Being physically active is one of the most important steps people of all ages can take to improve their health.

Yet despite everything we know about the benefits of exercise, only half of U.S. adults and only about a quarter of high school students get the amount recommended in national guidelines.

If you haven't gotten onboard with the program, it's easy to start -- and walking is a perfect path to fitness. That's because it doesn't require any special skills or expensive equipment -- just a good pair of shoes.

Walking not only gets you aerobically fit, it can help with problems such as insomnia, diabetes and even a depressed mood. Walking also has a lower risk of injury than high-impact activities like running. And you can walk year-round, indoors or out.

Start at your own speed and walk in short increments, say for five minutes three times a day. Then gradually increase both length and intensity over time as you develop stamina.

Depending on where you live, however, you may not be able to just walk out of your front door and go. More than 30 percent of people 16 or older live in neighborhoods without sidewalks. The U.S. Surgeon General has called on communities to make walking more accessible to residents. Until then, ironically, you may have to drive to take a walk at a park or on a school track, for instance.

Keep in mind that you can walk at your convenience if you have a home treadmill. These machines aren't just for running, plus they can also keep track of miles logged and calories burned, and many can be set to increase the difficulty of your workouts.