You may opt to run on a treadmill because it is convenient but you may be choosing the treadmill because it is easier as well. Have you ever run three miles on a treadmill and thought, "That was a piece of cake," but then when you run three miles outside you think, "I thought I was in shape; that was so hard!"
The reason is that running on a treadmill is a lot different than running outdoors and here are several reasons why:
- The rearward rolling treadmill belt offers help to your legs by pulling your feet back underneath your body, which means you could be exerting less energy to move your feet and legs than if you were running outdoors on a surface that doesn't give your legs momentum.
- When you run on a treadmill, you do not have to overcome any kind of wind resistance, which means you'll use less energy than if you were running with wind resistance. More than just wind though, running indoors maintains or offers stable elements. Indoor runners avoid cold/hot air, rain or sand, gravel, dirt, natural increase/decrease in the gradients of the pavement and other outdoor obstacles. Your body’s natural efforts to acclimate itself to these varying elements requires much more energy than the flat, cushy treadmill surface.
- Pace is steady on a treadmill because it runs on a set (or variable) speed and your body has ample time to adjust. When you run outdoors, it is a different story because you no longer have a machine keeping pace, so if you are not skilled at pacing yourself, you either under or overcompensate which could make you winded.
Fit's Tip: If you are training for a race, you definitely want to train outdoors to properly get your body (physically and mentally prepared).