The main structure of the rowing machine and the flat rail belly-rolling machine includes slideway, sliding seat or sliding supports and sliding frame, all of which are equipped with pulley block and pulley bracket, seat plate or supporting handle. The pulley block of the rowing machine is basically the same as the seat plate, and the belly roller is a leg rest. The tilt angles of the two belly tuck machines with the dragging board and the handle are very large, and the tilt angle of the slide rail of the rowing machine is very small, so the belly tuck machine and the front bracket can be adjusted. Add two rotating shaft pedal plates at the left and right of the tail, without special use, just turn the pedal plate of the bicycle, and you can choose between high, middle and low grades, and it will be done. Because it is the resistance of going uphill backwards, just like the original resistance direction, the rowing machine climbs in front and its legs bend and stretch backwards, just to increase the resistance when going uphill, which is consistent with the rowing machine. For the rowing machine, increase the slope as much as possible, and add a U-shaped handle on it, so that the chair can be used as a leg rest. To some extent, it is necessary to increase the resistance. In addition to increasing the slope, elastic ropes and elastic bands can be added under the carriage. When exercising, you can hook the edge of the seat plate with your feet instead of grinding your legs by the friction between your legs and the seat surface. You can add a "backrest" on it, which is reliable, reasonable and ideal, so that your knees can slide up against it, and it can be used as a backrest when rowing, saving touching your ass. Or, cut two concave arcs from the hard board on the inner side of the instep, match with the instep, polish them smoothly, and then cover the instep with EVA pot cover, which does not match with the arch, and can be modified into concave arcs suitable for the instep, one on the left and one on the right. See your cognitive ability and technical conditions for specific details!