评论
打印
V3：(V 40)
第一段：1922年有个诺贝尔的理论，人劳累，是因为肌肉释放的酸达到极限，从而让肌肉休息。
第二段：加拿大的科学家有异议。而南非的科学家取出反例，在一种特定的情况下(这种情况可以导致肌肉释放的酸不会大幅增加)，对运动员研究发现他们疲劳的时候酸的含量很低，30%的肌肉已经休息了。虽然这些运动员说他们已经很累，达到极限了。
第三段：科学家们就提出假设来解决这个问题，指出1922年有个诺贝尔的理论是部分正确的。但是人的劳累其实不是客观事实，而是人的主观情绪。然后这个理论还能够解释部分现象。
类似原文：By pipilovelail
注意highlight的部分
Interestingly —or unnervingly,depending on how you look at it— some researchers are uncovering evidence thatStanovnik’s rule of thumb might be right. A spate of recent studies hascontributed to growing support for the notion that the origins and controls offatigue lie partly, if not mostly, within the brain and the central nervoussystem. The new research puts fresh weight to the hoary coaching cliché: youonly think you’re tired.From the time of Hippocrates, the limits of humanexertion were thought to reside in the muscles themselves, a hypothesis thatwas established in 1922 with the Nobel Prize-winning work of Dr. A.V. Hill. Thetheory went like this: working muscles, pushed to their limit, accumulatedlactic acid.When concentrations of lactic acid reached a certain level, so theargument went, the muscles could no longer function. Muscles contained an‘‘automatic brake,’’ Hill wrote,‘‘carefully adjusted by nature.’’Researchers,however, have long noted a link between neurological disorders and athleticpotential. In the late 1800’s, the pioneering French doctor Philippe Tissiéobserved that phobias and epilepsy could be beneficial for athletic training. Afew decades later, the German surgeon August Bier measured the spontaneous longjump of a mentally disturbed patient, noting that it compared favorably to theexisting world record. These types of exertions seemed to defy the notion ofbuilt-in muscular limits and, Bier noted, were made possible by‘‘powerfulmental stimuli and the simultaneous elimination of inhibitions.’’Questionsabout the muscle-centered model came up again in 1989 when Canadian researcherspublished the results of an experiment called Operation Everest II, in whichathletes did heavy exercise in altitude chambers. The athletes reachedexhaustion despite the fact that their lactic-acid concentrations remainedcomfortably low. Fatigue, it seemed, might be caused by something else.In 1999,three physiologists from the University of Cape Town Medical School in SouthAfrica took the next step. They worked a group of cyclists to exhaustion duringa 62-mile laboratory ride and measured, via electrodes, the percentage of legmuscles they were using at the fatigue limit. If standard theories were true,they reasoned, the body should recruit more muscle fibers as it approachedexhaustion — a natural compensation for tired, weakening muscles.Instead, theresearchers observed the opposite result. As the riders approached completefatigue, the percentage of active muscle fibers decreased, until they wereusing only about 30 percent. Even as the athletes felt they were giving theirall, the reality was that more of their muscles were at rest.Was the brainpurposely holding back the body?‘‘It was as if the brain was playing a trick onthe body, to save it,’’says Timothy Noakes, head of the Cape Town group. ‘‘Whichmakes a lot of sense, if you think about it. In fatigue, it only feels likewe’re going to die. The actual physiological risks that fatigue represents areessentially trivial.’’From this, Noakes and his colleagues concluded that A.V.Hill had been right about the automatic brake, but wrong about itslocation.They postulated the existence of what they called a central governor:aneural system that monitors carbohydrate stores, the levels of glucose andoxygen in the blood, the rates of heat gain and loss, and work rates. Thegovernor’s job is to hold our bodies safely back from the brink of collapse bycreating painful sensations that we interpret as unendurable musclefatigue.Fatigue, the researchers argue, is less an objective event than asubjective emotion —the brain’s clever, self-interested attempt to scare youinto stopping.The way past fatigue, then, is to return the favor: to fool thebrain by lying to it, distracting it or even provoking it. (That said, mentalgamesmanship can never overcome a basic lack of fitness. As Noakes says, thebody always holds veto power.)‘‘Athletes and coaches already do a lot of thisinstinctively,’’Noakes says.‘‘What is a coach, after all, but a technique forovercoming the governor?’’The governor theory is far from conclusive, but somescientists are focusing on a walnut-size area in the front portion of the braincalled the anterior cingulate cortex. This has been linked to a host of corefunctions, including handling pain, creating emotion and playing a key role inwhat’s known loosely as willpower. Sir Francis Crick, the co-discoverer of DNA,thought the anterior cingulate cortex to be the seat of the soul. In the sportsworld, perhaps no soul relies on it more than Jure Robic’s.Some people‘‘havethe ability to reprocess the pain signal,’’ says Daniel Galper, a seniorresearcher in the psychiatry department at the University of Texas SouthwesternMedical Center at Dallas. ‘‘It’s not that they don’t feel the pain; they justshift their brain dynamics and alter their perception of reality so the painmatters less. It’s basically a purposeful hallucination.’’Noakes and hiscolleagues speculate that the central governor theory holds the potential toexplain not just feats of stamina but also their opposite: chronic fatiguesyndrome (a malfunctioning, overactive governor, in this view).Moreover, thegovernor theory makes evolutionary sense. Animals whose brains safeguarded anemergency stash of physical reserves might well have survived at a higher ratethan animals that could drain their fuel tanks at will.The theory would alsoseem to explain a sports landscape in which ultra-endurance events have gonefrom being considered medically hazardous to something perilously close toroutine. The Ironman triathlon in Hawaii —a 2.4-mile swim, 112-mile bike rideand marathon-length run—was the ne plus ultra in endurance in the 1980’s, buthas now been topped by the Ultraman, which is more than twice as long. Onceobscure, the genre known as adventure racing, which includes 500-plus-milewilderness races like Primal Quest, has grown to more than 400 events eachyear. Ultramarathoners, defined as those who participate in running eventsexceeding the official marathon distance of 26.2 miles, now number some 15,000in the United States alone. The underlying physics have not changed, but ratherour sense of possibility. Athletic culture, like Robic, has discovered a way totweak its collective governor.
