An apparatus is disclosed for monitoring the movement and force production of the lumbar spine during flexion and extension in each of several sagittal-frontal planes of the body, as well as during movement in the transverse (twisting) plane. The apparatus includes a rotatable platform upon which the patient is adapted to stand, and the platform is pivotable about a vertical axis, so that the platform may be pivoted to a selected angle and held in the selected position. For operation in the flexion/extension mode, there is provided a lever arm which is rotatable about a horizontal axis which is adapted to pass through the lumbro-sacral junction of the patient, and a first upper body engaging member is releasably mounted to the lever arm. A first computer controlled drive motor pivotally rotates the lever arm in opposite directions in accordance with a predetermined program. An overhead frame assembly is also mounted for rotation about the horizontal axis, and a second upper body engaging member is mounted to the overhead frame assembly for rotation about a generally vertical axis which is perpendicular to the horizontal axis. Thus the apparatus may be operated in a flexion/extension mode, or in a twisting mode, and with the foot platform in a selected angular position.