Direct measurement of the centre of mass location in walking persons

Abstract

The movement of the whole body centre of mass (COM) is the best single descriptor of the movement of the entire human body. To date however, only indirect or derivative based methods have been used to estimate COM movement in human walking. In this study a direct COM location measurement system, comprising an adapted reaction-board technique consisting of a board supported by four load-cells, is described for determining COM location in walking human subjects. Life-sized projections of subjects in various stride positions are used to place subjects into recumbent static walking positions. Multiple static measurements are used to estimate dynamic COM movement. Data of COM oscillation on six male subjects (age 20 - 23 years) walking at 4 km.h^-1 on a motorised treadmill are presented. These data are the first direct measurements of COM oscillation in walking humans over an entire stride. Data found using other, less direct methods are not dissimilar to the data obtained for COM oscillation in this study (median vertical and anteriorposterior COM oscillation during walking 4.1 cm and 5.4 cm respectively, while median COM height was 99.3 cm above the treadmill surface over one stride duration). In addition, we were unable to detect a significant relationship between the magnitude of vertical or horizontal (forward-back) COM oscillation and stature in our subject group (R ²<0.1; p>0.5).

South African Journal for Research in Sport, Physical Education and Recreation Vol. 27(2) 2005: 57-68