A computational study of shoulder muscle forces during pushing tasks

Previous research into the biomechanics of pushing tasks focused on shoulder moment to measure operator shoulder stress, without employing a biomechanical model of the shoulder complex. The goal of this research was to explore the process of developing analysis and design tools that input easily measured parameters to quantify the stress of pushing tasks, suggest maximum acceptable loads for pushing tasks and suggest optimal handle heights and pushing styles. Shoulder loading analysis modules were used to produce a look-up table which allows ergonomists to estimate the percentage of maximum muscle force generated by the subscapularis muscle, which is considered to be a marker variable for increased risk of subacromial impingement syndrome. Two methods were developed to determine maximum acceptable pushing forces: a look-up table and an empirically derived equation. The second design tool was replaced by a design recommendation: push with a cart handle near waist height with arms extended.