An Investigation of Leaning Behaviors During One-Handed Submaximal Exertions with Extended Reaches

Abstract

OCCUPATIONAL APPLICATIONS The purpose of this study was to investigate hand leaning forces and the preferred leaning postures when completing tasks with various task hand locations, force demands, and effort directions. Twenty female participants completed a variety of different exertions with a leaning surface available. The hand leaning force magnitude changed as task hand location, force direction, and force level changed. These forces were significantly higher during pulling tasks and increased with increasing task hand load. The leaning hand height was slightly higher when task locations were at shoulder height, compared to the umbilical height. The findings are important, as current ergonomic tools neglect to consider that different task characteristics may change how and when a worker leans with their hands. These findings are of particular use to industry, as ergonomists now have representative forces and heights, to help guide leaning estimates during proactive risk assessments. TECHNICAL ABSTRACT Background: Leaning occurs in many automotive manufacturing tasks and provides various benefits to the worker. Leaning may allow for a more effective posture for task completion or reduce loading on the spine. Ergonomic assessments of tasks with leaning can be problematic because there is not sufficient data to predict leaning hand forces or the location of the leaning hand. Therefore, this study was completed to investigate leaning hand forces to help ergonomists make better predictions of how a leaning hand might be used during various industrial tasks. Purpose: The purpose of this study was to investigate hand leaning characteristics and the preferred leaning postures when completing tasks with constrained reaches. Methods: Twenty female participants completed exertions with 24 combinations of load (27.5 and 55 N), force direction (push, pull, and down), horizontal reach (95% and 120% of arm length), and vertical height (shoulder and umbilical height). A large leaning surface was available to use while completing the task. Results: The height of the leaning hand ranged between 106.6 and 116.3 cm across all conditions. The leaning hand force was affected by task hand location, force direction, and force demand. Leaning hand forces increased with increasing task hand load and ranged from 13.8 to 79.6 N of force. Task hand pulls had higher leaning hand forces compared to push and down exertion directions, regardless of task hand location or force demand. Conclusion: The findings of this study will be of particular use to industry as ergonomists now have representative leaning forces and heights to help guide leaning estimates during proactive risk assessments.