古力娜扎偶像来了身高:请朋友们帮忙翻译一下，谢谢

Running for Your Life
A Harvard study links exercise with longevity
The hordes of American who roll out of bed, slip into their Reeboks and run for an hour in the face of snarling dogs, potential muggers and hordes of Americans heading in the opposite direction on their Schwinn 10-speeds must wonder sometimes whether it’s worth the aggravation after all , if a rash of recent books and articles like “The Exercise Myth” can be believed, the evidence that physical activity leads to a longer and healthier life is based on a flawed interpretation of cause and effect. It isn’t that exercise prolongs life, the argument goes, it’s just that people who engage in sports and active occupations are healthier in the first place. But the fitness buffs should not put their rowing machines in dry dock just yet. According to a long-term study involving nearly 17000 loyal sons of Harvard, it now seems that athletic effort is far from a waste of time. Moderate exercise, said a report in last week’s New England Journal of medicine, can add up to two years to a person’s life.
In the mid-1960s Dr. Ralph S. Paffenbarger Jr. and his colleagues at the Stanford University School of Medicine recruited the Harvard graduates, 35 to 74, and asked them oto answer detailed questionnaires about their general health and living habits. Follow-ups carried out until 1978 showed that men who expended at least 2000 calories per week through exercise had mortality rates one-quarter to one-third lower than those burning up fewer calories. The life-prolonging level of activity cited in the report is the equivalent of five hours of brisk walking, about four hours of jogging or a shade more than three hours of squash. More exercise meant a better chance at a long life –up to a point. A regimen that burned more than 3500 calories tended to cause injuries that negated most of the benefits derived from exercise.