Most of the suggestions about exercise are pretty clear— do something—anything—to get moving. Any activity is better than no activity, so simply letting the body move is what's important. And there's a good reason for the simplicity of that message—with one third of Americans not exercising at all, the easier the advice, the better

   But for those who follow those suggestions and get regular exercise, things could be a little more difficult to deal with. How far is too far when it comes to pushing your body? Overdoing exercise can lead to injuries, and may end up removing all the benefits physical activity can have.

   Our bodies are trained to adapt, so even if you run or bike every day, at a certain point, your body starts to coast. Your muscles don't work as hard, your heart doesn't beat as quickly, and you don't breathe as heavily to pump oxygen to your cells. "When you hit a plateau (稳定状态), it is your body getting used to an activity. You have achieved your body's potential for that activity." says Scott Danberg, Director of Fitness. "If you keep working at the same activity, it's impossible sometimes to keep moving up. It means you are still in great shape, but you have to start changing things to move forward."

   So how do you make sure that your exercise continues to work for you? Some fitness trainers recommend changing workouts every four to six weeks to strengthen the body. Others say that the best test is whether your workout challenges you—if you're breathing hard and feel tired after exercising, then you're harvesting the benefits of that workout, whatever it might be.

   And how do you know if you're pushing too hard? While putting some stress on the body is required to improve fitness, Barbara Bushman, a professor at Missouri State University, says exercise overload can cause injury. "Typically for beginners, gradual increases in duration (期间) are recommended until the person is comfortable with longer exercise duration. Then the duration might be cut back a bit but the stress increased. The idea is not to increase all areas at once," she says.

   Figuring out when to push and when to pull back isn't an exact science. Genes, for example, influence metabolic rates(代谢速率)and body types, both of which contribute to fitness. One of the best ways to find the most effective exercise plan for you—suited to your body type and your fitness goals—is to regularly step back. A doctor or trainer can help, or you can try the assessments (评估)from the American College of Sports Medicine (ACSM). A good check-in should include your heart rate and body composition. Tracking these measures while you exercise will not only tell you how far you have progressed, but let you know if you've either hit a plateau or are overdoing the workouts.

Our risk of cancer rises sharply as we age. So it makes sense that the elderly should be routinely screened for new tumors(肿瘤)—or doesn’t it?

While such vigilant(警觉的) tracking of cancer is a good thing in general, researchers are increasingly questioning whether all of this testing is necessary for the elderly. With the percentage of people over 65 expected to nearly double by 2050, it’s important to consider the health benefits of screening against the risks and costs of routine testing.

In many cases, screening can lead to surgeries to remove cancer, while the cancers themselves may be slow-growing and may not have serious health problems in patients’ remaining years. But he message that everyone must screen for cancer has become so deep-rooted that when health care experts recommended that women under 50 and over 74 stop screening for breast cancer, it caused a fierce reaction among doctors, patients and groups who are in favor of the screening.

It’s hard to remove deeply held beliefs about cancer screening with scientific data. Certainly, there are people over age 75 who have had cancers detected by routine screening, and gained several extra years of life because of treatment. And clearly, people over age 75 who have other risk factors for cancer, such as a family history or formerly personal experience with the disease, should continue to get screened regularly. But for the remainder, the risk of cancer, while increased at the end of life, must be balanced with other factors like remaining life expectancy(预期寿命).

A recent study suggests that doctors start to make more objective decisions about who will truly benefit from screening—especially considering the explosion of the elderly that will soon increase in our population.

It’s not an easy calculation to make, but one that makes sense for all patients. Dr. Otis Brawley said, “Many doctors are ordering screening tests purely to cover themselves. We need to think about the reasonable use of health care.”

That means making some difficult decisions with elderly patients, and going against the misguided belief that when it comes to health care, more is always better.

