20场公路赛跑。他记得自己小时候上体育课时，老师要求跑一圈，他会主动要求多跑几圈。“对我来说，如果觉得流汗和跑步不爽，那就太奇怪了。”41岁的约翰逊是一名编辑，也住在塞勒姆市。

　　From couch potatoes to Olympic athletes, everyone has a physical capacity for exertion, beyond which the body becomes stressed and begins to feel bad. How much stems from genetic factors─things like lung capacity, oxygen transport and the rate at which oxygen is used in the muscle cells─is still a subject of scholarly debate. Estimates vary from 10% to 50%, says Panteleimon Ekkekakis, a professor of kinesiology at Iowa State who has been studying the psychophysiology of exercise.

　　从宅男到奥运会运动员，每个人都有一个运动的体能极限，超过之后身体就会承受压力，开始感觉不舒服。这个极限有多少来自于遗传因素──如肺活量、氧气输送能力和肌肉细胞耗氧比率等──仍是一个学术研究的课题。爱荷华州立大学运动技能学教授潘特莱姆•艾科卡奇斯(Panteleimon Ekkekakis)一直在研究运动领域的心理生理学，他说遗传因素的影响估计在10%到50%之间。

　　But many sedentary people push beyond their intrinsic range when they try to exercise too quickly or intensely, which can make them hate the activity and want to stop, says Dr. Ekkekakis.

　　艾科卡奇斯教授表示，许多不好动的人一锻炼就采取过于急躁或过于激烈的方式，超过自己固有的体能极限，导致他们讨厌运动，想要放弃。

　　The idea hinges on something called the 'ventilatory threshold.' Normally when people breathe, they expel an amount of carbon dioxide that is equal to the amount of oxygen taken in. But beyond the ventilatory threshold, the release of carbon dioxide begins to exceed the body's intake of oxygen. This excess release of carbon dioxide is a sign that the muscles have become more acidic, which the body finds stressful.

　　问题的关键在于一个名为“通气阀”(ventilatory threshold)的供氧临界点。通常人们呼吸时，呼出的二氧化碳与吸入的氧气大致相当，但超过通气阀后，呼出的二氧化碳开始超过吸入的氧气。二氧化碳的过度释放是一种迹象，表明肌肉已经开始变酸，身体承受的压力变大。

　　For most individuals, the ventilatory threshold is around 50% to 60% of the way to their maximum capacity, though there is tremendous individual variation. For elite athletes, the threshold may be as high as 80%, while sedentary people may hit it at 35%.

　　大多数人的通气阀处于最大供氧能力的50%到60%之间。不过，不同个体之间存在巨大差异，精英运动员的通气阀可以高达80%，而不好动的人可能只有35%。

　　By using tricks such as listening to music, people can continue to feel good even slightly past their ventilatory threshold, Dr. Ekkekakis and his colleagues have found. As people approach their maximum capacity, however, the feel-bad reaction is unavoidable.

　　艾科卡奇斯博士和他的同事发现，通过听音乐等方法，人们甚至可以在轻微超过通气阀后依然觉得身体很舒服。然而，当人体接近供氧最大能力时，出现不舒服的反应是不可避免的。