Treadmills have many advantages over real running and walking. Sure, you don’t get to go outdoors in the nature, but you can also avoid bad weather and all the other hazards that come with going out of your house, such as cars and passers-by. It’s much more relaxing to not have to keep your mind and one eye on the potential problems, and just concentrate on your running.
Apart from that, though, there are many more serious benefits. The ground remains at the same level for the whole run, which avoids you having to constantly adjust the way you’re running – you can build up a pace and then keep going. Also, the run is always at the speed you’re most comfortable with, and you can change it whenever you like. If you do want to run uphill, though, you can simulate that too, by adjusting the gradient of the machine.
Another advantage is in all the statistics you can collect about your running: because the machine is setting the pace of the run, it can calculate all sorts of things automatically, such as the amount of energy (calories) you have burned. You can also hook yourself to various monitors – heart rate monitors, breathing monitors, and so on – to check all the different aspects of your health when you run.
One of the best things about running indoors is that you don’t have to be bored while you’re doing it – you can watch TV or read a book while you’re using it. Even though it can be quite relaxing, though, treadmills are still a more effective form of exercise than some complex cardiovascular exercises. Faced with a choice between getting into all sorts of strange positions and contorting my body into odd shapes or just running on a treadmill, I know which one I’d choose.