AN INVESTIGATION OF LEANING BEHAVIOURS DURING ONE-HANDED SUBMAXIMAL EXERTIONS WITH EXTENDED REACHES

Abstract

<p>The purpose of this study was to investigate leaning behaviours when completing tasks with constrained reaches. A logistic regression was developed, with the input of individual subject anthropometry and specific task characteristics, and the resulting model was able to provide a very accurate prediction of when an individual would lean. The inputs to this model give insight into what factors are important in the decision making process when a worker chooses whether lean. The task hand locations with the longest reaches resulted in the most frequent choice to lean. Leaning appears to be particularly common, and important, with long reaching and pulling tasks that can reduce task hand shoulder and trunk loads and improve balance, while allowing the worker to get closer to the task. Leaning hand forces were highest during pulling tasks. These findings are very important to document, as current ergonomic tools neglect to consider that different task characteristics may change how, and when, a worker leans. Even when only the direction of the task hand force was changed, leaning hand forces differed significantly. In this study, leaning hand height was slightly higher for the shoulder height, when compared to the umbilical height, task hand locations. The average height of the leaning hand did not vary considerably and ranged between 106.6cm to 116.3cm, depending on the condition. The leaning hand force magnitude changed as task hand location, force direction and force level changed. Leaning hand forces increased with increasing task hand load. Task hand forces in the push direction were higher compared to push and down exertions, regardless of task hand location or task hand load. The findings from this study are of particular use to industry as ergonomists now have representative forces and heights, to help guide leaning estimates during proactive risk assessments.</p>