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Walkway surface heights and ground reaction forces

Falling is a leading cause of morbidity and mortality in the U.S. Several factors can contribute to injuries resulting from tripping, slipping and falling during locomotion such as surface condition, transitions and the degree of walkway evenness. Because walkway unevenness has been largely unexamined, the purpose of this study was to evaluate the extent to which gait kinetics change with uneven walkway surface heights. In this study, subjects walked at a constant velocity over a walkway, whose surface for various trials was positioned above, below, and level with respect to multicomponent force measuring plate. Ground reaction forces (GRF) were recorded from a single step when the subject stepped up or down onto the force plate during gait. Averaged trials from three step-up and two step-down heights were compared to level gait trials. GRF parameters included peak force components, center of pressure and temporal measures. Significant differences in GRF measures were found between the level condition and step-up heights >2.5 cm and step-down heights >-1.5 cm. No differences were found between the level condition and a step-up height of 0.7 cm. The results suggest that a walkway unevenness of >2.5 cm step-up and >1.5 cm step-down may contribute to initiating a trip, stumble or fall since the GRF are significantly altered with these conditions. However, negotiating a step-up of <2.5 cm or step-down of <0.7 cm produces gait kinetic measures similar to walking on a level surface, and therefore may not predispose one to a trip or stumble.