Biomechanical analysis of the trunk during a material handling task performed by experienced and inexperienced subjects

Abstract

The aim of this study was to evaluate thoracic-lumbar movements and compare the performance of experienced and inexperienced subjects
during a manual handling task. Sixteen experienced subjects and 15
inexperienced ones took part in the study. A simulated task of lifting and
lowering 7 and 15 kg boxes was performed. A flexible electrogoniometer
was used to measure the thoracic-lumbar spine during the task. The software 3DSSPP version 4.1 was used to estimate the L5/S1 disk compression during tasks, and a Matlab routine allowed for analysing movement patterns, time to complete the task and spine posture while placing box. The coefficient of variation was applied to quantify the intergroup variability. A Manova 3-way and the Student t test determined the differences between variables. Results pointed to differences in postures: smaller amplitudes for flexion and higher amplitudes for extension were identified in experienced subjects when loads were placed, respectively, on lower and higher surfaces. Disk compression values of 2500N and 3500N for experienced subjects and 3000N and 4250N for inexperienced ones were found, while placing boxes with 7 and 15 kg, respectively. These results show that different movement strategies occurred between groups, suggesting that experienced subjects presented
more protective trunk movements.