A lifting mechanism has a base to which a pivot of a parallelogram structure. A spring extends from a first link of the parallelogram to an adjustable termination point on a second link of the parallelogram to form a lifting triangle. The spring termination point is displaced from a main pivot of the parallelogram to create an adjustable "lever arm" to vary the lifting force. A lifting power adjustment mechanism adjusts the position of the spring termination point. An extension is in fixed relation to one of the parallelogram links and maintains its angle with respect to the horizontal when angles of the parallelogram are varied upon raising or lowering the lifting mechanism between a sitting mode and a standing mode. The extension serves as a base for a rear seat section. A front seat section is pivotally attached to the rear seat section allowing it to swing downward upon elevation of the liftin mechanism.
