Benefits of postural sway to succeed in goal-directed visual tasks
Résumé
When individuals stand, they sway and so have to maintain their balance. It is generally
expected that task performance is worse when standing and swaying than when sitting and
therefore not swaying. In contrast, we hypothesized that greater sway is associated with better
task performance in the absence of external perturbations of posture. Twenty-four healthy,
young adults performed two goal-directed, modified Stroop tasks (incongruent and reversed
incongruent) in four body position conditions (standing against a vertical surface, and standing
freely with a wide, standard or narrow stance). Centre of pressure (COP) sway, head sway, eye
movements, visual attention, and task performance were recorded. Partial correlation analyses
showed significant positive associations between task performance and some COP and head
sway variables, after controlling for the level of visual attention. Analyses of variance with
three factors (body position, task difficulty, target distance) also showed significant interaction
effects between body position (and therefore postural sway) and the number of accurate target
findings. The presence of these interactions showed that narrow stance was both the best body
position for performing the incongruent task and the worst body position for performing the
reversed incongruent task. Overall, COP sway and head sway can increase task performance.
Hence, healthy, young adults in quiet stance appear to use sway to explore their environment
more effectively. However, it should be borne in mind that our hypothesis was formulated
solely with regard to healthy, young adults standing in quiet stance .