Relative importance of expertise, lifting height and weight lifted on posture and lumbar external loading during a transfer task in manual material handling

Abstract

The objective of this study was to measure the effect size of three important factors in manual material handling, namely expertise, lifting height and weight lifted. The effect of expertise was evaluated by contrasting 15 expert and 15 novice handlers, the effect of the weight lifted with a 15-kg box and a 23-kg box and the effect of lifting height with two different box heights: ground level and a 32 cm height. The task consisted of transferring a series of boxes from a conveyor to a hand trolley. Lifting height and weight lifted had more effect size than expertise on external back loading variables (moments) while expertise had low impact. On the other hand, expertise showed a significant effect of posture variables on the lumbar spine and knees. All three factors are important, but for a reduction of external back loading, the focus should be on the lifting height and weight lifted.

Practitioner Summary

The objective was to measure the effect size of three important factors in a transfer of boxes from a conveyor to a hand trolley. Lifting height and weight lifted had more effect size than expertise on external back loading variables but expertise was a major determinant in back posture.

Keywords:

• manual material handling
• lifting
• expert
• low back load
• ergonomic intervention
• training programs

Acknowledgements

The authors would like to give special thanks to the other members of the IRSST MMH Research group: Erik Salazar, Marie St-Vincent, Iuliana Nastasia, Sophie Bellefeuille and Maud Gonella. This research project was funded by the Robert-Sauvé Occupational Health and Safety Research Institute (IRSST) of Quebec. Thanks also go to the expert and novice subjects and the industries that participated in this project.