A three-dimensional approach to the calculation of foot clearance during locomotion

Planar analysis has traditionally been used for the measurement of foot cle arance during locomotor activities. In this paper, an improved three-dimens ional approach to clearance detection based on surface contour measurement and virtual point creation is described and validated. A reflective stylus, used as a contact digitizer, provided an accurate description of the outso le of the shoe with respect to shoe-mounted markers, and the position of th e shoe relative to the global reference frame was determined by conventiona l three-dimensional kinematic techniques as the subject walked. The geometr y of the environment was described in the same global reference frame, and the clearance distance between the shoe outsole and the ground was determin ed throughout the swing phase. Accuracy to within +/-1 mm was obtained with a surrogate shoe which had a flat outsole surface, while analysis of an ac tual shoe resulted in accuracy to within +/-2 mm due to uncertainty during digitization and deformation of the shoe under loading. (C) 1999 Elsevier S cience B.V. All rights reserved. PsycINFO classification: 2260.