Abstract: A back construction includes a back shell having stiff thoracic and pelvic regions connected by a flexible lumbar region in a manner adapted to ergonomically support a seated user. The back shell includes spaced-apart resilient edge strips and leaf springs attached to or embedded into the edge strip. The springs match a curvature of the strips and span the lumbar region, biasing the lumbar region of the back shell forwardly in a manner distributing stress applied to the lumbar region by the seated user.

Abstract: A seating unit includes a seating unit having a base, a seat and a back operably pivoted to the base for synchronous movement including recline of the back and forward movement of the seat, an adjustable variable back stop adjustably engaging the seat for adjustably limiting a rearward tilt of the back, and a handle. The handle and the back stop are supported for independent movement, but are interconnected by a connecting mechanism including a pair of links so that the back stop is selectively adjusted upon rotation of the handle.

Abstract: A back construction includes an inverted U-shaped back frame and a back shell supported on the back frame and having stiff thoracic and pelvic regions connected by a flexible lumbar region in a manner adapted to ergonomically support a seated user. The lumber section includes a plurality of vertically spaced slots to increase its flexibility. The back shell has a complex curved shape that is forwardly concave in horizontal cross section and forwardly convex in vertical cross section. A force-generating mechanism biases the lumber section forwardly for lumbar support to a seated user.

Abstract: A back construction includes a back shell having stiff thoracic and pelvic regions connected by a flexible lumbar region in a manner adapted to ergonomically support a seated user. The back shell includes springs that press on a rear surface of the back shell to bias the flexible lumbar region forwardly so as to support a seated user, thus biasing the lumbar region of the back shell forwardly in a manner distributing stress applied to the lumbar region by the seated user.