7 . Race walking shares many fitness benefits with running, research shows, while most likely contributing to fewer injuries. It does, however, have its own problem.

Race walkers are conditioned athletes. The longest track and field event at the Summer Olympics is the 50-kilometer race walk, which is about five miles longer than the marathon. But the sport’s rules require that a race walker’s knees stay straight through most of the leg swing and one foot remain in contact (接触) with the ground at all times. It’s this strange form that makes race walking such an attractive activity, however, says Jaclyn Norberg, an assistant professor of exercise science at Salem State University in Salem, Mass.

Like running, race walking is physically demanding, she says, According to most calculations, race walkers moving at a pace of six miles per hour would burn about 800 calories(卡路里) per hour, which is approximately twice as many as they would burn walking, although fewer than running, which would probably burn about 1,000 or more calories per hour.

However, race walking does not pound the body as much as running does, Dr. Norberg says. According to her research, runners hit the ground with as much as four times their body weight per step, while race walkers, who do not leave the ground, create only about 1.4 times their body weight with each step.

As a result, she says, some of the injuries associated with running, such as runner’s knee, are uncommon among race walkers. But the sport’s strange form does place considerable stress on the ankles and hips, so people with a history of such injuries might want to be cautious in adopting the sport. In fact, anyone wishing to try race walking should probably first consult a coach or experienced racer to learn proper technique, she says. It takes some practice.

8 . Race walking shares many fitness benefits with running, research shows, while most likely contributing to fewer injuries. It does, however, have its own problem.

Race walkers are conditioned athletes. The longest track and field event at the Summer Olympics is the 50-kilometer race walk, which is about five miles longer than the marathon. But the sport’s rules require that a race walker’s knees stay straight through most of the leg swing and one foot remain in contact (接触) with the ground at all times. It’s this strange form that makes race walking such an attractive activity, however, says Jaclyn Norberg, an assistant professor of exercise science at Salem State University in Salem, Mass.

Like running, race walking is physically demanding, she says, According to most calculations, race walkers moving at a pace of six miles per hour would burn about 800 calories(卡路里) per hour, which is approximately twice as many as they would burn walking, although fewer than running, which would probably burn about 1,000 or more calories per hour.

However, race walking does not pound the body as much as running does, Dr. Norberg says. According to her research, runners hit the ground with as much as four times their body weight per step, while race walkers, who do not leave the ground, create only about 1.4 times their body weight with each step.

As a result, she says, some of the injuries associated with running, such as runner’s knee, are uncommon among race walkers. But the sport’s strange form does place considerable stress on the ankles and hips, so people with a history of such injuries might want to be cautious in adopting the sport. In fact, anyone wishing to try race walking should probably first consult a coach or experienced racer to learn proper technique, she says. It takes some practice.

9 . Physical education, or PE, isn’t required for all high school students. In some schools, it isn’t offered for some different reasons. But should high school students have physical education? The answer is certainly “yes”.

Today many people don’t do sports. But as is known to all, doing sports is essential for an adult. Teaching teens the significance of a healthy lifestyle and making fitness plans now can help teens make exercise their priority as an adult.

High school isn’t that easy. Many students are under a lot of stress. Stress can be harmful to a student’s studies and life. Doing sports can help them deal with stress better, helping them live a happier life at school.

The American Heart Association says that 10 million kids and teens suffer from obesity. Teens should get 60 minutes of physical activity per day to control their weight and to help their bones get stronger. The increase in activities that don’t get teens to move around, such as computer games, means many teens don’t get their required exercise. PE classes act as a public health measureto encourage physical activities and help teens have healthy weights.

Not doing sports increases teens’ hazard of developing many diseases. An active lifestyle offers a good way of protection from these health problems. As much as 75 percent of health-care spending goes toward treating medical conditions that can be prevented by lifestyle changes, according to the American College of Sports Medicine.

According to the President’s Council on Fitness, Sports and Nutrition(PCFSN), students who performed five hours of physical activities each week improved their academic performance. Students from programs with no physical activity, who used the extra time for classroom study, did not perform better on tests than those who gave up some study time in support of physical education.