新视野大学英语读写教程听力 第三册 te-unit02-b

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[00:00.00]，就把hxen.com复制到QQ个人资料中！Does Exercise Have Unexpected Benefits?
[00:-1.00]1  Just as exercise strengthens the heart and lungs,
[00:-2.00]bones and muscles, it may also power up the brain.
[00:-3.00]A succession of scientific studies of animals
[00:-4.00]implies that physical activity has a positive effect on mental functioning.
[00:-5.00]2  "It\'s clear that the brain benefits from exercise,"
[00:-6.00]says brain scientist William Greenough
[00:-7.00]of the University of Illinois at Urbana-Champaign.
[00:-8.00]His studies with rats have demonstrated two primary effects of activity:
[00:-9.00]vigorous physical exercise provides the brain with more fuel,
[00:10.00]and skill-based exercise increases the formation of connections in the brain,
[00:11.00]which, according to the proposals of some scientists,
[00:12.00]may make the brain better able to process information.
[00:13.00]3  In one experiment,
[00:14.00]laboratory rats were separated into three groups.
[00:15.00]One group was exercised by running inside an automatic wheel,
[00:16.00]a second group improved their skills in a complicated obstacle course,
[00:17.00]and a third group was inactive.
[00:18.00]4  "The animals that learned to go through
[00:19.00]the obstacle course exhibited a greater number of brain connections
[00:20.00]than the animals in the exercised or inactive groups,"
[00:21.00]Greenough said. "In contrast,
[00:22.00]the animals that exercised inside the automatic wheel
[00:23.00]possessed a greater density of blood vessels in the brain
[00:24.00]than did either of the other two groups of animals."
[00:25.00]5  Learning a new dance step may boost the brain
[00:26.00]in the same way that learning a language can,
[00:27.00]he says. And if the dance is a good physical exercise as well,
[00:28.00]the benefits multiply.
[00:29.00]Young brains may be especially able to boost brain power through exercise,
[00:30.00]suggested another of Greenough\'s experiments
[00:31.00]that showed the most significant changes in the brain
[00:32.00]occurred among rats that had been exercised when very young.
[00:33.00]And while animals aren\'t people,
[00:34.00]he says it is logical to make the inference
[00:35.00]that an effect found in rats may also apply to humans.
[00:36.00]6  Human studies have focused primarily on older adults
[00:37.00]and suggest that regular exercise
[00:38.00]can improve the speed with which the brain processes information.
[00:39.00]Measurements made by Arthur Kramer at the University of Illinois
[00:40.00]demonstrated that inactive adults,
[00:41.00]aged 63 to 82, could hit buttons faster in response to a tone
[00:42.00]after they went through a 10-week water exercise course.
[00:43.00]A corresponding control group that didn\'t exercise showed no improvement.
[00:44.00]7  This boost in reaction time after exercise training
[00:45.00]may occur because declines associated with getting old could
[00:46.00]actuallly stem from declines in physical condition.
[00:47.00]Some scientists speculate the reduction in mental function
[00:48.00]often attributed to getting old
[00:49.00]may really be a penally of neglecting to stay physically active,
[00:50.00]in addition to related factors such as medicines and poor diet.
[00:51.00]8  "In older people,
[00:52.00]an exercise program appears important for brain maintenance,"
[00:53.00]says Daniel M.Landers,
[00:54.00]professor of exercise science at Arizona State University,
[00:55.00]who recently published an article
[00:56.00]reviewing the scientific literature on activity\'s effect on the brain.
[00:57.00]Numerous studies show that children who engage in regular physical activity
[00:58.00]do better in school than their inactive classmates.
[00:59.00]But until recently,
[-1:00.00]the academic edge gained by participating in sports
[-1:-1.00]was thought to come from the increased self-confidence,
[-1:-2.00]the better mood,
[-1:-3.00]and the ability to concentrate that comes from burning off steam in exercise.

[-1:-4.00]Now, however,
[-1:-5.00]some scientists have revised their way of thinking,
[-1:-6.00]and point to possible physical connections.
[-1:-7.00]10  Pierce J.Howard, another expert,
[-1:-8.00]says new research indicates that physical exercise
[-1:-9.00]increases the amount of certain brain
[-1:10.00]chemicals that stimulate growth of nerve cells.
[-1:11.00]Consequently, the brains of people who exercise
[-1:12.00]may be better equipped to tackle mental challenges.
[-1:13.00]11  Inactivity may also have negative effects on mind and body alike.
[-1:14.00]"Scientists recognize that mind is body,
[-1:15.00]and body is mind," comments Howard.
[-1:16.00]The most beneficial forms of exercise, he says, engage both.

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