A chair assembly includes a base structure, a seat support structure movably coupled to the base structure, an upwardly-extending back support structure movably coupled to the base structure, wherein the back support structure is adapted to move between an upright and reclined positions, wherein the back support structure is operably coupled to the seat support structure, a flexible shell structure defining a forwardly-facing surface forming a lumbar support, wherein the flexible shell is movably coupled to the seat support structure, and a resilient member generating a variable compressive force acting on the flexible shell structure in a manner that tends to cause a curvature of the back support structure to increase, and wherein the compressive force decreases as the back support structure moves from the upright position to the reclined position.