Postures and Movements of Upper Arms and Upper Back During Box Handling in Real Setting

Considering the lack of studies assessing biomechanical exposure during manual material handling (MMH) in real work environment, the aims of this study are: (1) describing postures and movements of the upper back and upper arms during MMH performed in a regular workday in a real setting; (2) comparing postures and movements according to height level of the MMH; and (3) investigating the relationship between postures/movements and the workers’ experience. Fourteen workers (28.14 ± 6.73 years) from the distribution sector of an automotive factory were evaluated during four hours of their regular work. Three workers who presented more than five years performing MMH tasks were considered as expert (6.33 ± 0.57 years of experience in MMH tasks). Eleven workers were classified as novices (1.24 ± 0.78 years). Postures and movements of upper back and upper arms were measured using inclinometers. APDF percentiles (10th, 50th, and 90th) were obtained for angles and angular velocities. All data were descriptively analyzed and a one-way ANOVA was performed in order to compare biomechanical exposure during MMH tasks performed in three different, and most adopted, heights (floor, chest and shoulder levels). Pearson correlation test was applied to investigate the association between experience and biomechanical exposure variables. Alfa level was set at 0.05. In general, the descriptive analyses showed no expressive difference between expert and novice workers. Significant statistical differences in upper back and upper arms posture and movement among the three most frequent handling heights were found. Moreover, there was a positive and significant correlation between workers’ experience and humeral elevation. Despite the limited number of workers, we could evaluate what in fact happen in real settings. We believe that the evaluation of larger samples would demonstrate differences between expert and novice workers also in real settings, as we could observe a tendency of safer strategies among experienced workers. The challenge is finding larger groups of workers doing MMH tasks considering the lean production systems.