Abstract: A speed servo-control apparatus is provided for use in combination with a walking-running exercise machine including a moving belt on which a user may walk or run and a direct current drive input for controlling the speed of the moving belt. The apparatus has a frame bracket and a control unit rotatably mounted to the frame bracket, and is provided with an assembly for mounting the frame bracket at a predetermined position with respect to the machine. The apparatus is also provided with a cord assembly having two opposite extremities, one of the extremities being operatively connected to the control unit and the other of the extremities being attachable to the user of the apparatus so as to rotate the control unit in a given direction when the cord assembly is pulled forward.