The Triangular Oscillating System (T.O.S.) provides a gentle rocking motion rather than just up and down movement as a way of reducing the impact on joints and ligaments. There is a substantial difference between T.O.S. and "vertical", "Linear" or ¡°tri-planar¡± vibration used by many other vibration machines (like the PowerPlate) that can cause stress to those areas. All the best research in whole body vibration done by Vladimir Nazarov (original pioneer with Russian Space Program), Carmelo Bosco and Marco Cardinale was done using THIS type of motion (also called oscillating, pivotal or teeter-totter). Pivotal is more like the way we move or walk. Think about it, kangaroos hop up and down and a linear / vertical MIGHT work for them¡¦ But as we "humans" walk, we shift our weight from side to side with one foot on the ground at a time. Also this motion creates a nice sine wave like motion up and down the spine contrasted to a "jack-hammer" like jarring motion of lineal or triplanar machines.