A vehicle seat comprising a seat back including a backrest support and a backrest, the backrest including a deformable back-support panel configured to bend and flex to move relative to the backrest support to assume many different shapes to provide custom spinal column support to a passenger seated in the vehicle seat adjacent to the deformable back-support panel, a back-support panel-motion controller coupled to the deformable back-support panel and configured to provide means operable by the passenger seated in the vehicle seat for moving the deformable back-support panel relative to the backrest support in an initial stage of active operation to assume a selected shape in response to activation of an actuator included in the back-support panel-motion controller and for independently allowing the selected shape of the deformable back-support panel to vary passively after assumption of the selected shape in a subsequent stage of passive operation without activating the actuator in response to forces applied by a torso of the seated passenger leaning against the deformable back-support panel as the seated passenger shifts position relative to the seat back to assume a new posture in the vehicle seat, and a seat bottom adapted to lie under and support the seated passenger and wherein the seat back is arranged to extend upwardly from the seat bottom, the deformable back-support panel includes an upper portion arranged to lie in spaced-apart relation to the seat bottom and a lower portion arranged to lie between the seat bottom and the upper portion, and the back-support panel-motion controller includes a lower control unit coupled to the lower portion of the deformable back-support panel and configured to provide active-motion means for actively moving the deformable back-support panel relative to the backrest support to cause the shape of the deformable back-support panel to change to assume the selected shape so that lumbar support for the seated passenger leaning against the seat back is varied to suit the passenger and to provide lower passive-motion means for passively allowing shape-changing movement of the deformable back-support panel temporarily away from the selected shape and relative to the backrest support in response to rearwardly directed forces applied by the seated passenger during a shift in position of the seated passenger on the seat bottom and relative to the seat back to assume a new posture in the vehicle seat, wherein the lower control unit includes a lower panel mount (71, 72) coupled to the lower portion of the deformable back-support panel, a link mover separated from the deformable back-support panel, and a shape-control link (74, 174) arranged to interconnect the lower panel mount (71, 72) and the link mover, wherein the link mover is configured to provide means for actively moving the shape-control link (74, 174) relative to the backrest support to cause movement of the lower portion of the deformable back-support panel relative to the backrest support so that the shape of the deformable back-support panel is varied to assume the selected shape to suit the seated passenger, and characterized in that the shape-control link (74, 174) comprises an input block coupled to the link mover, an output block (78, 178) coupled to the lower panel mount (71, 72) using an axle rod, and a yieldable spring (77, 177) made of an elastic material and arranged to interconnect the input block and output block (78, 178).