越度考古 Lactic acid

joyous314

刚刚看了一下越度狗，然后发现了acid那道题，一战是在519，当月越度狗里也有这道题并且是自己总结的，一片文，几道题，没想到这次又有，such a surprise！！九月二战希望有个好成绩..大家一起加油嘞~


1.1.2
Lactic acid *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，不是这样，加拿大的科学家有异议，因为加拿大的研究人员发现在海拔高的地方运动员感觉疲劳， 但那个acid并不多。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，1922年有个诺贝尔的理论是部分正确的，肌肉fatigue不一定是acid的原因（也有acid的原因），有可能是大脑控制各种resource发现你要不行了，然后就给你个信号说你不行了，但是其实你还是行的，说其实Fatigue其实是一种大脑主观的保护机制，来防止肌肉运行过度，而且这个解释可以解释老的理论和新的发现其实并不矛盾。
1、最后一段说其实第一段的那个theory不是完全的错，但是真正决定什么时候stopthe muscle function的是neural system。所以这个过程是subjective而不是Objective(有道题问了这个)。
2、问第二段作者提cannada那个研究有什么作用
3、问题考了一个是最后一段的作用 给第二段的现象一个科学模型？总结了前面
4、问题，main idea。如果人要控制疲劳那么应该怎么做？训练自己，让自己对疲劳没感觉。
5、以总结题为主
6、第2段澳大利亚科学家说得第一段的内容不对暗示着神马，然后选项有说是神马肌肉导致了疲劳等
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 beright. A spate of recent studies has contributed to  growing support for the notion that theorigins and controls of  fatigue liepartly, if not mostly, within the brain and the central  nervous system. The new research puts freshweight to the hoary  coaching cliché: youonly think you’re tired.Fromthe time of Hippocrates, the limits of human exertion were  thought to reside in the muscles themselves,a hypothesis that was  established in1922 with the Nobel Prize-winning work of Dr. A.V.  Hill. The theory went like this: workingmuscles, pushed to their  limit,accumulated lactic acid.When concentrations of lactic acid  reached a certain level, so the argumentwent, the muscles could no  longerfunction. Muscles contained an ‘‘automatic brake,’’  Hill wrote,‘‘carefully adjusted bynature.’’Researchers, however, have long noted a link between neurological  disorders and athletic potential. In the late1800’s, the pioneering  French doctor Philippe Tissié observed thatphobias and epilepsy  could be beneficialfor athletic training. A few decades later, the German surgeon August Bier measured the spontaneous long jump of a  mentally disturbed patient, noting that itcompared favorably to the  existing worldrecord. These types of exertions seemed to defy the  notion of built-in muscular limits and, Biernoted, were made  possible by‘‘powerfulmental stimuli and the simultaneous elimination of inhibitions.’’Questions about the muscle-centered model came up again in 1989when  Canadian researchers published theresults of an experiment called Operation Everest II, in which athletes did heavy exercise in  altitude chambers. The athletes reachedexhaustion despite the fact  that theirlactic-acid concentrations remained comfortably low.  Fatigue, it seemed, might be caused bysomething else.In 1999, three physiologists from the University of Cape TownMedical  School in South Africa
took the next step.They worked a group of  cyclists to exhaustionduring a 62-mile laboratory ride and measured, via electrodes, the percentage of leg muscles they were using atthe  fatigue limit. If standard theorieswere true, they reasoned, the  bodyshould recruit more muscle fibers as it approached exhaustion —  a natural compensation for tired, weakeningmuscles.Instead, the researchers observed the opposite result. As the riders  approached complete fatigue, the percentageof active muscle fibers  decreased, untilthey were using only about 30 percent. Even as the  athletes felt they were giving their all, thereality was that more  of their muscleswere at rest.Was the brain purposely holding back  the body?‘‘It was as if the brain was playinga trick on the body, to save  it,’’saysTimothy Noakes, head of the Cape Towngroup.  ‘‘Which makes a lot of sense, ifyou think about it. In fatigue,  it onlyfeels like we’re going to die. The actual physiological  risks that fatigue represents are essentiallytrivial.’’From this,Noakes and his colleagues concluded that A.V. Hill had  been right about the automatic brake, butwrong about its location.They postulated the existence of what they called acentral governor:a neural system that monitors carbohydrate stores, thelevels of  glucose and oxygen in theblood, the rates of heat gain and loss, and work rates. The governor’s job is to hold our bodies safely back  from the brink of collapse by creatingpainful sensations that we  interpret asunendurable muscle fatigue.Fatigue,the researchers argue, is less an objective event than a  subjective emotion —the brain’s clever,self-interested attempt  to scare youinto stopping.The way past fatigue, then, is to return  the favor: to fool the brain by lying to it,distracting it or even  provoking it.(That said, mental gamesmanship can never overcome a  basic lack of fitness. As Noakes says, thebody always holds veto  power.)‘‘Athletesand coaches already do a lot of this instinctively,’’Noakes says.‘‘What is a coach, after all,  but a technique for overcoming the governor?’’Thegovernor theory is far from conclusive, but some scientists are  focusing on a walnut-size area in the frontportion of the brain  called the anteriorcingulate cortex. This has been linked to a host  of core functions, including handling pain,creating emotion and  playing a key rolein what’s known loosely as willpower. Sir Francis  Crick, the co-discoverer of DNA, thought theanterior cingulate  cortex to be the seatof the soul. In the sports world, perhaps no soul relies on it more than Jure Robic’s.Some people‘‘have the abilityto reprocess the pain signal,’’  saysDaniel Galper, a senior researcher in the psychiatry department  at the University of Texas SouthwesternMedical Center at Dallas.  ‘‘It’s not that they don’t feel the pain; theyjust shift  their brain dynamics andalter their perception of reality so the pain matters less. It’s basically a purposeful hallucination.’’Noakes and his colleaguesspeculate that the central governor theory holds the potential to explain not just feats of stamina but also  their opposite: chronic fatigue syndrome (amalfunctioning,  overactive governor, inthis view).Moreover, the governor theory makes evolutionary sense. Animals whose brains safeguarded an  emergency stash of physical reserves mightwell have survived at a  higher rate thananimals that could drain their fuel tanks at will.The theory would also seem toexplain a sports landscape in which ultra-endurance events have gone from being considered medically  hazardous to something perilously close toroutine. The Ironman  triathlon in Hawaii —a 2.4-mile swim,112-mile bike ride and  marathon-lengthrun—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. Once obscure, the genre knownas adventure racing,  which includes500-plus-mile wilderness races like Primal Quest, has  grown to more than 400 events each year.Ultramarathoners, defined as  those whoparticipate in running events exceeding the official  marathon distance of 26.2 miles, now numbersome 15,000 in theUnited  Statesalone. The underlying physics have not changed, but rather our  sense of possibility. Athletic culture, likeRobic, has discovered a  way to tweak itscollective governor.

wulanjie123

好给力~~~~~~~~~这算认领了吧？

cutie0829

ding

xyc19901015

这个月阅读怎么那么多考古啊。。。

starry1007

这个月阅读怎么那么多考古啊。。。

-- by 会员 xyc19901015 (2011/8/23 16:44:17)

这是好事啊！谢谢lz劳动成果！

Edwardsyh

LZ强大！！！！

pangbo629

多谢lz

angealwang

不会吧~~我524一战的~9月份要二战了~又是这篇？？！！！