As we age, even if we’re healthy, the heart just isn’t as efficient in processing oxygen as it used to be. In most people the first signs show up in their 50s or early 60s. And among people who don’t exercise, the changes can start even sooner.

“Think of a rubber band. In the beginning, it is flexible, but put it in a drawer for 20 years and it will become dry and easily broken,” says Dr. Ben Levine, a heart specialist at the University of Texas. That’s what happens to the heart. Fortunately for those in midlife, Levine is finding that even if you haven’t been an enthusiastic exerciser, getting in shape now may help improve your aging heart.

Levine and his research team selected volunteers aged between 45 and 64 who did not exercise much but were otherwise healthy. Participants were randomly divided into two groups. The first group participated in a program of nonaerobic(无氧) exercise—balance training and weight training—three times a week. The second group did high-intensity aerobic exercise under the guidance of a trainer for four or more days a week. After two years, the second group saw remarkable improvements in heart health.

“We took these 50-year-old hearts and turned the clock back to 30-or 35-year-old hearts,” says Levine. “And the reason they got so much stronger and fitter was that their hearts could now fill a lot better and pump(泵送) a lot more blood during exercise.” But the hearts of those who participated in less intense exercise didn’t change, he says.

“The sweet spot in life to start exercising, if you haven’t already, is in late middle age when the heart still has flexibility,” Levine says. “We put healthy 70-year-olds through a yearlong exercise training program, and nothing happened to them at all.”

Dr. Nieca Goldberg, a spokeswoman for the American Heart Association, says Levine’s findings are a great start. But the study was small and needs to be repeated with far larger groups of people to determine exactly which aspects of an exercise routine make the biggest difference.

1.What does Levine want to explain by mentioning the rubber band?

A The right way of exercising.

B The causes of a heart attack.

C The difficulty of keeping fit.

D The aging process of the heart.

解析：选D。D 推理判断题。根据第二段“Think of a rubber band. In the beginning, it is flexible, but put it in a drawer for 20 years and it will become dry and easily broken,...That’s what happens to the heart.” (想想橡皮筋。一开始，它是灵活的，但把它放在抽屉里20年，它就会变得干燥，很容易破碎……这就是心脏的变化。)可知，莱文想通过提到橡皮筋来解释心脏的老化过程，故选D。

2.In which aspect were the two groups different in terms of research design?

A Diet plan.

B Professional background.

C Exercise type.

D Previous physical condition.

解析：选C。C 推理判断题。根据第三段的“The first group participated in a program of nonaerobic exercise— balance training and weight training—three times a week. The second group did high-intensity aerobic exercise under the guidance of a trainer for four or more days a week.”可知，两组在研究设计上的不同在于运动类型的不同，故选C。

3.What does Levine’s research find?

A Middle-aged hearts get younger with aerobic exercise.

B High-intensity exercise is more suitable for the young.

C It is never too late for people to start taking exercise.

D The more exercise we do, the stronger our hearts get.

解析：选A。A 细节理解题。根据第三段的“The second group did high-intensity aerobic exercise under the guidance of a trainer for four or more days a week. After two years, the second group saw remarkable improvements in heart health.” (第二组在教练的指导下每周进行4天或更多的高强度有氧运动。两年后，第二组的心脏健康状况有了显著改善。)和第四段的“‘We took these 50-year-old hearts and turned the clock back to 30-or 35-year-old hearts,’ says Levine.” (莱文说：“我们把这些50岁的心脏的时钟拨回30或35岁的心脏。)可知，莱文的研究发现了通过有氧运动，中年人的心脏会变得更年轻，故选A。

4.What does Dr. Nieca Goldberg suggest?

A Making use of the findings.

B Interviewing the study participants.

C Conducting further research.

D Clarifying the purpose of the study.

解析：选C。C 推理判断题。根据最后一段的“But the study was small and needs to be repeated with far larger groups of people to determine exactly which aspects of an exercise routine make the biggest difference.”可知，妮卡·戈德堡博士建议进行进一步的研究。故选C。