The seat (1) has a padded seat area (2) and an ergonomically shaped backrest (3). The frame (4) of the backrest (3) is assembled of a flexible central panel (5) and two S-shaped bars attached laterally to the panel (5) with small bows. Swivel bearings are located in the shoulder (19) and the pelvis area (20). When the occupant of the seat pushes the shoulder area (19) to the back, the pelvis supporting area (20) is moved to the front and vice versa.