The parallel bars lift the knees: the movement is simple, the upper body does not move, the legs naturally droop, the knees are lifted to the extreme, the contraction reaches the peak, and they return at a constant speed. In order to pursue high difficulty, they can't bend their knees and turn into parallel bars to lift their legs. Be careful not to swing your body at a uniform speed, and pay attention to the speed. It's easy to get hurt on the swing.