Effect of ergonomic design changes in hand tools on physiological cost and subjective ratings

Users of hand tools expect that tools after ergonomic changes in design will require less muscular activity and cause fewer musculoskeletal disorders than conventional tools. Reports on evaluation of ergonomic design changes in hand tools are controversial. In this study, we measured the effect of changes in tool design with physiological cost of performance and subjective ratings in a simulated setting. We determined physiological cost of performance by measuring muscle activity of the right and left forearm (flexor carpi ulnaris) with electromyography. We collected a questionnaire with subjective ratings before and after each experimental task. Before the tests, ergonomically reconfigured hacksaws received better rating scores than original hacksaws. However, we found no differences in subjective ratings of the hacksaws after the tests. In addition, electromyographic activity did not show any significant differences between the original and modified tools.