Spring Running: Transitioning From the Treadmill to the Road With Spring just around the corner, now is the time to turn off that treadmill and hit the open road. Running indoors is pretty different than pounding the sidewalk because when you run outside, you lose the assistance of the treadmill pulling your legs backward, which means your body has to work harder and strike surfaces with more energy. Here are some tips to make the transition smoother for you.