Abstract: A backrest for supporting a person's back having a front surface and a rear surface has a flexible support section having a fixed end which is mounted to a support structure and a free end which is displaceable vertically with respect to the fixed end, the support section is configured to be compressed and displaced forwardly when the free end is moved towards the fixed end; an adjustment member drivingly connected to the free end; and, a detent member for selectively receiving the adjustment member in one of a plurality of positions, the support member biasing the adjustment member into retaining engagement with the detent member due to the compression of the flexible support member by the displacement of the free end towards the fixed end.

Abstract: An office chair incorporates a lumbar support in the lumbar region of the back of the chair. The support includes an arcuate lumbar support element and a carrier for the element, which is pivotally coupled to the back for movement between positions in which the support element provides respectively maximum and minimum support for the lumbar region of the person using the chair. The carrier can be locked in an adjusted position. The support element is resiliently flexible so that its curvature varies between a maximum in the maximum support position and a minimum in a minimum support position of the lumbar support.

Abstract: An office chair has a back with a central portion and respective wings or bolsters on opposite sides of the central portion. The wings are coupled to the main central portion by arm structures that are designed to allow the wings to flex rearwardly from a rest position and back to the rest position in response to forces exerted by a person seated in the chair, but to resist forces tending to move the wings forwardly from the rest position.