The chair (2) has a base (10) supported by a frame (16). The frame is equipped with six wheels (812, 822, 121, 122, 181). A clamp is subjected to an action of a dedicated unit (101, 102) for damping pivoting movements of the clamp around a transversal axis. Anti-tilting rollers are supported with each other by an arm (201) articulated on rear of the frame around another transversal axis (Y20). The arm is subjected to action of another dedicated unit (211) of damping the pivoting movements of the arm around the latter transversal axis.
