Neuroscience 2000 Abstract
| Presentation Number: | 65.8 |
|---|---|
| Abstract Title: | Muscle stiffness can control balance during quiet standing. |
| Authors: |
Winter, D. A.*1
; Patla, A. E.1
; Rietdyk, S.1
1Gait and Posture Lab, University of Waterloo, Waterloo, Canada |
| Primary Theme and Topics |
G. Motor Systems and Sensorimotor Integration - 93. Control of posture and movement |
| Secondary Theme and Topics | G. Motor Systems and Sensorimotor Integration<br />- 96. Sensorimotor integration |
| Session: |
65. Posture and movement: stabilizing Poster |
| Presentation Time: | Sunday, November 5, 2000 11:00 AM-12:00 PM |
| Location: | Hall G-J |
| Keywords: | POSTURE, MOVEMENT, SENSORIMOTOR, STANDING |
Our analysis of a simple stiffness control during quiet standing (winter, et al. 1998) has been challenged by Morasso and Schieppati (1999). They claim that the centre of pressure (COP) will automatically be in phase with the centre of mass (COM) as a necessary consequence of physical laws. However, their arguments and control model ignore the afferent and efferent delays characteristic of all reactive control in many reports in the literature. They also claim that the magnitude of spring stiffness must be well in excess of the gravitational spring, mgh, but their assumption of white noise and spike noise at the muscle level is not valid. Our analysis of the noise at the muscle level revealed that it was a low frequency ripple due to the summation of twitches and it was less than 2% of the muscle tone. Also, their review of stiffness measures in the literature was flawed and our reassessment of their references demonstrates ankle stiffness to be close to the measures reported by Winter, et al. (1998) in spite of the fact most of the studies had their subjects lying prone or supported themselves with their hands while standing. Also, from data on the plantarflexors (Winters and Stark, 1988) the non-linearity of the series elastic element is an essential characteristic which ensures stability in the ankle stiffness control. Finally, in a series of new experiments we analysed the ankle stiffness directly using 3D moments of 10 subjects standing quietly for 10 seconds. A regression of the ankle moment (N.m) vs the ankle (°) yielded the stiffness (N.m/°). The average of these direct measures of stiffness was 808.7 N.m/° which agreed with the values we reported previously (Winter, et al. 1998) and were safely above the gravitational threshold. Winter, et al. J. Neurophysiol. 80:1211-1211, 1998 Morasso & Schieppati, J. Neurophysiol. 83:1622-1626, 1999 Winters & Stark, J. Biomech. 21:1027-1041, 1988.
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2000 Neuroscience Meeting Planner. New Orleans, LA: Society for Neuroscience, 2000. Online.
Copyright © 2000-2025 Society for Neuroscience; all rights reserved. Permission to republish any abstract or part of any abstract in any form must be obtained in writing by SfN office prior to publication.
