UBC Theses and Dissertations
The role of visual sampling in obstacle compensation Vienneau, Opal Yvette
Most obstacle avoidance studies have identified the importance of visual information in choosing obstacle avoidance strategies and of kinesthetic information for successful clearance of obstacles. The intent of this investigation was to determine on what and how visual information is utilized when an obstacle is encountered in our travel path and on some of the subsequent gait adaptations made to accommodate it. Accommodation strategies are based on movement goals and, in the case of this experiment, the goal was to step up onto a platform of set height and width but placed at varying distances from the subject's start position. Twelve volunteers completed seven walking trials for each of four obstacle placement conditions. The kinematic properties of their gait and the corresponding eye movements were recorded and analyzed to determine whether there was an inherent pattern in accommodating obstacles. Subjects were found to slow down in mid path and make changes to their stride length. Smaller adjustments were applied within the last two strides before the obstacle. Stride length change was the primary method of adaptation. Subjects focussed primarily on the obstacle throughout the trials, however gaze time on the obstacle decreased as the subjects approached the point of step-up. The normal condition, set at a natural right-foot step-up position, presented the least change in stride and exhibited patterns similar to those observed in the control situation where there was no obstacle. The greatest effect of stride was observed for the close obstacle placement, while for the far obstacle placement participants displayed similar patterns that were less pronounced. The results of the present experiment indicated that multiple visual sampling was necessary in all strides to apply adaptations to gait.
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