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

Planar analysis has traditionally been used for the measurement of foot clearance during locomotor activities. In this paper, an improved three-dimensional 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 outsole of the shoe with respect to shoe-mounted markers, and the position of the shoe relative to the global reference frame was determined by conventional three-dimensional kinematic techniques as the subject walked. The geometry of the environment was described in the same global reference frame, and the clearance distance between the shoe outsole and the ground was determined 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 actual shoe resulted in accuracy to within +/-2 mm due to uncertainty during digitization and deformation of the shoe under loading. (C) 1999 Elsevier Science B.V. All rights reserved. PsycINFO classification: 2260.