the invention concerns a chair (10) with a seat (16) and a backrest (18) and the seat (16), or in a stationary frame on the floor (21) is mounted, and the seat back (18) of the frame (12) and / or with the seat (16) tilt is connected, thereby gekennzeichn et,dasszus u00e4tzlich between the seat back (18) and the frame (12) and the seat (16) by fluidkraft aktivierbare bet u00e4tigungsvorrichtung (24) for the backrest (18) is involved.