Measurement of Postural Change in Trunk Movements Using Three Sensor Modules

This paper introduces a method of using 3-D accelerometers, gyroscopes, and an autoreset algorithm for tracking the trunk movements and estimating the regional trunk postural changes in the sagittal and coronal planes. Three sensor modules of the newly designed sensing system were attached onto the back of the skin surface at the levels of T1/T2, T12, and S1. The angular measurements from the sensor modules were used to estimate the spinal curvature changes of nine healthy subjects during their trunk movements. The measurements of the sensing system were found to be highly correlated with that of a Vicon motion analysis system. The correlation coefficients were found to be greater than 0.994 for dynamic tilting measurements and greater than 0.776 for trunk postural measurements; and the RMS differences were less than 1.5$^{\circ}$ for dynamic calibration and less than or equal to 4.5$^{\circ}$ for the estimation of trunk postural changes. This method could be considered as a useful way of quantifying the trunk postural information. With further developments in data logging and feedback mechanism, it can become a portable posture tracking and monitoring system for training those with postural deviations even during their normal daily activities.