Analysis of the linear displacement of the head and trunk during walking at different speeds

Abstract

The displacement of points lying on the longitudinal axis of the upper part of the human body at head, shoulder and pelvis level was estimated in the three dimensions of space during level walking on a straight line at speeds ranging from 0.99 to 2.79 m s⁻¹. A stereophotogrammetric technique was used. Forty-one walking trials of five young male subjects with no apparent abnormalities of the locomotor system, were recorded. Harmonic analysis of the displacement functions was carried out. This permitted the identification of two superposed components of the motion pattern of the upper part of the body. One, described as intrinsic to the locomotor act in its essential form, showed characteristics that were remarkably constant both within and between subjects. The other, described as extrinsic, showed erratic features, possibly due to functional or anatomical asymmetries of the locomotor apparatus or to environmental disturbances. The identification of these two components of the motion pattern formed the basis for the definition of a standard average normal walking. Modifications of the motion pattern arising from variations in the speed of progression are identified and discussed also with the help of Lissajous's figures. Emphasis was given to the sources and magnitude of the inaccuracies with which the experimental and analytical results were obtained.