Comparison of activation and change in the upper trapezius muscle during painful and non-painful computer work.

[Purpose] Activation and changes in parts of the upper trapezius muscle during painful and non-painful computer work were compared. [Subjects] Ten male computer workers were recruited. [Methods] Surface electromyography was used to compare upper trapezius muscle activation and changes (difference between minimum and maximum activation) during painful and non-painful computer work. [Results] Mean normalized upper trapezius muscle activity did not differ between the "feel-pain" and "non-feel-pain" muscle sections. The mean change in upper trapezius muscle activity in the feel-pain section decreased significantly compared to the non-feel-pain section. [Conclusion] Measuring changes in the activity of muscle sections was useful to study static and sustained muscle stress during computer work.