Despite the larger amplitudes of side-alternating systems, the vibration (acceleration) transmitted to the head is significantly smaller than in non-side-alternating systems ("Abercromby et al. 2007") while at the same time muscle activation even at identical vibration parameters are increased in pivotal systems. However, standing with both heels on one side of a side-alternating machine facing side-ways results in significant acceleration transmitted to the head and center of gravity of the upper body. At least one such WBV owner's manual suggest this variation calling it "Stand-a-side Pose". At the outer edge of the plate the amplitude is typically about 10 mm, which is more than the 3 mm maximum of a linear vibrator and not practical. The amplitude and impact  can be reduced by centering, e.g., a gardener's knee pad, ~ 16"x 8" x 3/4", on the plate and standing with the heels toward the outer edge of the pad. While this is useful it does not replace a machine whose entire plate moves up and down in a linear fashion allowing for a variety of positions and activities.