Visual exteroceptive information provided during obstacle crossing did not modify the lower limb trajectory.

The roles of visual exteroception (information regarding environmental characteristics) and exproprioception (the relation of body segments to the environment) during gait adaptation are not fully understood. The purpose of this study was to determine how visual exteroception regarding obstacle characteristics provided during obstacle crossing modified foot elevation and placement with and without lower limb-obstacle visual exproprioception (manipulated with goggles). Visual exteroceptive information was provided by an obstacle cue - a second obstacle identical to the obstacle that was stepped over - which was visible during crossing. Ten subjects walked over obstacles under four visual conditions: full vision with no obstacle height cue, full vision with an obstacle height cue, goggles with no obstacle height cue and goggles with an obstacle height cue. Obstacle heights were 2, 10, 20 and 30 cm. The presence of goggles increased horizontal distance (distance between foot and obstacle at foot placement), toe clearance and toe clearance variability. The presence of the obstacle height cue did not alter horizontal distance, toe clearance or toe clearance variability. These observations strengthen the argument that it is the visual exproprioceptive information, not visual exteroceptive information, that is used on-line to fine tune the lower limb trajectory during obstacle avoidance.