The wheelchair (1) has a frame (2), and a seat (3) comprising a seat part (8) for sitting a person. Drive wheels (4, 5) are provided for rolling the wheelchair, and a drive device (15) drives one of the wheels, where the seat and the wheels are fastened to the frame. The drive device is mechanically coupled with the seat part and/or a backrest portion (9) such that the seat part and/or the backrest portion are moved relative to the frame by the drive device for moving buttocks of the person sitting on the seat. The drive device has a muscle-operated lever arm element. Independent claims are also included for the following: (1) a retrofit kit for a wheelchair (2) a method for operating a wheelchair.
