VOA慢速英语2012 SCIENCE IN THE NEWS - How Much Exercise Do You Really Need?

（单词翻译）

SCIENCE IN THE NEWS - How Much Exercise Do You Really Need?

BOB DOUGHTY¹: This is the VOA Special English program SCIENCE IN THE NEWS. I’m Bob Doughty.

SHIRLEY GRIFFITH: And I’m Shirley Griffith. Today, we will tell why exercise is so important. And we will tell about some popular ways to get in good shape.

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BOB DOUGHTY: Health experts have long noted² the importance of physical activity. Exercise not only improves your appearance. It can also improve your health. Exercise helps to reduce the risk of some diseases. They include heart disease, stroke, type-two diabetes³, osteoporosis and even some kinds of cancer.

America’s Centers for Disease Control and Prevention says heart disease is the leading cause of death in the United States. In two thousand nine, heart disease killed almost six hundred thousand Americans. High blood pressure and high cholesterol⁴ levels in blood can increase your risk of heart disease. Medical experts say both can be reduced through normal exercise.

SHIRLEY GRIFFITH: Physical activity is also known to increase the release of endorphins. These chemicals reduce feelings of pain. They also help people feel more happy and peaceful. There is some debate about exactly what causes the brain to release endorphins. Some experts believe it is the act of exercising itself. Others say it is the feeling one gets from having met an exercise goal. Either way, the two things work together when it comes to improving one’s emotional health.

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BOB DOUGHTY: Exercise improves your energy levels by increasing the flow of blood to the heart and blood vessels⁵. One of the main reasons people exercise is to control or reduce their weight. Physical activity burns calories – the energy stored in food. The more calories you burn, the easier it is to control or reduce your weight.

So exactly how much exercise do you need to do to gain all of these great health effects? Experts say it is easier than you think.

In two thousand eight, the Centers for Disease Control released its first ever Physical Activity Guidelines⁶ for Americans. The report included suggestions for young people, adults, disabled persons and those with long-term health problems. One of the major ideas noted in the report was that some activity is better than none. So if you are not doing anything, now is the time to get started.

SHIRLEY GRIFFITH: The CDC defines⁷ physical activity as anything that gets your body moving. And, it says there are two separate, but equally important kinds of physical activity. Aerobic⁸ or cardio exercise gets your heart rate going faster and increases your breathing. Some examples are activities like walking at an increased speed, dancing, swimming or riding a bicycle.

Muscle-strengthening activities help build and strengthen muscle groups in the body. This kind of exercise includes lifting weights, or doing sit-ups and push-ups.

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BOB DOUGHTY: To get the most from your exercise plan, experts say adults should get at least two and a half hours of aerobic exercise each week. More intense activities reduce the suggested amount of time to one hour and fifteen minutes. Some examples are playing basketball, swimming and distance running.

Earlier advice from the CDC said people need to exercise thirty minutes each day for at least five days to get the health benefits of exercise. More recent research suggested that those gains are the same whether you exercise for short periods over five days or longer sessions over two or three days.

In addition, the newer suggestions say any exercise plan should include at least two days of muscle training. Each exercise period should be at least ten minutes long. The total amount of activity should be spread over at least two days throughout the week. Most importantly, experts say people should choose physical activities that they find fun. This helps to guarantee that they stay with the program.

SHIRLEY GRIFFITH: So, what are some of the most popular forms of exercise in the United States? Walking tops the list. A two thousand six report from the CDC found that more than seventy-nine million Americans walk to stay physically⁹ fit. For many people, it is considered the easiest way to get exercise. It does not require a health club membership¹⁰. Walking is safe. And, it is said be to as valuable for one’s health as more intense forms of exercise like jogging.

Walking is also said to be less damaging to the knees and feet. This makes it a better choice of exercise for older adults.

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BOB DOUGHTY: Another popular form of exercise is jogging, or running at a slow to medium speed. USA Track and Field Hall of Famer, Bill Bowerman, was credited with bringing jogging to the United States in the nineteen seventies. He did so after witnessing the popularity¹¹ of the activity himself during a trip to New Zealand in the nineteen sixties. He started the first running club in America and wrote a book about jogging for fitness¹². Bill Bowerman also helped establish Nike, the tennis shoe company.

Jogging provides great physical conditioning for the heart and lungs. And, it increases the flow of blood and oxygen in the body. All of these things combined help to improve heart activity, lower blood pressure and cholesterol levels, and reduce bone and muscle loss. Running is also a good way to lose weight. People burn an average of one hundred sixty calories a kilometer while running.

SHIRLEY GRIFFITH: The Census¹³ Bureau says swimming was the second most popular sports activity in the United States in two thousand eight. The top activity was exercise walking. Swimming is said to be one of the best ways to exercise. Nearly all of the major muscle groups are put to work.

Swimming also presents less risk of muscle and joint¹⁴ injury because of the body’s weightlessness in water. This makes it a great choice of exercise for people with special needs, like pregnant¹⁵ women, older adults, and persons who are overweight.

Some people have questioned whether swimming burns as many calories as other forms of exercise. But one thing is sure: the effects on your health are just as great.

Water aerobics¹⁶ is another popular form of exercise. This can be anything from walking or running against the resistance of water, to doing jumping jacks¹⁷ in the water.

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BOB DOUGHTY: Dancing can also be a fun way to exercise. This is especially true for those who see exercise as a necessary evil: something they should do, not something they want to do.

A dance-fitness program called Zumba has grown in popularity in recent years. Zumba is said to be one of the fastest-growing group programs in the physical fitness industry today.

Alberto Beto Perez created Zumba in his native Colombia in the nineteen nineties. His dance-fitness program is based on salsa, meringue, and other forms of Latin American music. Mister Perez brought the program to the United States in two thousand one. Since then it has spread around the world.

The Zumba website says its classes are now offered in more than one hundred thousand gyms, fitness studios and dance clubs around the world. That is up from about two thousand locations in two thousand six. The website also says that more than twelve million people now attend Zumba classes in one hundred twenty-five countries.

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SHIRLEY GRIFFITH: Whatever kind of exercise you choose, experts agree that you should start small and work your way up. Start by exercising ten minutes a day two times a week. After a few weeks, increase your time to fifteen or twenty minutes, and increase the number of days.

Next, aim to increase the intensity¹⁸ of your workout. If you have been walking, trying walking faster, or take turns between walking and jogging. And try not to forget those muscle strengthening exercises. The more time you spend exercising, the more health benefits you get.

Health experts advise people who have been physically inactive to have a complete physical exam before beginning a new exercise program. If one of the goals of your exercise program is to lose weight, you will also need to change how and what you eat. Next week we will look at the influence of diet on your weight loss efforts.

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BOB DOUGHTY: This SCIENCE IN THE NEWS was written and produced by June Simms. I’m Bob Doughty.

SHIRLEY GRIFFITH: And I’m Shirley Griffith. Join us next week for more news about science in Special English on the Voice of America.