Question

    What do extreme marathoners, mountain hikers and professional bicycle racers all have in common? They push their bodies to unsustainable (不可持续的) extremes of physical stress.

We tend to think there’s no limit to human physical achievements. But a new study, published in Science Advances, says there is a definite limit to human endurance (耐力). Beyond that, our bodies begin to break down.

To find the limit, a US research team tracked marathon runners over a five-month period, measuring competitors’ initial basal metabolic rates (BMR, 基础新陈代谢率) – the amount of energy they expend when they rest. Then they looked at how many calories(卡路里) each runner burned per day.

The team found that the maximum amount of energy a human can expend is 2.5 times of BMR. It equals 4,000 calories of energy per day. These calories can help a trained athlete to run about 42 kilometers in a day.

But people can’t keep using this amount of calories all the time. “You can do really intense stuff for a couple of days, but if you want to last longer then you have to dial it back,” US evolutionary anthropologist Herman Pontzer told the BBC.

Pontzer explained that the problem is our guts (消化道). “There’s … a limit to how many calories our guts can effectively absorb per day,” he said in the Daily Mail. At that point, the body is burning calories more quickly than it can absorb food and convert (转化) it into energy.

These new findings could help athletes to best work underneath this ceiling. For example, they could manage their daily exercise time based on their BMR, to get enough calories and keep going.

However, Pontzer’s team can’t rule out the possibility of someone breaking this limit. “So I guess it’s a challenge to elite endurance athletes,” said Pontzer. “Science works when you’re proven wrong. Maybe someone will break through that ceiling some day and show us what we’re missing.”

1.What did the US research team find in the new study?

A.One’s endurance can be improved through exercise.

B.A trained athlete can do intense activities for more than a week.

C.The average BMR for athletes is 4,000 calories of energy per day.

D.The energy one can expend is no more than 2.5 times of their BMR per day.

2.What is the main purpose of Paragraph 6?

A.To tell us the problem with our guts.

B.To show how our bodies produce energy.

C.To explain why there is a limit to human endurance.

D.To prove the importance of our guts to physical activities.

3.The new findings could help athletes ______.

A.keep a more balanced diet

B.save time and reduce stress

C.arrange their training properly

D.improve their performance quickly

4.Which of the following would Pontzer probably agree with?

A.It’s possible that someone could break the endurance limit.

B.It’s no good trying to work above the 2.5x endurance ceiling.

C.Further data is needed to make the study’s results more accurate.

D.The 2.5x endurance ceiling is not a problem for many elite athletes.

Answer

1.D

2.C

3.C

4.A

【解析】

本文是说明文。一项新的研究表明，人类的耐力是有明确的极限的，一个人所能消耗的最大能量是基础新陈代谢率的2.5倍。这一发现可以帮助运动员根据基本代谢率来安排每天的训练。

1.细节理解题。根据第四段中“The team found that the maximum amount of energy a human can expend is 2.5 times of BMR.”可知，研究小组发现，一个人所能消耗的最大能量不超过他的基础新陈代谢率的2.5倍。故选D项。

2.推理判断题。第五段提出“people can’t keep using this a mount of calories all the time.”人们摄入卡路里的量是有限的；Pontzer解释原因“the problem is our guts, …There’s … a limit to how many calories our guts can effectively absorb per day.（问题在于肠道……我们的肠道每天有效吸收的卡路里是有限的。）” 第六该段解释了人类的耐力有限的原因是因为肠道每天有效吸收的卡路里有限。故选C项。

此题易错项为A项。此题要求阅读时通过文章所提供的的事实，客观地推测作者的写作意图。该段陈述的事实是“肠道每天有效地吸收卡路里是有限的，而身体燃烧卡路里的速度比它吸收食物和将食物转化为能量的速度要快”。从这些事实中，可以推断出在该段中作者是解释为什么一个人的耐力是有限的。因为该段首句提到了“The problem is ourguts”,此题易误选A项。若选A项是断章取义，没有结合上面几段中的内容“The team found that the maximumamount of energy a human can expend is 2.5 times of BMR.”“But people can't keep using this a mount of calories all thetime.”进行归纳分析。

3.推理判断题。根据第七段中“they could manage their daily exercise time based on their BMR, to get enough calories and keep going.（他们可以根据基本代谢率来安排每天的锻炼时间，以获得足够的卡路里并继续锻炼）”可以推断，新的发现能够帮助运动员在极限下更合理安排自己的训练。故选C项。

4.细节理解题。根据最后一段中“However, Pontzer’s team can’t rule out the possibility of someone breaking this limit.（Pontzer的团队不能排除有人突破这个极限的可能性。）”和最后一句“Maybe someone will break through that ceiling some day”可知，Pontzer 团队认为还是有可能有人会打破这个耐力极限。故选A项。