If you could peek into every house in your neighborhood on an icy winter afternoon, what do you think you would see?

A lot of kids sitting on sofas watching TV? You're probably right.

People in the United States these days are lucky. We have machines to do a lot of our work, and we travel around in cars. Our great-grandparents would be amazed if they could see how easy things are for us.

Unlike our great-grandparents, we don't have to carry pails of water up and down stairs to fill bathtubs. We don't have to chop wood. We don't have to walk just about everywhere we go.

But there are some bad things about the way we live, too. Our bodies are designed to be used -- and used hard. Sitting around at desks or watching TV all day, our bodies become out of shape. The American Medical Association, a large group of doctors, says that almost one-third of all American children are overweight.

To stay fit, we need to exercise every day. In the summer, it's easy to get lots of exercise riding bikes, swimming and playing games. But winter weather can make exercising a challenge. It's awfully easy to become lazy and just sit around waiting for summer to come again.

Here are some good reasons to keep up daily activity:

Exercise helps you stay fit and resist sickness.

Exercise helps you stay at a healthy weight.

Exercise keeps your muscles strong -- including your heart, a very important muscle. Exercise is fun.

Here are some ways you can exercise on those rainy, cold days when you have to stay cooped up in the house:

Work on improving your balance. Use tape or a long ribbon to make a line on the floor. Pretend the tape is a balance beam or a tightrope. Walk forward and backward along the line.

Develop an iron grip. You can do this exercise while you're sitting around the house. All you need is a small, soft rubber ball. Just squeeze it over and over with each hand. This will make the muscles in your hand and wrist stronger.

Turn your bicycle into an indoor exercise machine. Don't let your bike gather dust all winter. With the help of an adult, use wooden or metal rods to build a sturdy stand. Raise the rear wheel of your bike off the ground by supporting the hub, or center, of the wheel on one of the rods. Make sure your bike is steady, and that the rear wheel isn't touching the ground. Now you can "ride" inside -- even while you watch TV. Bike riding strengthens your heart and keeps your breathing system in good shape.

Meet your muscles.

Lie on your back on a rug, pad or folded blanket. Lie comfortably, with your legs slightly apart. Close your eyes. Now, starting with your left foot, tighten the muscles in your toes. Keep the rest of your body relaxed and loose. Then let the tension in your toes go. Next, tighten the muscles in your foot, hold for a few seconds. Then let go. Do this with each part of your leg: ankle, calf, knee, and thigh. Then do your right leg the same way.

Next, tighten and relax the muscles in your left arm. Start with your fingers. Then squeeze and relax your hand, your forearm, your elbow -- all the way up to your shoulder. Then do the other arm.

Now do the same thing with your stomach muscles. But keep breathing. Then work your neck muscles. Next -- this is a fun part -- tighten up your face muscles as hard as you can. Then relax.

Last of all, make your entire body -- every muscle in you -- tense. Tighten up as hard as you can. Hold it! Then s-l-o-w-l-y begin to let go. Start with your hands, and then let each muscle group relax in turn. If you do these quiet exercises, you'll get to know your body's muscle groups. And you'll relax -- an important part of exercise.

You can probably invent lots more indoor activities that will keep your body in good shape.

Tips for Parents

The "Animal Olympics" exercises that follow were designed by the President's Council on Physical Fitness and Sports. They are recommended for children in the primary grades. Teach them to your children as part of an indoor exercise session:

Tortoise and Hare (cardiorespiratory)

Starting position: Stand at attention.

Action:

Count 1: Jog slowly in place.

Count 2: On the command "Hare," the tempo doubles. The knees are lifted high, while arms pump vigorously.

Count 3: On the command "Tortoise," the tempo slows to an easy jog.

Repeat the commands "Tortoise" and "Hare."

Gorilla Walk (flexibility and coordination)

Starting position: Child spreads feet to shoulder width, bends at the waist and grasps ankles, keeping the knees fully extended.

Action: Walk forward holding firmly to the ankles. Keep the legs straight.

Bear Walk (flexibility, hamstrings)

Starting position: Bend from the waist and place hands on the floor.

Action: Travel around the room in a circle, moving right arm and right leg simultaneously as one step, then left arm and left leg.

Exercises adapted from "Youth Physical Fitness," President's Council on Physical Fitness and Sports, U.S. Government Printing Office, 1983.