An evaluation of a supermarket bagging task using a wrist motion monitor
Cumulative trauma disorders have become common among workers in industry. Grocery stores are an industry with one of the highest number of repeated trauma illnesses. Checkout departments have a rate of musculoskeletal injuries two to three times higher than other supermarket departments.
The primary objective of this study was to quantify the wrist motions required to bag groceries. Subjects participated in the laboratory or in the supermarket. The wrist motions included wrist deviations, velocities, and accelerations for flexion-extension, radial-ulnar, and pronation-supination deviations. The dependent variables were handle type and object location. A wrist motion monitor designed at Ohio State University was used to quantify wrist posture and movement.
Objects with finger-thumb handle couplings required more extreme ulnar deviations, more extreme pronations, greater wrist velocities for pronation-supination deviations, and greater wrist accelerations for pronation-supination deviations than did other objects. When comparing soft and solid objects, or round and square objects, there were few differences in wrist positions, velocities, or accelerations. Objects with 10-cm wide hand couplings required more extreme flexion, larger ranges of movement for radial-ulnar deviations and pronation-supination deviations, and greater wrist velocities in the radial, ulnar, and pronation directions than did 5-cm wide objects. The right and front locations required more extreme positions than did the left and back locations. Subjects participating at the supermarket site picked up objects with greater wrist velocities and accelerations than those in the laboratory; conversely, wrist positions were not affected by site. Because finger-thumb and 10-cm wide hand couplings required larger wrist deviations and greater velocities, these objects may pose a greater risk to the bagger of developing cumulative trauma disorders.