Abstract
Thirty-six subjects rated seven vertical and four horizontal positions after driving 25 screws at each of these work locations. The four horizontal work locations ranged from 13 to 88 cm and the seven vertical work locations ranged from 38 to 191 cm. Pneumatic tools (torque set to 3.2 Nm) with three varying shapes (pistol, in-line, and right-angle) were used to drive the screws into perforated sheet metal. Before rating each work combination with the Borg ten-point ratio rating scale, subjects were asked to imagine that they were an assembly line worker who was required to drive screws at that work location and with that particular tool for 8 hours. The work location/tool combination that received the lowest ratings of perceived exertion for the vertical surface were given after using the pistol tool to drive screws between 114 and 140 cm. Using the right-angle or the in-line tool to drive screws at distances between 13 and 38 cm received the lowest ratings of perceived exertion on the horizontal surface. The results compare favorably with predictions from biomechanics and anthropometric data.