Apparatus for passively exercising the human extremities includes an elongate track (16) comprising a tubular housing (46) having a slot formed in the bottom thereof. A lead screw (62) is longitudinally disposed in the housing and a carriage (26) is threadably engaged with the lead screw (62). The carriage (26) is connected to the extremity to be exercised, so that upon movement of the carriage (26) back and forth along the elongated track (16) the extremity is moved through a pre-determined range of motion. Stop members (28) are positionable on the housing in the path of movement of the carriage (26). Engagement of the carriage (26) with the stop member (28) effects longitudinal shifting of the lead screw (62). Longitudinal shifting of the lead screw (62) actuates switches (110) which reverse the direction of rotation of the lead screw (62) thereby reversing the direction of movement of the carriage (26).
