The effects of using a single display screen versus dual screens on neck-shoulder muscle activity during computer tasks

The present study compared the effects of using one versus two display screens on cervical muscle activity of computer users. Healthy pain-free university students were recruited (11 males and 11 females), and surface electromyography in bilateral cervical erector spinae and upper trapezius (UT) muscles was measured. Each subject performed standardized text editing tasks for 15 min using a single screen and dual screens in a randomized order. In the dual screen condition, the primary screen was placed directly in front while the secondary screen was angled to the right of the user. Significant reductions of the 50th and 90th percentile amplitudes, representative of dynamic muscle loading, were found in the right UT muscle for dual screen condition. The 10th percentile muscle activity was similar in all muscles in the two conditions. These results suggest that viewing dual screens may be associated with different postural muscle activity compared to single screen.