A Facility for the Study of Pelvis and Trunk Displacements During Sitting Posture

Abstract

Abstract: Pressure sores are frequent in subjects who are paralysed because of spinal cord injuries and confined to wheelchairs: to prevent sores, these subjects must get used to frequently changing their posture. Useful information to investigate change characteristics may come through studying the behaviour of healthy subjects during long periods of sitting posture: to this aim, in the Department of Biomedical Engineering of Tel Aviv University, markers were applied to the trunks of subjects who were then filmed, while in the Department of Mechanics and Aeronautics of Rome University “La Sapienza” (DMA), angular potentiometers were applied to the base of the spine of subjects sitting on a chair where a pressure map sensor was positioned. In this paper a modification of the potentiometer device is shown: linear potentiometers are also applied to the base of the spine of the subjects; so, in addition to the relations among pelvis centre of pressure (COP) displacements, and trunk rotations, it is possible to find the relations between trunk translations and trunk rotations and between trunk translations and COP displacements; so all the characteristics of the movements of the pelvis and of the trunk at the base of the spine can now be investigated and compared. The results of the tests on 10 healthy DMA students following an established movement sequence are shown: there are particularly significant relations between trunk translations and trunk rotations in the sagittal plane, and between trunk translations and COP displacements in the frontal plane.