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/goals. If you are more concerned with detoxification and lymphatic drainage, you may wan a pivotal, spiral or sonic machine.