Interaction between postural asymmetry and visual feedback effects in undisturbed upright stance control in healthy adults.
OBJECTIVE
The technique of additional visual feedback has been shown to significantly decrease the center of pressure (CP) displacements of a standing subject. Body-weight asymmetry is known to increase postural instability due to difficulties in coordinating the reaction forces exerted under each foot and is often a cardinal feature of various neurological and traumatic diseases. To examine the possible interactions between additional visual feedback and body-weight asymmetry effects, healthy adults were recruited in a protocol with and without additional visual feedback, with different levels of body-weight asymmetry.


METHODS
CP displacements under each foot were recorded and used to compute the resultant CP displacements (CPRes) and to estimate vertically projected center of gravity (CGv) and CPRes-CGvdisplacements. Overall, six conditions were randomly proposed combining two factors: asymmetry with three BW percentage distributions (50/50, 35/65 and 20/80; left/right leg) and feedback (with or without additional VFB).


RESULTS
The additional visual feedback technique principally reduces CGvdisplacements, whereas asymmetry increases CPRes-CGvdisplacements along the mediolateral axis. Some effects on plantar CP displacements were also observed, but only under the unloaded foot. Interestingly, no interaction between additional visual feedback and body-weight asymmetry was reported.


CONCLUSIONS
These results suggest that the various postural effects that ensue from manipulating additional visual feedback parameters, shown previously in healthy subjects in various studies, could also apply independently of the level of asymmetry.


CONCLUSIONS
Visual feedback effects could be observed in patients presenting weight-bearing asymmetries.
Laboratoire interdisciplinaire de biologie de la motricité, université de Savoie- Mont Blanc, domaine scientifique de Savoie-Technolac, 73376 le Bourget du Lac cedex, France. Electronic address: patrice.rougier@univ-savoie.fr.
Patrice R
PR
Rougier
Laboratoire interdisciplinaire de biologie de la motricité, université de Savoie- Mont Blanc, domaine scientifique de Savoie-Technolac, 73376 le Bourget du Lac cedex, France.
Samir
S
Boudrahem
D000328:Adult; D001835:Body Weight; D056228:Feedback, Sensory; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D004856:Postural Balance; D011187:Posture; D016474:Weight-Bearing
Augmented visual feedback; Body-weight distribution; Posturographie; Posturography; Répartition du poids de corps; Rétroaction visuelle augmentée; Station debout; Upright stance