A chair includes a base having a control assembly operably supporting a seat
assembly
and also a back assembly for movement about a seat tilt axis and a back tilt axis,
respectively. The back assembly includes a flexible sheet supported at upper/outer
corners by a back support structure and hanging downwardly. The flexible sheet
includes a lower portion coupled to the back support structure by a tensioner for
holding the lower portion rearwardly. A vertically-adjustable lumbar mechanism
is adjustably supported on the back support structure and operably engages the
flexible sheet for flexing a lumbar area of the flexible sheet forwardly to provide
an optimal ergonomic horizontal and vertical convex shape for postural lumbar support.
