Can Visual Discomfort Influence on Muscle Pain and Muscle Load for Visual Display Unit (VDU) Workers?

In three different prospective epidemiological studies, correlation between visual discomfort and average pain intensity in the neck and shoulder, were 0.30<r<0.72 for VDU workers. In the first study, correlation between visual discomfort and pain in the neck and shoulder was 0.30<r<0.40. In the second study, visual discomfort was related to neck pain, (r=0.40, p=0.003). In the third study, visual discomfort correlated to neck pain (r=0.69, p=0.000) and shoulder pain (r=0.72, p=0.000). In order to study more in detail the correlation between visual stress and muscle load, a laboratory study was carried out. Visual stress was induced by the size of characters on the screen (8 points and 12 points Times New Roman) and the luminance levels in the surroundings of the screen (between 1500 and 2300 cd/m2) versus (between70 and 100 cd/m2). The results showed that the smallest characters 8 points and the highest luminance levels had no significant influence on the muscle load in neck and shoulder regions. However, the productivity was significant lower when using the 8 points characters compared with 12 points. There was also a tendency to an increase in the number of errors made.

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