Evaluation of postural risks and joint reaction forces during wall construction tasks

Background: Work-related Musculoskeletal Disorders (WMSDs) are a prevalent issue in wall construction tasks due to repetitive movement and awkward postures. The current study aimed to evaluate the postural risks and joint reaction forces (JRFs) of the shoulder, elbow, and neck joints during wall construction tasks performed at 0 cm (foot) and 77 cm working heights. Methods: Twelve male students (age: 21.83±1.27 years) performed four simulated construction tasks. Actual body movement data were captured with Inertial Measurement Unit (IMU) sensors and processed in the AnyBody Modeling System via a 3D musculoskeletal (MSK) model. The Rapid Upper Limb Assessment (RULA) method was used to evaluate the postural risk level. The joint reaction forces were calculated by inverse dynamics simulation and analyzed using a two-way ANOVA. Results: Working at 0 cm height resulted in high RULA scores of 7 (very high risk) during mortar scooping and picking up the brick. Working at 77 cm height, all tasks had modal and median RULA scores of 4, indicating lower postural risk. ANOVA results showed highly significant main and interaction effects of working height and tasks on shoulder, elbow, and neck JRFs (all p<0.001). Height exhibited exceptionally large effect sizes on shoulder (partial η² = 0.98), and elbow (partial η² = 0.92) joints. Conclusions: Therefore, a working height approximately midway between the worker's knee and waist heights (averaging 77 cm) effectively minimizes both postural risk and biomechanical joint loading during wall construction tasks.