The effect of shoulder posture on performance, discomfort and muscle fatigue whilst working on a visual display unit

An investigation was conducted to determine the relationship between posture and performance while working on a VDU, Twenty-one female subjects performed a 20 min choice reaction time task in a within-subject design with shoulder flexion (0 degrees versus 30 degrees) and noise (55 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 performance in the 30 degrees shoulder flexion posture compared to the 0 degrees 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 degrees 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 performance are explored using the data. The utility of data showing the effect of posture on performance data is discussed in terms of financial modelling to justify the cost of ergonomic intervention.