Vibration-induced postural post-effects.
M. M. Wierzbicka, J. C. Gilhodes, J. P. Roll.
Brockton/West Roxbury VAMC and Department of Neurology, Harvard Medical
School, Boston MA 02132. Laboratory of Human Neurobiology, CNRS 372,
University of Provence, Marseilles, France.
APStracts 4:282N, 1997.
ABSTRACT
It is generally known that vibration of various muscles in free standing
subjects evokes a spatially oriented postural response. Furthermore, it has
recently been shown (Gilhodes et al. 1992) that when a vibratory stimulus is
terminated, a powerful involuntary contraction of the previously vibrated
muscle often occurs which, under the isotonic condition, is accompanied by
movement of a limb. The aim of this study was to explore effects of a low
amplitude mechanical vibration, applied in a seated position, on the standing
posture. The 30-sec vibration was applied bilaterally at the ankle level to
anterior or posterior tendons and at the cervical level in front or back of
the neck, at one site only at a time. Center of pressure (COP) trajectories
were monitored during quiet stance for up to 19 minutes following the offset
of vibration and these measurements were compared with a previbration control
trial. The results clearly indicate that vibration produced in all subjects
strong, long-lasting dynamical modification of posture mainly in the anterior-
posterior direction. Spatial orientation of the induced post-vibratory shift
in posture was dependent on the vibration side. We conclude that sustained Ia
sensory inflow, evoked by vibration, has a powerful after-effect on the motor
system at the postural level.
Received 9 December 1996; accepted in final form 22 September 1997.
APS Manuscript Number J948-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 29 October 1997