Changes in the temporal and distance parameters of gait evoked by negotiation of curbs

We report a study in which we examined the gait modulations performed by a group of healthy adults, naive to the purpose of the study, while walking across a curb under natural environmental conditions out of doors. Data were collected for step time and step length using a video camera and a 20m walkway. Location of foot position was achieved using a novel method to account for parallax and out of plane motion. The results obtained indicated that during both curb ascent and descent, subjects were able to predict accurately the need to make an adjustment to step length in order to avoid placing the foot in a potentially hazardous position on or near the curb. These step adjustments involved both lengthening and shortening the step as well as keeping it unchanged. In any case, the selection of strategy was apparently not influenced by the walking speed but was a function of the predicted foot position with respect to the curb. Also, the time at which the step adjustment was made appeared independent of the time to contact with the curb. These results suggest that, under natural circumstances, accurate planning for obstacle negotiation is made some distance before the obstacle.