Abstract: An apparatus—which could be a chair (10), but could also be an apparatus that supports a person in other than a seated position—comprising a moveable platform (including a seat (12) in case of a chair) urged always toward a neutral position when a person is seated or otherwise positioned on the apparatus (10). The motion of the platform/seat (12) toward and away from the neutral position is constrained so that the platform/seat (12) remains at least approximately horizontal in its orientation relative to the floor on which the apparatus/chair (10) is positioned even when traveling along a path not horizontal to the floor, i.e. e.g. along a path inclined to the floor. A method is also provided in which the apparatus/chair (10) is used to provide lower-back therapy.