Ergonomic Evaluation of Different Working Posture and Handle Designs of Mason Trowel during Wall Plastering Work based on Shoulder and Arm Muscle Activity

This study aims to identify the impact of the three ergonomically designed mason trowel handles at two working postures on the arm and shoulder muscles activation through experimental and subjective analysis. Prolonged usage, poor ergonomic design of trowels, and working at awkward postures results in Work-related Musculoskeletal Disorders (WMSD) among workers performing wall plastering task. Three mason trowels with different handle shapes were designed by modifying existing mason trowels and developed with 3D printing technology. Twelve student volunteers took part in this experimental study and simulated the wall plastering work at two commonly adopted working postures. Muscle activation and fatigue characteristics of five muscles on the arms and shoulder region were studied using Electromyography sensor (sEMG) sensors. Borg's CR-10 scale was employed to carry out the subjective analysis to find mean discomfort among the models. The results revealed that handle shape and working position have an influence on the shoulder muscle engagement and less effect on the arm muscles. Subjective analysis results revealed that Model B and Model C were rated with higher preference by the participants. Results have revealed that shoulder muscle is activated more and subjected high muscle fatigue while performing wall plastering tasks. Also, circular-shaped handles with varying cross sections and curved shape handles were rated as highly compared to wall plastering work. Findings from this study can be used for studying the relationship between mason trowel designs and working posture with muscle activation.