Effects of working posture and height on shoulder and spine loading during automobile repair tasks

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University of New Brunswick


Automobile mechanics are more likely to be injured at work compared to workers in some other trades. In the United States in 2011, 3.9 out of every 100 employees in the automotive repair industry suffered from some type of workplace injury or illness (Lopez-Arquillos, 2016). WorkSafe NB has recently announced the garage industry as their focus industry for the next couple of years in an effort to reduce reported injury claims. The purpose of this research was to investigate the biomechanical demand associated with tire changing of 16” tires while simulating jack and mechanical hoist options for raising the car. It was found that working at the height of the iliac crest may reduce exposure to increased deltoid activation and shoulder loading during loosening, lowering, and tightening tasks. Working at mid height reduced deltoid activation and shoulder flexion moment during all tasks excluding lifting. Shoulder moment, trunk moments, spine compression, and muscular activity of the forearm flexor, biceps brachii, anterior deltoid, and erector spinae were greatest during lowering and lifting tasks. Anterior deltoid activation and shoulder moment were significantly lower at the height of the iliac crest during loosening, lowering, and tightening tasks (p = 0.05). It was recommended that tire changing tasks be completed around the height of the iliac crest to reduce biomechanical loading of the shoulders, and cumulative loading of the spine. The study was the first to quantify physical demands associated with automobile tire changing.