Yes, most of the national fitness machines in outdoor open-air squares are based on a simple principle, that is, using levers and axles to transmit exercise strength from people. There are several kinds of outdoor treadmills. One is that there is a row of axles at the position of the running board, on which athletes will roll, and running means continuing to tread. The second kind of treadmill is to stand on the pedal with two feet, hold the push handle back and forth, and push the handle forward while pedaling, thus forming the knowledge of running.