题目内容：

Why Exercise Is Cool?

1. Exercise Strengthens Muscles

Did you ever do a push-up or swing across the monkey bars at the playground?    1.      By using your muscles to do powerful things, you can make them stronger. For older teens and adults, this kind of workout can make muscles bigger, too.

2.   2.  

Can you touch your toes easily without yelling ouch? Most kids are pretty flexible, which means that they can bend and stretch their bodies without much trouble. Being flexible is having “full range of motion,” which means you can move your arms and legs freely without feeling tightness or pain.

3. Exercise Keeps the Balance

3.   Your body needs a certain amount of calories every day just to function, breathe, walk around, and do all the basic stuff.   4.    If you’re not very active, your body won’t need as many calories.

Whatever your calorie need is, if you eat enough to meet that need, your body weight will stay about the same. If you eat more calories than your body needs, it may be stored as extra fat.

4. Exercise Makes You Feel Good

It feels good to have a strong, flexible body that can do all the activities you enjoy—like running, jumping, and playing with your friends. It’s also fun to be good at something, like scoring a basket, hitting a home run, or perfecting a dive.

But you may not know that exercising can actually put you in a better mood.5.    It’s just another reason why exercise is cool!

A. So you want to do some aerobic (有氧的) exercise right now?

B. Food gives your body fuel in the form of calories, which are a kind of energy.

C. When you exercise, your brain releases a chemical, which may make you feel happier.

D. Those are exercises that can build strength.

E. Exercise Makes You Flexible

F. Exercise Makes Your Heart Happy

G. But if you’re active, your body needs an extra measure of calories or energy.