Analysis of Aiming with Tools: Proprioception

Abstract

One of the major areas of interest in the field of ergonomics is the design of hand tools. Though considerable research has produced more user-friendly tools, there has been some reluctance to use them for some tasks. It is hypothesized that this reluctance on the part of the user may be partly due to the reduction of accuracy while using those handles. A pilot study employing twenty subjects (10 males, 10 females) was undertaken to evaluate three different grip angles, between the tool and handle axis, combined with four visual availability of the target conditions. Each subject was asked to aim at the center of the target under all the twelve test scenarios, with each subject performing ten trials in each scenario. The target was a touch screen monitor. The interface was a black screen background with the center indicated by a red cross-hair. The results of this study showed that the dependent variable, accuracy, was primarily effected by the angle of the of the handle grip with respect to the tool axis and by the visual availability of the target in a manual-aiming task. The tool with the least ergonomically correct wrist position yielded the best accuracy. As expected, the blind condition was the worst, but seeing the points that had been previously hit as additional visual feedback did not improve performance. The overall implication being that the most ergonomically correct tool might not lead to the best performance unless proprioception or feedback is taken into consideration. This has direct implications for tasks such as laparoscopic surgery where a long shafted tool is used with little visual feedback.