Did you ever look up at the moon and think you saw a man’s face there? When the moon is round and full, the shadows(影子) of the moon mountains and the lines of the moon valleys sometimes seem to show a giant nose and mouth and eyes. At least, some people think so.

　　If there were a man on the moon—instead of mountains and valleys that just look like the face of a man—what would he be like?

　　He would not be like anyone you know. He would not be like anyone anybody knows.

　　If the man on the moon were bothered by too much heat or cold the way Earth people are, he could not stay on the moon.

　　The moon becomes very, very hot. It becomes as hot as boiling water. And the moon becomes very, very cold. It becomes colder than ice.

　　Whatever part of the moon the sun shines on is hot and bright. The rest of the moon is cold and dark.

　　If the man on the moon had to breathe to stay alive, he couldn’t live on the moon because there’s no air there. He’d have to carry an oxygen tank, as astronauts do. There’s no food on the moon, either. Nothing grows—not even weeds（grass）.

　　If the man on the moon liked to climb mountains, he would be very happy. There are many high places there, such as the raised land around the holes, or craters(火山口), of the moon. Some of these rims are as tall as Earth’s highest mountains.

　　But if the man on the moon liked to swim, he would be unhappy. There is no water on the moon—just dust and rock.

　　When you think of what it’s like on the moon, you may wonder why it interests our scientists. One reason is that the moon is Earth’s nearest neighbor—it is the easiest place in space to get to.

　　Going back and forth between the moon and Earth, astronauts will get a lot of practice in space travel. Things learned on moon trips will be of great help to astronauts who later take long, long trips to some of the planets.

　　Scientists are also interested in the moon because it has no air. The air that surrounds Earth cuts down the view of the scientists who look at the stars through telescopes. A telescope on the moon would give them a clearer, closer view of the stars.

D

People born in winter are more likely to suffer mental health disorders, according to a recent study carried out by researchers at Vanderbilt University in Tennessee.
Researchers raised baby mice from birth to weaning (断奶) in either “summer” light cycles of 16 hours of light and 8 hours of dark or “winter” cycles of 8 hours of light and 16 hours of dark. A third group experienced 12 hours of light and 12 hours of dark a day.
Then half the winter mice stayed in a winter cycle, while half switched to a summer schedule. The summer mice were similarly split. The mice raised in equal periods of light and dark were split into three groups, one of which stayed on the 12­hour schedule, one of which joined the winter group, and one of which joined the summer group.
After 28 days, it turns out the summer­born mice behaved the same whether they stayed on the summer cycle or switched to winter. But among the winter­born mice, those stayed in winter kept their previous schedule, while those that switched to summer stayed active for an extra hour and a half, which indicates that mice born and weaned in a winter light cycle showed dramatic disruptions in their biological clocks.
The finding is the first of its kind in mammals, and it could explain why people born in winter are at higher risk for mental health disorders including bipolar depression, schizophrenia and seasonal affective disorder.
“We know that the biological clock regulates mood in humans，”said study researcher McMahon. “If the mechanism (机制) similar to the one that we found in mice operates in humans, then it could not only have an effect on a number of behavioral disorders, but also have a more general effect on personality.”

Everyone needs water and a diet  (1)  healthy foods. These foods should  (2)  some fat, some fiber, a little salt and so on.

   People need energy to live. They eat all kinds of foods   (3)   change into energy. Our bodies use different  (4)  of energy. The energy is measured in calories(卡路里). The more  (5)  we take, the more calories we burn.  Even when you are  (6)  , you are using energy---about 65 calories an hour. While you are at school, or walking home, your body is  (7)  up 100 calories an hour. When playing football or basketball, you might be using 400 calories an hour. On   (8)  Day, during the relay race, you will use most of all, perhaps as   (9)  as 650 calories an hour.

   The Chinese diet is considered to be the healthiest in the world.  It contains a lot of fruit and green vegetables. It is  (10)  in fiber and low in sugar and fat. The Chinese eat less sugar than many   (11)  countries in the world. That is  (12)  lots of people in China have white teeth.

