Modeling of Shoulder and Torso Effort Perception in Manual Tasks Kyunghan Kim, Bernard J. Martin, Clark R. Dickerson and Don B. Chaffin Proceedings of SAE Digital Human Modeling for Design and Engineering Conference, Munich, Germany, June 18-22, 2002. While biomechanical motion simulation models predict how a body segment moves in space and how much force is exerted by muscle groups in work tasks, it is still necessary to determine the subjective effort a person perceives, since it represents an integration of the physical demand of the work. Optimization of the workspace and minimization of risk injury can benefit from effort perception. The present study attempts to develop statistical models of perceived effort at the shoulder and torso levels, associated with load manipulation with one or two hands. The motions started from a home location and progressed toward one of twenty-two target shelves distributed around the subjects. Perception of effort at the shoulder and the low back was rated using a ten-point visual analog scale. Calibration of perception was based on training using a set of predetermined effort levels expressed by a percentage of the respective maximum voluntary contractions. A total of 2,551 ratings were obtained from twenty subjects. Both stepwise and standard least square regression methods were used to identify significant factorial effects and their respective coefficients. The regression models include input parameters such as standing or seated posture, one or two handed lifting, target position, demographic and anthropometric measures, and torso or shoulder maximum strength levels. The models predict perception of effort with r-square coefficients of .60 and .66 for shoulder and torso effort, respectively. The model outcomes were also compared to statistical models of external dynamic moments at the shoulder and low back. abs2002_07