A vehicle seat includes a backrest coupled to an upwardly extending support frame. The backrest includes a deformable seat shell adapted to assume various shapes between an initial position and a final position in response to variable rearward loads applied by the torso of a seated passenger. The seat shell is coupled to the support frame by a compliant shell-motion controller via upper and lower motion-control links. At least one of the motion-control links includes a flexural portion configured to bend about a pivot axis to establish a flexural joint. The lower motion-control link may include a flexural joint and/or a revolute joint, and the upper motion control link may include a flexural, revolute, or spheroidal joint.