Abstract: An exercise device provides first and second foot-support surfaces which are each displaced by an actuator system along an arbitrary path defined in at least two dimensions over a range of at least 25 centimeters by 15 centimeters. A control system is configured to control the actuator system so as to generate an exercise path for each of the first and second foot-support surfaces. The exercise movement may be active or passive, and may be varied dynamically during an uninterrupted exercise session.