When we run on an incline, in addition to running forward, we are moving upward against the force of gravity. Our legs are performing work by lifting our body mass up – like walking up stairs. The work is defined as force against gravity times the distance. On a treadmill you are basically running at a fixed height. To simulate the extra load you would be facing on an incline, the internal mechanism gradually puts more load on the rollers.. If that were to happen quickly you would suddenly run forward. To further add realism the platform tilts a certain amount to make you think you are on a real world incline. It also helps make your feet and ankles bend as if you were. But…. Making a moving incline with the required actuators is expensive and theoretically unnecessary since it is easy to simulate the load, So, as an engineering/marketing compromise, they give you a little lift and add load to the drive system. Don’t worry. Even though you are not actually going up an incline your body is still doing the same workout. Incline or no, the device will still work as a perfect clothes rack 4 months after you get it.