   People in the Western world do not eat  (13)  healthy foods. They eat too much fat and sugar and don’t take  (14)  exercise. Because of this, they  (15)  very easily. In order to  (16)   with the quick pace(步伐) of their life and work, they eat a lot of fast food. They eat a lot of sweets, soft drinks, potato crisps, chocolate, butter and ice cream and so on,  (17)  are called  (18)  food by some epicureans（美食家）. The result is that many of them become fat. In order to avoid  (19)   fat and  (20)  ​ it is advisable(明智的) to eat a balanced diet and not eat too many foods that have a high calorie rating.

C

The World Health Organization(WHO) said that processed meat be carcinogenic(致癌). Do you still dare eat cancer-linked processed(加工过的) meat? Here are some comments on the website.

    Bill (Australia) I’d rather live a short, pleasant life than a long, unhappy one, denying(拒绝给予) myself tasty food just because some experts say it’s not healthy. We should all enjoy the one life we have—if I had listened to every piece of health advice I would never go anywhere, eat anything or enjoy life in any way. So, I won’t change my habit. I am going to have a bacon sandwich, glass of wine, burger, can of coke whenever I feel like it.

Tim (America) Is meat really as bad as smoking? I don’t think so. According to the WHO 34,000 people die worldwide per year because they eat processed meat. In 2012, 8.2 million people died of cancer worldwide. That means if you eat a lot of processed meat you have a chance of being among the 0.41 percent of people dying of cancer because of processed meat. I’ll take the chance.

Helen (Switzerland) The WHO doesn’t say that just one bite of meat causes cancer, it is rather saying that people should vary their diet. People who eat more meat often have other unhealthy habits. They usually eat fewer fruits and vegetables and they also often exercise less.

Van (China) Perhaps this report will make people consider becoming vegetarians(素食者). So for your health, the environment and future generations, it is not difficult; it just needs a change of attitude. There is a vast variety of other delicious food available to enjoy.

We find different kinds of animals in the world. Some animals, such as tigers and lions live in big forest and they are called  (1)  animals. Some others like sheep and dogs are  (2)  by men and they are called domestic(驯养) animals. These animals are very different from one another, but we can  (3)  them into big groups: those that eat other animals and those that eat grass and leaves. Animals like the  (4)  belong to the first group.

       Animals are  (5)  great uses to human beings. Men  (6)  wild animals for their fur and meat. Domestic animals are  (7)  more important to men. Without them, life will be  (8)  . People make use of animals in many  (9)  .

       Cows and dogs are useful to men’s  (10)  . They give 80% of the  (11)  men eat every year. Skin of some animals can be  (12)  into expensive overcoats and shoes, which are warm and comfortable and  (13)  a long time. They are very welcome in  (14)  countries. Wool, which is now one of the most important material for textile(纺织)  (15)  , comes from a special kind of  (16)  . From cows, we get milk. And we shouldn’t  (17)  that some domestic animals are kept for transport. Many people  (18)  ride horses. Arabs ride on camels which travel in deserts for days without  (19)  . In some places animals are still used to plough field.  (20)  is clear that men just can’t live without these animals.

    Back in 1969，it was the Apollo 11 crew who flew to the moon in a spaceship．When U.S. astronauts Neil Armstrong and Edwin “Buzz” Aldrin stepped foot on the moon，they were the first．Meanwhile，their fellow astronaut Michael Collins circled the moon in their spaceship，named Columbia．

     When Armstrong and Aldrin were done with their walk，they returned to the command module，and back to Earth．That part of the spaceship is on view at the Smithsonian’s Air and Space Museum in Washington，D.C. But，if you cannot get to Washington，soon you will be able to see Columbia on your computer or your smartphone．

     Digital scientists are scanning the inside of the spaceship．They are creating an online model，in three dimensions，or “3D”．By looking at these photographs，you will be able to see outer space，the way the astronauts did．It will be like sitting in their seats．

