Quantification of Wrist Motions during Scanning

Abstract

A laboratory study was performed to help assess the risk of cumulative trauma disorders (CTDs) associated with the use of scanners in the grocery store environment. In this study experienced and inexperienced cashiers scanned a set of 12 standard grocery items using 19 different combinations of scanners, scanner orientations, and check stands. The motion characteristics of both wrists in three-dimensional space were documented and used as dependent measures of performance. These motions were compared with wrist motion benchmarks of high-and low-risk wrist accelerations. It was found that, in general, scanning motions are of sufficient magnitude to contribute to CTDs of the wrist. It was also found that wrist motion characteristics were greatly influenced by the different combinations of scanners, scanner orientations, and check stand designs. It was concluded that the "front-style" check stand minimizes potentially injurious wrist motions because it permits the checker to split the scanning task between the two hands. The type of scanner and scanner orientation that minimized potentially injurious wrist motions was much more unique to the individual workstation condition. Additionally, it appears that scanners perceived by the checkers as needing fewer wrist deviations, such as those with slanted windows, also minimize wrist motions. The implications of these findings for the ergonomic design of the workplace are discussed.