Dynamics and coordination of torso motions in human locomotion

Abstract

A model is presented which compactly expresses the magnitudes and phasings of torso motions and indicates the character of bipedal support and stabilization by foot placement. The model includes all of the principal inertial body components: upper torso (and head), both arms, lower torso, and both legs. In this study specific arm-thorax and leg-pelvis phasings are assumed, based on data. However, the possibility of other phasings is retained in the analysis. The analysis indicates that arm and leg swing are significant inertial influences, and must be included (somehow) in a dynamical characterization. The model retains all of the intuitive dynamical properties such as the inverted pendulum aspect of human support and effect of foot placement (lateral support point) for stabilization. The resulting expressions are actually quite simple, partly because of the small torso angular motion assumptions and partly because of fortuitious geometric and kinematic properties. The predicted phasings and the magnitudes are generally corroborated by data.