be understood that the handles 30 and 32 are interchangeable with each other in all respects except that the handle 32 allows free rotation with respect to the attached gas resistance unit 17 while the handle 30 is fixed with respect to rotation of the attached gas resistance unit 17 the modular exercise device 15 is reciprocal toward a compressed position as shown by the dotted lines in fig5 by compressive force on the handle 30 on the first end 16 of the cylinder 19 and the handle 32 on the second distal end 24 of the piston rod 20 relative to each other thereby compressing the pressurized gas in the cylinder 19 from a compressed position the modular exercise device 15 is reciprocal to an expanded position by release of the compressive force thereby allowing the pressurized gas to expand against the piston urging the piston rod 20 outward the gas unit 17 provides resistance to the efforts of an individual on the ends of a modular exercise device according to the present invention on a compressive stroke since the compressed gas unit 17 responds slowly to a release of compressive pressure the individual can increase his or her exercise by exerting traction to draw the expanding gas unit 17 outward due to the screw engagement of the handles 30 and 32 the modular exercise device 15 can be easily.