Effects of gender and reach distance on risks of musculoskeletal injuries in an assembly task

Abstract

This study investigated differences in elbow and shoulder flexion angles in an assembly task. The experiment involved ten subjects on a simulated assembly task that consisted of seventeen task elements. The locations of the components were at three distances from the subjects. Confidence intervals (90%) were estimated and large differences in risk levels were found when data were pooled from both males and females. Between gender comparisons of joint angles revealed that the male elbow angles were smaller than the females, but the male shoulder angles were greater than the females on average. A within-gender analysis found greater change in angles for the female group with an increase in task distance from the body. This was not the case for the males. This was explained with reference to a previous study that related anthropometrics to differences in joint angles. The shoulder was identified as a joint sensitive to small physical changes in the workplace layout that may make a task more awkward to reach. This was not the case for the elbow. Finally, it was noted that both directions of movement and initial hand location affected final elbow and shoulder joint angles for task elements. Relevance to industry Data is available in the form of anthropometric tables, reach range distances and proposed workstation heights for industry so that differences both between and within genders can be best accommodated for good ergonomic design of workstations. There is a need to supplement this data with information on the variability of induced upper limb joint angles for repetitive assembly tasks within normal reach so as to assist the optimum design of workstations and reduce the likelihood of injuries.