Low Back Disorder Risk in Automotive Parts Distribution

The purpose of this study was to characterize the low back disorder (LBD) risk in jobs found in automotive parts distribution centers. This descriptive study analyzed 53 jobs at 7 automotive distribution facilities in the Northern United States. Data were collected using the Lumbar Motion Monitor (LMM) and analyzed using the LMM LBD risk model. Historically, the LMM risk model, which was developed primarily through an analysis of manufacturing jobs, has used the peak load moment in the calculations. A secondary purpose of this study was to compare the difference in LBD risk estimates obtained using the peak versus the mean load moment in the analysis of these highly variable lifting jobs. Given that each lifting task may be a different weight item from a different location the sampling process was validated using split-test reliability coefficients. These were found to be 0.90. Results indicate that, on average the jobs in automotive parts distribution are moderately high risk (mean= 56%, s.d.= 11%), however, nearly half the sample had LMM LBD risk probability values greater than 60% mark that has been used by some as a cut point in defining “high” risk (Marras et al., 2000). On average, use of the average moment instead of the maximum moment reduced the LBD risk probability value by 7.4 percent (s.d.= 5.3%), however, the range included no difference up to 17 percent. Many of the jobs contain trunk motions that are associated with high LBD risk, however, many of these same jobs had relatively low lifting frequencies which moderated the risk estimates. It should be noted that for many of the jobs the LBD risk probability was at the medium level due to the travel time required between lifts. This kept the frequency of lifting in many of these jobs relatively low for distribution type work; for many jobs the liftrates were less than 60 lifts per hour. The liftrate potentially contributes 20 percent to the overall risk calculation in the model. This suggests that efforts to increase the pick rates and efficiencies in these jobs will be accompanied by increased LBD risk if done without accompanying ergonomic interventions.