An improved treadmill comprises a motor driven endless belt, sensors located below an upper run of the belt for sensing the position of a user, and a controller for controlling the speed of the belt in accordance with the position of the user relative to the sensors. The detection or lack of detection...http://www.google.co.uk/patents/US5368532?utm_source=gb-gplus-sharePatent US5368532 - Treadmill having an automatic speed control system
