Exercise is the best way to stay healthy. But few people get enough exercise. Only 20% of Americans get 150 minutes of physical activity every week. More than 80 million Americans over 6 years old are not active (活跃的).
Many US schools cut (削减) PE classes. Only 15% of schools have this class at least three days a week.
This year, the US National Institutes of Health (NIH) starts an important study. It will show the things happening inside a body after exercise. The NIH hopes to tell people that exercise is a kind of good medicine.
The study will run for six years. It studies a group of about 3,000 people. They are from the 11-year-olds
to the old. The study has shown many nice changes in the body during and after exercise so far.
And the study has also shown that housework can be physical exercise. "Cutting the grass, cleaning rooms, washing the car — all of these are exercise," says a scientist. "Exercise isn't just throwing a ball into a basket."
