The seat back for the seat of a vehicle has a lordosis plate connected at the upper end to a transverse rail and in an intermediate area to an adjusting lever which in its turn is connected to a Bowden cable. A support frame (1) fitted in the seat back and includes the transverse rail (4) and a foot rail (6) which in the plane of the support frame is flexible and twistable around its axis. The adjusting lever (13) is constructed in one piece to the foot rail or foot end of the support frame, and the Bowden cable acts upon the foot rail.
