Analysis of the limits of automated rule-based ergonomic assessment in bricklaying

Physically demanding and repetitive tasks expose workers to work-related musculoskeletal disorders (WMSDs). Over the last few decades, various rule-based postural assessment systems have been developed and widely used to facilitate the measurement and evaluation of risks related to WMSDs in many industries. However, the applicability of rule-based assessment to tasks involving heavy material handling has not yet been examined. This study investigated the applicability of three rule-based assessment systems (RULA, REBA, and OWAS) to a bricklaying task. To achieve this goal, an automated assessment tool was developed to implement those systems on whole-body data sets consisting of static postures captured by wearable inertial measurement unit suits. The study demonstrates the use of this tool in assessing risk levels (grand scores) encountered by 43 masons during the laying of 16.6-kg concrete masonry units (CMUs) in a standard wall. Furthermore, the biomechanical analysis of the same data set was carried out and utilized as ground truth to evaluate those results. It was found that rule-based assessment may lead to erroneously inflated risk evaluation in heavy manual handling tasks. In contrast, biomechanical analysis provided sensitive risk evaluations that distinguish the different degrees of risk arising from different motion patterns while participants performed the same tasks. These findings suggest using biomechanical analysis as an objective and robust method to evaluate risks encountered in tasks involving heavy material handling.