THE EFFECT OF SHOULDER POSTURE ON PERFORMANCE, DISCOMFORT AND MUSCLE FATIGUE WHILE WORKING ON A VISUAL-DISPLAY UNIT

An investigation was conducted to determine the relationship between p osture and performance while working on a VDU, Twenty-one female subje cts performed a 20 min choice reaction time task in a within-subject d esign with shoulder flexion (0 degrees versus 30 degrees) and noise (5 5 dB versus 75 dB) as factors. Discomfort measures, electromyography ( EMG) measures and measures of performance including reaction time and percentage of errors were collected. The results suggested poorer perf ormance in the 30 degrees shoulder flexion posture compared to the 0 d egrees shoulder flexion posture (performance index F-1,F-20=3.95, p=0. 061). There was also significantly greater discomfort and fatigue, as indicated by EMG, in the 30 degrees shoulder flexion compared to 0 deg rees shoulder flexion (discomfort: F-1,F-20=99.30; p=0.0001 EMG: F-1,F -20=4.25, p=0.052). The results of this study provide the most direct evidence that the posture of VDU users can affect their performance at a task. A number of possible mechanisms for posture to affect perform ance are explored using the data. The utility of data showing the effe ct of posture on performance data is discussed in terms of financial m odelling to justify the cost of ergonomic intervention.