Abstract: The structure (1) supporting the body on the seat is subdivided into a front seating part (2) articulated on the frame (5), a back (4) articulated on a bracket (10) which is itself articulated on the frame, and a rear seating part (3) articulated between the back (4) and the front seating part (3). A non-rigid connection (14) is provided between the rear seating part (3) and the bracket (10).