Bending the tool and the effect on human performance: further investigation of a simulated wire-twisting task.

A previous experiment by the authors investigated the effect of the design of pliers on productivity. A simulated wire-twisting task performed at five heights between 10 inches above and 10 inches below elbow height formed the basis of the comparison. Pliers designed according to the American National Standard for long nose and long reach pliers were compared to bent-handled pliers designed at the Western Electric (WE) Co. The WE pliers, designed to reduce ulnar deviation during a wire-twisting task, resulted in productivity decrements between 1.4 and 17% across the five heights studied. The current experiment was a continuation of that study, adding orientation of the workplace in the sagittal plane as an independent variable. Wrist deviation in two planes were additional dependent measures, and the experiment was performed by female subjects with a mean age of 48.1 years. The results did not indicate a significant difference between productivity levels for the two pliers designs. Work height and work orientation, as well as their interaction, tended to have the strongest effects on productivity and wrist deviation. In general, productivity was inversely related to measures of discomfort and postural deviation.