Abstract: An operating bar can be moved between limit positions at least 180.degree. apart, and a sprocket on the axis of motion carries a chain connected to a lever for exerting a near constant reaction force or torque. A bellcrank on the same axis carries weights that provide a variable force or torque on the movable bar. The user can assume one position to move the bar in a biceps exercise mode and another position to move the bar in a triceps exercise mode. The bellcrank has two pins to support weights in two angularly related positions to provide a desired force variation for each such exercise mode.