Abstract
When walking over complex terrain, humans use visual information about the upcoming ground surface layout to exploit the passive physical forces inherent to bipedal locomotion. We previously showed that visual information about potential target footholds for an upcoming step is critical for control during the end of the preceding step. Visual information about target position presented during this critical control phase was sufficient for subjects to accurately step to a target, while the same information presented before or after the critical phase resulted in less accurate foot placement. Although visual information about target position is not essential once the step to that target is initiated, it remains unclear whether humans are capable of using such information to improve stepping accuracy following a perturbation during that step. Reynolds and Day (2005) demonstrated that, when taking a single step, participants rapidly respond to changes in target position while the foot is in flight. However, it is not known whether humans exhibit such active corrections during continuous walking over longer stretches of complex terrain, when locomotion is largely under passive control. In the present study, subjects walked along a path of irregularly spaced targets projected onto the ground while their movements were recorded with motion capture. As subjects approached targets, each target briefly disappeared and then reappeared. On a subset of trials, the location of one of the six targets was perturbed in either a medial-lateral or anterior-posterior direction while invisible. Subjects’ responses to the perturbation depended on the timing of visual information during that step. Discussion focuses on the contributions of active control, to respond to perturbations during the swing phase, and passive control, to efficiently adapt the gait cycle to upcoming terrain.
Meeting abstract presented at VSS 2015