Is lying on a rocking machine a healthy exercise?

Sort of. The aerobic swing machine was invented by Japanese medical doctor inspired by goldfish swimming. When the human body is lying flat and completely relaxed, the legs, hips, spine and cervical vertebrae are driven by swinging the feet, so that the muscles and bones of the whole body can carry out full aerobic exercise. Swing machine is a way to swing the spine while lying down, so it is often called aerobic swing machine or swing machine in Chinese mainland.