Effects of speed and visual-target distance on toe trajectory during the swing phase of treadmill walking.

Gait kinematics have been shown to vary with speed and visual-target fixation distance, but their combined effects on toe trajectory during treadmill walking are not known. The purpose of this investigation was to determine the role of walking speed and target distance on vertical toe trajectory during treadmill walking. Subjects walked on a treadmill at five speeds while performing a dynamic visual-acuity task at both "far" and "near" target distances (ten trials total). The analysis concentrated on three specific toe trajectory events during swing: the first peak toe height just after toe-off; the minimum toe height (toe clearance), and the second peak toe height just before heel strike. With increasing speed, toe clearance decreased and the peak toe height just before heel strike increased. Only the peak toe height just after toe-off was significantly changed between the near-target and far-target tasks, though the difference was small. Therefore, walking speed and visual-fixation distance cannot be neglected in the analysis of toe trajectory. Otherwise, differences observed between populations may be attributed to age- or clinically related factors, instead of disparities of speed or target-fixation distance.