Simultaneous measurement of trunk orientation and centre of pressure for postural stability evaluation

Human balance control system allows people to independently perform acts of daily living and to avoid falls that can cause injuries and hospitalization. Aging or various pathologies may cause disorders in the balance system and result in wide variety of problems and generally decreased quality of life. Researchers and health professionals therefore strive to develop effective methods and instruments for prompt diagnosis and rehabilitation of balance disorders. A common approach used to detect balance problems in scientific studies and clinical applications is to analyze various parameters of postural stability gathered during quiet stance. This paper presents an experimental setting for postural stability evaluation composed of two independent systems. A commercial force platform (Ecowalk) and a sensor node with multiple inertial and magnetic sensors are combined to simultaneously measure trunk orientation and center-of-pressure (COP) during quiet stance. A preliminary study with 8 healthy subjects was conducted in order to test the system functionality. Trunk orientation and COP were measured in four different conditions for every subject as they tried to maintain steady upright position. The area of trunk sway trajectory and COP variability were calculated from orientation and force platform measurements. The goal of this study was to explore whether use of the created experimental setting can provide a measure of two different biomechanical properties related to the balance control system during quiet stance trials. The initial results are promising as they have shown consistency in both variables during trials in different conditions, but further measurements with more subjects are needed for stronger conclusions.