Linear machines (move straight up and down like a jack hammer) are great for building muscle, but is a very rough motion for your body. Today many linear motion machines have been upgraded to a tri-planar motion. Tri-planar move up and down like a linear machine, but also forward and backwards, so you get the muscle building effects of a linear machine, but without the wear and tear on your joints. Tri-Planar machines are great for weight loss, muscle toning, bone density, but you will also see some benefits in circulation and detoxification. But again, consider your needs and goals. If you are more concerned with detoxification and lymphatic drainage, you may want a pivotal, spiral or sonic machine.