Ever wonder why treadmills always seem to be the perennial favorites at the gym? They provide good aerobic exercise, for one. They're not only popular pieces of equipment at the gym; many people buy them for home use. Beginners flock to treadmills because they can start using them by doing something they do daily anyway: walk. What makes treadmills so beloved in the fitness world is that a person of any fitness level can use one.1. Easy to Use The treadmill is easy to use, and its surface is easier to negotiate than outdoor walking surfaces, such as walking trails, sidewalks and streets. Your risk of tripping over something is reduced on a treadmill. And you don't need to deal with wind resistance, which makes your workout more difficult, as you would outdoors. The padded surface lessens impact, which is a relief if you're overweight or have knee problems. If you want to be challenged as much as you would be outside, simply set the incline to 1 percent. That way, you get the benefit of expending more energy without the hassles you sometimes deal with outside. 2. Easy to Control You can control every aspect of your workout with a treadmill: speed, incline, length of warm-up and cool down periods and length of time for the workout itself. You're also in a weather-controlled environment. Having a treadmill available indoors can make the difference between working out or not when the weather's bad. 3. You Can Multitask If you were going to read the newspaper, a magazine article or watch a TV show anyway, you can kill two birds with one stone by using a treadmill. You can easily get into a routine, for example, by watching a favorite half-hour TV show while using a treadmill. This keeps you from becoming bored on the machine. 4. Improves Your Health Regular use of a treadmill, 20 minutes of moderate exercise on it every other day, can improve your overall cardiovascular health. Plus, treadmills burn the most calories compared with all the other cardio machines you see at the gym: the elliptical, stationary bikes, stair steppers and rowing machines. If you walk briskly on a treadmill, you can burn 100 calories per mile. 5. Provides a Diverse Workout Walking, jogging and running are what people typically do on treadmills. But you can use them for more than that. You can get a good interval-training workout; you can skip, and you can set a treadmill to simulate hill climbing. You can even dance on one, but that's reserved for advanced treadmill users only. Make a simple brisk walking routine more interesting by using a preprogrammed workout that varies the routine for you, or vary it yourself by changing the incline and the speed as you like.