Thls study was designed to assess muscle tensions while working at a YDT workstation with surface electromyography (SEMG).

Variables texted were desk height, monitor positon on the desk, distance from edge of the desk to the keyboard. Eleven female volunteers working in the tele-com munication company were seated at an ergonomically adjusted workstation. They were assigned to a task of typing for 5 minutes and were given a 10 minutes resting with hands in their lap. For the initial experiment, the desk height was fixed to standard desk height(65.0 cm) recommended by ANSI and latter adjusted to a higher desk height (72.8 cm) for this study such that the subjects experienced slight elevation of shoulders. The monitor position initially at the center on the desk and latter left site of the desk (45o from monitorneck axles). The keyboard was positioned to an optimal distance (15 cm from the desk edge) and an abnormal distance (30 cm). Five muscle groups (paraspinal muscles, upper trapezium muscle, supraspinatus muscle, infraspinatus muscle, and rhomboid muscle) were selected for the study. The data of SEMG were analyzed by 2x2x2xs mixed factorial design.

The results were as follows: 1. SEMG activity recorded from the paraspinal muscles were significantly higher when the angle of the monitor adjusted to 45 degree from the center of the desk.. 2. SEMG activity recorded from the upper trapezius/supraspinatus/infraspinatus muscles were significantly higher when the hight of the desk was elevated from the recommended height.3. SEMG activity from the rhomboid muscle showed no significantiy difference in all test conditions.

The results of thls study confirm that the helght of a VDT workstation and the angle of the monitor are risk factors of upper extremity cumulative trauma disorders. Also SEMG would be useful for measuring muscle activities during workstation assessment.