Article

The purpose of the present study is to demonstrate whether the time taken to
initiate a lift-one-leg task from a quiet standing position is determined by the
initial weight distribution (WD), irrespective of whether the initial posture is
controlled spontaneously or by using visual feedback. Seven healthy young
subjects performed a lift-one-leg task in response to visual stimulation provided
by an LED. The experiment included the normal (N) condition in which the
participants stand on both legs symmetrically, as subjectively estimated, and the
three feedback (FL, FC and FR) conditions in which the participants regulate the
WD at -20% (left-weighted by 6:4), 0% (center-weighted by 5:5) and 20%
(right-weighted by 4:6), respectively, through the use of visual feedback. In the
N condition, the inter-trial variation of WD was larger than that of the FC
condition, which was enough to significantly correlate with the time required to
lift the leg. The slope, intercept, and standard error of estimation of the
regression equation between the WD and the duration of anticipatory postural
adjustment were consistent between conditions. The quantification of the effect
of WD on anticipatory postural adjustment indicated that the time taken to lift
the leg was delayed by 2.81ms as the center of mass shifted toward the lifting
leg by 1mm. Our results demonstrate that asymmetric loading is a simple
biomechanical factor that determines the time needed to initiate a subsequent
lift-one-leg task.

Langue : ANGLAIS