Measuring lumbar motion in industry, utilizing the lumbar motion monitor

Abstract

Understanding the relationship between trunk motion, workplace factors, and the probability of incurring an occupationally related low back disorder (LBD) continues to be a challenging problem for ergonomists. To begin to solve this problem, previous studies have documented the trunk motion of a wide range of industrial jobs, but none have focused solely on the trunk motions observed in highly dynamic, high frequency manual material handling (MMH) jobs. A study was performed to quantitatively measure and document the E3-dimensional trunk motions of high frequency MMH jobs in industry using the Lumbar Motion Monitor (LMM) from Chattanooga Group, loc. Five jobs were analyzed with five different workers in each job. The range of motion observed for the sagittal plane, side bending plane, and rotational plane was -49 to +66 degrees, -34 to +29 degrees, and -31 to +34 degrees respectively. The average velocity for the three planes was 16.5/̊s, 9.3/̊s, and 10.9/̊s respectively. The average maximum velocity for the three planes was 186/̊s, 77/̊s, and 121/̊s respectively. The average maximum acceleration for the three planes was 1314/̊s² 561/̊s² and 752/̊s² respectively. A secondary purpose of this study was to evaluate the LBD risk model incorporated into the LMM Industrial Analysis software as a ranking tool for prioritizing jobs for interventions. This was accomplished by ranking the five jobs according to the risk model and comparing the ranking to a ranking based on the 1998 back injury incidence rates. The Spearman correlation coefficient for the comparison was -0.4. The results of this study document the magnitude of trunk motions that an MMH worker might be asked to perform, indicate the LBD risk model incorporated into the LMM Industrial Analysis software does a poor job of ranking jobs according to back injury incidence rates, and provide usability comments related to the LMM.