Non-invasive measurement of three dimensional joint angles: Development and evaluation of a computer-aided system for measuring working postures

Abstract

A new system was developed to analyze work posture in order to measure the three-dimensional body angles required as inputs to a biomechanical strength prediction model. This system was non-invasive and required no interference with work activities. Videotape was used at the job site to establish a permanent record of postural activity and a computer-aided digitization system was used to measure body angles in the laboratory.An experiment using five subjects and ten work postures was performed to investigate the nature and significance of measurement errors when using the new system. The results of this experiment revealed that, in general, subjects were able to distinguish different work postures; and that inter-subject bias was not significant. Measurement error was small for most joint angles and could be reduced further by enhancements to the system hardware. The system was found to be a useful tool for determining three-dimensional body angles when direct measurements are infeasible.