EFFECTS OF OPTIC FLOW ON THE KINEMATICS OF HUMAN GAIT - A COMPARISON OF YOUNG AND OLDER ADULTS

This experiment studied the effect of imposed optic flow on human loco motion. Six young and 6 older adults were exposed to various patterns of optic flow while walking in a moving hallway. Results showed few ca ses of impaired postural control (staggers, parachute reactions). No f alls were recorded. Kinematic patterns of gait were altered when visio n was absent or inconsistent optic flow was presented: Ninety two perc ent of the subjects' mean step velocity differed from their step veloc ities under normal vision. Compared with imposed central flow, periphe ral optic flow was not dominant in inducing kinematic changes. Charact eristic gait profiles were obtained, depending on flow direction. Glob al backward flow tended to slow down step velocity, whereas subjects' step velocity increased during conditions of forward flow. The results suggest that subjects attempted to match their own walking speed to t he velocity of the moving visual scenes. It is concluded that in an un cluttered environment, imposed optic flow has a modulating rather than a destabilizing effect on human locomotion.