Measurement of visco-elastic properties of muscles around the ankle during standing.

The aim of this study was to determine elastic and viscous coefficients of muscles around the ankle during standing, and to investigate whether these coefficients depended on the balance task. By means of a servo-controlled platform, angle disturbances of the ankle were imposed upon a standing subject under three conditions: (a) standing on both legs with eyes open, (b) standing on both legs with eyes closed and (c) standing on one leg with eyes open. Visco-elastic properties of muscles around the right ankle of seven subjects were estimated using data for ankle moment and angle. Mean elastic coefficients changed from 151 to 220 Nm/rad and mean viscous coefficients changed from 15 to 49 Nms/rad. Both of them tended to increase as the balance task became more demanding, i.e. in the order (a), (b) and (c).