A lot of people have the idea that running on a treadmill is a lesser form of exercise than running outside. It's not. Running on a treadmill is of equal value in terms of aerobic fitness as running on the roads, trails, or tracks. That's your biggest question answered, isn't it? As long as you keep your heart rate in the training range—70 to 85 percent of your estimated maximum heart rate (MHR equals 220 minus your age)—your heart will work just as hard and you'll burn a similar number of calories. A 30-minute run is a 30-minute run, no matter where you do it.
While running outdoors offers changing scenery and terrain and fresh air, running indoors has its advantages. It sure is more pleasant to run indoors when it's cold and icy, hot and humid, or raining outside. It's also safer: You don't have to worry about being hit by a car or getting attacked on a dark street if you're running alone. Treadmills not only wipe out a lot of excuses for skipping runs but also offer options for getting more out of those runs.
Convenience Treadmills are the most popular cardiovascular machines at many clubs. They make it possible for friends who have different speeds to enjoy a side-by-side run. For home use you can purchase machines that are more than adequate for less than $1,000, or you can get luxury models that cost more than $4,000. I had a $700 ProForm treadmill that folded up, which would be a good choice for starters. Now I have a True high-end model with lots of gadgets, which is great. Try the treadmill out before you buy it; as long as it has adequate cushioning and meets your needs in terms of pace and incline, it will work well for you. If you're a slow fitness runner, you won't need a fast-paced machine with a steep incline. But if you're a running pro, you can buy a treadmill with more incline and greater speed. Don't be tempted by cheap nonmotorized machines—most don't have proper cushioning and strain the legs due to the sliding action. Add a basic set of free weights, and you'll save enough money in club dues to make the investment worthwhile quickly—especially if more than one person will be using it.
Consistency Running on a treadmill is different from outdoor running. You can set a consistent pace per mile on a treadmill—which will keep you from running too fast or too slow—though the speeds per mile indicated on computerized machines are often inaccurate. As long as you're exercising at the same perceived exertion level as you do when you're outside and you keep your heart rate in your training range, your exact pace isn't important.
You can add hills at the touch of a button, and—just as important—you can make the hills go away just as fast! Adding hills to your run works different muscles; flat running is powered mostly by the hamstrings, while hills require the quadriceps to do more work. Running on an incline of between 5 and 10 percent should do the trick for fitness runners.
If the treadmill has good shock-absorbing belts, your body will deal with less impact than you would on the road, and you won't ever have to run on a slant, with one leg higher than the other, which will reduce your risk of injury.
In some ways, running on a treadmill is easier than running outside. You don't experience air resistance as your body isn't moving forward, and you don't encounter headwinds. When your foot hits the moving surface there is less braking action than when it hits stationary surfaces, so treadmill running requires less effort. You may feel as though you're running faster on the machine. (If you want an equivalent effort in terms of pace, increase the incline approximately 1 percent.)
To combat boredom, try watching TV, listening to music, or varying the speed and incline slightly. You may get warm in a hurry, so try to exercise near a window or fan, and keep fluids close by for easy hydration.
Fitness runners can ride out bad weather for days at a time by running inside, alternating the treadmill with outdoor exercise year-round, or even by becoming a treadmill-only addict. (Of course, runners who are training for competition will need to do some outdoor work to achieve optimal results.) The important thing is to keep running. Whatever exercise you enjoy the most, whatever you are most likely to do, that's the best choice for you—and your aerobic fitness.