Abstract: A frame structure mounts two side-by-side steps which are pivotally connected to the frame structure for up-and-down motion. The up-and-down motion of each step is translated to rotary motion by a first and second pulley. The first pulley is connected to the first step by a strap which has one end connected to the strap and the other end connected to the first pulley. The second pulley is connected to the second step by a second strap which has one end connected to the second step and the other end anchored to the second pulley.