Supermarket checker motions and cumulative trauma risk

The relationship between specific motions and symptoms consistent with upper extremity cumulative trauma disorders (UECTDs) was investigated in 50 supermarket checkers. Each completed a questionnaire concerning UECTD symptoms; four composite symptom indices were derived: any arm symptoms, hand-wrist-lower arm (S-DIST), upper arm, and symptoms specifically associated with carpal tunnel syndrome (S-SPC). Each participant was videotaped on at least two occasions while performing checking work. Analysis of these tapes assigned each subject a composite motion index for each of the following motions: wrist flexion, wrist extension, body (lumbar) flexion, pronation, grip type, and tendency to lift objects. "Positive" symptom status was defined by a score in the upper quartile for the symptom index. Relationships between an individual's motion indices and symptom indices were analyzed by determining the percent of subjects "positive" for symptoms in each quartile of motion index, by rank correlation, and by regression of symptom scores on principal components of motions. Trends toward relationship of wrist flexion and extension, lumbar flexion, and pronation with S-DIST and S-SPC were noted. Principal components regression confirmed that extension and flexion were related to these two symptom outcomes. This study suggests that postural loading can be determined on an individual basis in a meaningful fashion and that interventions that decrease such loading may be beneficial. It supports the role of certain repetitive motions as causes of UECTD symptoms.