The Alteration in the Center of Pressure and Duration Ratio of Stance Sub-Phases during Upslope Walking

Abstract

Upslope-walking is more challenging and therefore has a greater fall risk than level-walking. The current study aimed to investigate the difference in control strategy for stability between level and upslope walking using the center of pressure (COP) and the ratio of three sub-phases in stance phase (loading-response, mid-stance and push-off). Two hypotheses were tested: the excursion, range, and speed of the COP increases in the mediolateral and anteroposterior directions with slope grade; and the duration of the midstance phase increases with slope grade. Eleven male subjects walked on a level (0°) surface and upslope at 15° and 25°. The duration of the mid-stance phase was significantly greater in the 25° upslope-walking condition than that in the level and 15° upslope-walking conditions (both p<0.05). This result implies that the subjects adopted a different control strategy when walking upslope at 25° than when walking level and upslope at 15°. The range and speed of the mediolateral COP were larger in the 25° upslope-walking condition than those in the level and 15° upslope-walking conditions (p<0.05). This result indicates that a change in control strategy during upslope-walking at 25° can improve mediolateral stability. These findings imply that a transition grade exists between 15° and 25° where one can alter their control strategy to improve stability during upslope-walking.