The effect of trunk flexion angle and anthropometric dimensions on the accuracy of the allowable weight limits in pilot study

Iranian lifting guidelines are used as a risk assessment tool to prevent back pain in various industries. It is believed that the tools and methods used for the assessment should be simple and yet accurate.Given that this guideline adopted the American Conference of Governmental Hygienists (ACGIH) threshold limit values (TLVs) for lifting as allowable load limits and the accuracy of the allowable weight values has not been investigated. The objective of this study was to investigate the effect of trunk angle and anthropometric dimensions on the accuracy of the allowable weight limits.
In this study, 15 workers who had experience in manual handling were asked to perform lifting tasks in accordance with the Iranian guidelines. The subjects’ anthropometric and trunk inclination angles were recorded using a triaxial accelerometer (inclinometer) for each task, and the compressive forces were estimated using 3DSSPP and then compared with NIOSH’s recommended limits (3400N).
The results showed that among 25 tasks, the mean trunk angle of 13 tasks was between 90 and 130 degrees.
Statistically, considering a standard deviation above the determined mean, the average compressive forces estimated for 9 tasks were greater than NIOSH recommendation (3400).
In most tasks, vertical height and horizontal distance of external loads from the body leads to awkward postures that can be the main reasons for increased compressive force. Lack adaption some anthropometric measurements result in increased mechanical loads on the back. Therefore, it seems that the limit values for Iranian lifting guideline are not sufficiently accurate to assess the risk of back injuries and needs to be reviewed.