Abstract: A portable gym using gravitational forces of the present invention includes a gravity gym assembly and a belt harness. The gravity gym assembly includes a door anchor that is attachable to any doorway having a door, and an adjustable strap that leads to a pulley through which a cable passes. The cable is equipped with detachable handles on each end and may be advanced back and forth through the pulley when forces are applied to the handles. A series of exercises may be accomplished by varying body position, and exercises the entire body by using the person's body weight for resistance. In an alternative embodiment, the portable gym using gravitational forces may include attachment of the cable ends to the belt harness worn around the waist of the athlete and provides for the stabilization and application of resistance on the body while exercising.