Abstract: A chair adapted to passively adjust itself to be in equilibrium with the user's body in relation to changes in the center of gravity and thigh inclination. The chair includes a post from which is provided, in one embodiment, a convex track on which a carriage is allowed to travel, and a seat pan is pivoted on the carriage for angle adjustment relative to the carriage. In another embodiment, a first concave track is provided on the top of the post with a carriage slidable in the concave track and a seat pan mounted for travel in a track on the carriage wherein the second concave track has a smaller radius than the first track.

Abstract: A tilting seat having a base for supporting the seat on the floor and a stem extending upwardly from the base, either integrally or separably from the base, the seat being arranged such that it tilts about a tilting axis passing through the base such that a user can tilt the seat forward when in a working position. The base may be a turntable.