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Melissa Parade, Brett Fajen; How do the biomechanics of walking constrain the visual control of stepping over obstacles?. Journal of Vision 2015;15(12):1323. doi: 10.1167/15.12.1323.
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© 2017 Association for Research in Vision and Ophthalmology.
The normal human gait cycle is to a significant degree driven by the passive physical forces acting on the structure of the body, but must be adjusted on the basis of visual information when walking over complex terrain. Visual information about the layout of flat terrain features is picked up two steps ahead in order to enact adjustments that secure foot placement on the basis of passive physical forces, which suggests that the use of visual information is constrained by the biomechanics of walking. When the terrain also contains raised obstacles, foot placement must be controlled with respect to an obstacle’s location ahead of time, but foot elevation, which depends on obstacle size, requires additional muscle activation in the lower limbs throughout the crossing steps. As such, information about an obstacle’s size may be needed at a different time than information about obstacle location. In the present study, we tested this prediction by instructing subjects to step over obstacles in a virtual environment viewed through a head-mounted display and manipulating the availability of visual information about the obstacle’s size. The obstacle’s location was always visible, but its size was not apparent until subjects reached a visibility window located at different points during approach. The size of the obstacle and timing of the visibility window varied between trials. Performance measures and gait parameters from an initial experiment suggest that information about an obstacle’s size is not necessary until just prior to obstacle crossing. As such, information about obstacle size may be picked up later than information about obstacle location in order to raise the feet on the basis of active adjustments to the gait cycle during crossing. We discuss how these findings support the broader theoretical claim that the use of visual information is constrained by the biomechanics of walking.
Meeting abstract presented at VSS 2015
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