You'll feel your core and balance kicking in and lots of muscles in your calves, quadriceps and hips being activated. Try this for at least 5 minutes. When you feel adjusted increase the speed by .5 per mile increments. Many individuals, depending on their fitness or coordination level, will quickly be up to 4 mph without holding on to the rails. Make it more dynamic by lowering your center of gravity into a one-quarter squat position, keep your back straight and don't lean forward. Walking backwards on a treadmill can burn up to 20 percent more calories than forward because your pushing your body to do something that it isn't used to and forcing it out of it's comfort zone...and that's the way to get past your plateau!