Do Handle Design and Hand Posture Affect Pointing Accuracy?

Abstract

The design of ergonomic tools has focused on reducing the awkward wrist angles during tasks. However, anecdotal evidence shows that the adoption of ergonomic tools has been slow. This may be due, in part, to the ergonomic handles reducing accuracy of the task performed. A pilot study employing 20 subjects (9 men, 11 women) was undertaken to evaluate 4 handles, with two handles being used both in a pistol-grip and an inline-grip. All handles were evaluated while either seeing the target or blindfolded and either using the index finger extended as a guide or not. Each subject performed 24 total trials, which consisted of aiming at a sheet of vertically mounted A3 paper. The center point was marked and positioned such that the subject, when holding a pistol grip tool, had an adducted shoulder, a right angle at the elbow and a neutral wrist position. Each subject was asked to aim and puncture 10 holes in each target paper at a fixed pace. The results of the pilot study show that the dependent variables of the vector distance from the origin and the vector distance from the centroid of the points is affected primarily by the sight condition, but that the handle orientation with the inline condition was significantly better than the pistol grip for accuracy. In addition, the main effects of gender and tool type were significant for the dependent variable of the vector distance from the centroid. The overall implication is that the most ‘ergonomic’ handle may not yield the most accurate cluster or grouping when pointing and that handles held in an ergonomically awkward wrist posture (average 23° ulnar deviation).