Also, there is no way that I would trade running outdoors for running on a treadmill. I absolutely need the fresh air, sunlight (even if it's coming through clouds), and sense that I'm actually progressing rather than running in place. I would not run on a track (even if there was one near my house), either, since I need my surroundings to change as I jog, and I need inclines in order to get better strength training and to get my heart pumping more.