A comparison of three vibrators in static posturography: the effect of vibration amplitude on body sway.

In static posturography, proprioception is often disturbed using vibrators applied bilaterally to the calf muscles. The effect of vibrator amplitude on body sway was compared in static posturography using bilateral vibrators on the calf muscles of 30 healthy male military conscripts at frequencies of 50 and 90 Hz. Postural stability was measured in terms of BSV (body sway velocity), and maximal displacements of the centre of force (MAXY, MAXX) in the anterio-posterior and lateral directions. In comparing the effects of vibration to base stance without vibration, BSV seemed to be the most sensitive parameter. A vibration of 50 and 90 Hz significantly influenced BSV values with the two most eccentric loads, an effect which could not be confirmed using any other parameter. This result could be obtained even with a small amplitude (around 0.7 mm free/0.3 mm fixed) in our healthy subjects. The BSV effects may be even more pronounced in clinical work with patients and postural disorders. Thus, when proprioceptive stimulations is used in posturographic measurements, differences in the tested magnitude of the stimulation amplitude with a constant frequency will significantly affect postural stability, even in healthy subjects.