Want your very own Columbia spaceship? You will be able to print a 3D copy of Columbia．Experts say anyone can make a life-sized model．But they expect most people to make smaller models of the 320×400cm(11’×13’)command module．

     Scientists are using special 3D technology to scan the inside．They use cameras on long arms to take the photographs．The thousands of photographs taken will be combined with 50 laser scans．

     What would it be like to sit inside Columbia and take a look around? All the images will be loaded into software that allows you to look around the module on a computer screen．The user will be able to see the Columbia both inside and out．The Smithsonian says that the 3D technology gives the user ways to see things they cannot see at the museum．And it will give information that even the museum curators(馆长)have not seen before．

   “With the Command Module，no one has been inside since it came into the collection，” says Adam Metallo，Smithsonian 3D imaging specialist．“Now the information we capture can give anyone in the world a view of what it looks like inside this incredible piece of history．”

  阅读下面短文，从短文后各题所给的四个选项(A、B、C和D)中，选出可以填入空白处的最佳选项。

    People have enjoyed the benefits of cycling in Amsterdam for years. It is a ____  (1)  ____ city for cycling because it is fiat and so is convenient for bikes. There are also plenty of places for bicycle parking and most streets in the city centre have a bicycle ____  (2)  ____. Today some people call Amsterdam the "City of Bicycles: because it's convenient for people to ____  (3)  ____ there."

    In the 1960s, a group of cycling ____  (4)  ____ had an idea. They believed that it would be better for everybody if cars weren't ____  (5)  ____ in the city centre and only bicycles were. They were ____  (6)  ____ that this would help to save energy, ____  (7)  ____ pollution and provide free public transport. The group painted hundreds of bicycles white and ____  (8)  ____ them in lots of neighborhoods around Amsterdam for people to use. Anyone was allowed to ____  (9)  ____ them and use them for short journeys. When someone finished a journey they would ____  (10)  ____ the bike there for someone ____  (11)  ____ to use. The problem was that it didn't ____  (12)  ____ — thieves took all the bicycles within weeks!

    However, more than thirty years later, the "white bike" is ____  (13)  ____ in town this time with a computer chip to record its every ____  (14)  ____! To take a bicycle, you have to ____  (15)  ____ a special card inside. The new "white bike" is not actually white but is an unusual design with bright colors. The bikes are parked at special parking place that has enough ____  (16)  ____. There is already ____  (17)  ____ traffic in central Amsterdam, because both ____  (18)  ____ and tourists have used the white bikes. Indeed, ____  (19)  ____ the good ideas of lots of people, like the cycling fans in the 1960, many people around the world have been ____  (20)  ____ city centre streets without cars for many years.

    As a recipe for losing weight, taking a slice of chocolate cake at breakfast would seem an unlikely fantasy.

    A team from Tel Aviv University found that eating pudding as part of a balanced 600-calorie breakfast that also included proteins and carbohydrates (碳水化合物), could help dieter to lose more weight---and keep it off in the long run.

    Attempting to avoid sweets entirely can create a psychological addiction to these same foods in the long term. So adding desserts to breakfast can control craving(渴望) throughout the rest of the day.

    Over the course of a 32-week-long study, participants, who added desserts to their breakfast lost about 40 pounds more than a group that avoided such foods. What’s more, they kept off the pounds longer.

    A meal in the morning provides energy for the day’s tasks, aids in brain functioning, and kick-starts the body’s metabolism (新陈代谢), making it decisive to weight loss and maintenance. And breakfast is the meal that most successfully regulates ghrelin(胃饥饿素）, the hormone that increases longer. While the level of ghrelin rises before every meals, it is controlled most effectively at breakfast time.

    The researchers hoped to determine whether meal time and composition had an influence on weight loss in the short and long term, or whether it was a simple matter of the caloric count.