Predicting shoulder musculoskeletal discomfort from worker anthropometry and workplane design in a repetitive task

摘要

A study was conducted to determine the effects of biodemographic, anthropometric, workplace and kinematic factors upon shoulder musculoskeletal discomfort (SMD). The study was performed in two phases. In the first phase the experiment was focused on gathering workplace, anthropometric and biodemographic factors, in addition to discomfort data. The second phase was conducted to gather the kinematic factors. Participants performed a mail-sorting task and at periodic intervals rated the perceived discomfort using a questionnaire. Four duty cycles (i.e., repetition rates) and five mailbox locations were evaluated. SMD was the dependent variable examined in this experiment. A total of sixteen independent variables were considered in this experiment. These variables were selected from four categories as follows: biodemographic (age and gender), anthropometric (height, weight, forward reach, midshoulder height, upper arm length and elbow to grip length), workplace (duty cycle, number of repetitions and mailbox location) and kinematic variables (movement time, elbow flexion, shoulder forward flexion, shoulder horizontal flexion and abduction/adduction angles). By using multiple regression techniques and statistical variable elimination methods it was determined that the best model to predict SMD included ten variables. The results show that from all the ergonomic variables evaluated, the kinematic variables played an important role in the percentage of the total variance explained by the regression models.