A body weight support system that monitors and controls the level of support force within a stepcycle to result in normative center of mass movement and ground reaction forces. The system comprises a harness connected to a lift line which in turn is connected to a means for advancing and retracting the lift line. A control system is configured to monitor load on the cable and to regulate lift line advancement and retraction in response to load information. The support system can be combined with a treadmill for locomotor training of a subject.