Each of a plurality of weights has a central hole and a slot extending through the central hole. A shaft has a grip handle. A rotatable spindle extends through the grip handle with a plurality of cam plates adjacent to each end of the spindle and an adjustment knob at each end of the spindle. The cam plates each have an outer diameter adapted to fit the central hole of a weight. The weights include a set of weights positioned adjacent to each end of the rotatable spindle and adjacent to the cam plates. A holder is cooperable with the shaft with protrusion blocks adapted to cooperate with the shaft to form a self-locking mechanism.