Volume 50: 405-410, 2001

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Human Postural Responses to Different Frequency Vibrations of Lower Leg Muscles


A. POLÓNYOVÁ, F. HLAVAČKA

Institute of Normal and Pathological Physiology, Slovak Academy of Sciences, Bratislava, Slovak Republic


Received June 8, 2000
Accepted November 30, 2000


Summary
We analyzed human postural responses to muscle vibration applied at four different frequencies to lower leg muscles, the lateral gastrocnemius (GA) or tibialis anterior (TA) muscles. The muscle vibrations induced changes in postural orientation characterized by the center of pressure (CoP) on the force platform surface on which the subjects were standing. Unilateral vibratory stimulation of TA induced body leaning forward and in the direction of the stimulated leg. Unilateral vibration of GA muscles induced body tilting backwards and in the opposite direction of the stimulated leg. The time course of postural responses was similar and started within 1 s after the onset of vibration by a gradual body tilt. When a new slope of the body position was reached, oscillations of body alignment occurred. When the vibrations were discontinued, this was followed by rapid recovery of the initial body position. The relationship between the magnitude of the postural response and frequency of vibration differed between TA and GA. While the magnitude of postural responses to TA vibration increased approximately linearly in the 60-100 Hz range of vibration frequency, the magnitude of response to GA vibration increased linearly only at lower frequencies of 40-60 Hz. The direction of body tilt induced by muscle vibration did not depend on the vibration frequency.


Key words
Postural responses · Vibration frequency · Lower leg muscles · Man

 

Reprint requests
F. Hlavačka, Institute of Normal and Pathological Physiology, Slovak Academy of Sciences, Sienkiewiczova 1, 813 71 Bratislava, Slovak Republic. E-mail: hlavacka@unpf.savba.sk


PHYSIOLOGICAL RESEARCH
© 2001 by the Institute of Physiology, Czech Academy of Sciences

ISSN 0862 - 8408

Issue 4