Estimation of physical workload of the low-back based on exposure variation analysis during a full working day among male blue-collar workers. Cross-sectional workplace study

Markus Due Jakobsen,Emil Sundstrup,Mikkel Brandt,Roger Persson,Lars L Andersen

doi:10.1016/j.apergo.2018.02.019

Abstract

This study aims to quantify physical workload of the low-back using exposure variation analysis (EVA) during a full working day among blue-collar workers with manual lifting tasks. One hundred and ten male employees (39 warehouse workers, 27 operators, 24 postal workers and 20 slaughterhouse workers) with manual lifting tasks from 12 workplaces participated. The workers performed standardized box lifts using 5, 10, 20 and 30 kg before and after a working day. Muscular activity of the low-back was measured throughout the working day using surface electromyography (sEMG). Corresponding sEMG-values for 0–30 kg lifts were identified using linear regression. EVA at exposure levels corresponding to “lifting periods” of [1-5, 5-10, 10-20, 20-30 and >30] kg in time intervals [0–0.5, 0.5–1, 1-2, 2-5, 5-10, >10] sec was computed. Back inclination was measured using tri-axial accelerometers. Compared to the other job groups, the operators’ low-back muscles were exposed to more short duration “lifting periods” with varying loads and more frequent medium duration high load “lifting periods”, respectively. The operators also worked more with their back inclined (>30°, >60°, and >90°) than the remaining job groups. Nonetheless, more than 41% of the workers performed heavy “lifting periods” that exceeded Danish lifting guidelines. This EVA demonstrates that almost half of the blue-collar workers were exposed to heavy low-back loading which puts them at risk of developing musculoskeletal disorders and low-back injury. Operators are, in particular, exposed to more short duration and medium duration “lifting periods” with varying load compared to warehouse-, postal- and slaughterhouse workers.

Highlights

The consequences of musculoskeletal disorders (MSD) and workrelated injuries in terms of sickness absence, reduced work-ability and early retirement pose a huge burden on individuals, workplaces and societies across the world (Morken et al, 2003; Holmberg and Thelin, 2006; Bevan et al, 2009; Andersen et al, 2011)
The exposure variation analysis (EVA) showed that the operator's low-back muscles were exposed to more short duration lifts (> 0.5 s and 0.5–1 s) with loads varying from 1-20 kg and 5-20 kg, compared to the other job groups (Fig. 2)
The results from this study demonstrate that almost half of the bluecollar workers perform heavy lifting in a way that puts them at risk of getting a low-back injury or develop low-back pain (LBP)

Summary

Introduction

The consequences of musculoskeletal disorders (MSD) and workrelated injuries in terms of sickness absence, reduced work-ability and early retirement pose a huge burden on individuals, workplaces and societies across the world (Morken et al, 2003; Holmberg and Thelin, 2006; Bevan et al, 2009; Andersen et al, 2011). Translating data based on workers self-reports into recommendations for lifting limits is a difficult feat and typically associated with poor reliability and validity as a result of recall and response bias (Hansson et al, 2001; Stock et al, 2005; Barrero et al, 2009; Takala et al, 2010; Kwak et al, 2011). For this reason, and even if technical measurements are more expensive and time-consuming than self-reports, using the appropriate technical measurements to quantify exposure should, in theory, provide a more valid method for identifying physical risk factors (Prince et al, 2008; Innerd et al, 2015)

Objectives

Results

Conclusion