Continuous assessment of back stress (CABS): a new method to quantify low-back stress in jobs with variable biomechanical demands.

Jobs with a high degree of variability in manual materials handling requirements expose limitations in current low-back injury risk assessment tools and emphasize the need for a probabilistic representation of the biomechanical stress in order to quantify both acute and cumulative trauma risk. We developed a hybrid assessment methodology that employs established assessment tools and then represents their evaluations in a way that emphasizes the distributions of biomechanical stress. Construction work activities in the home building industry were evaluated because of the high degree of variability in the manual material handling requirements. Each task was evaluated using the Revised NIOSH Lifting Equation, The University of Michigan Three-Dimensional Static Strength Prediction Program, and the Ohio State University Lumbar Motion Monitor Model. The output from each model was presented as time-weighted histograms of low-back stress, and the assessments were compared. The results showed considerable differences in what were considered high-risk activities, indicating that these 3 assessment tools consider the risk of low-back injury from different perspectives. The time-weighted distribution aspect of this methodology also contributed vital information toward the identification of high-risk activities. These results illustrate the necessity for more advanced low-back injury risk assessment techniques for jobs with highly variable manual materials handling requirements.