Working Posture and Muscle Tension according to Screen Position during VDT Operation

ABSTRACT

OBJECTIVE: To evaluate working condition in way of measuring working posture and muscle tension using the desktop personal computer and notebook personal computer having different screen height. METHOD: Seventeen healthy men performed wordprocessing task in three workstation desktop PC on the conventional computer table (DPC (on)); desktop PC under the 'inside' type computer table (DPC (under)); notebook PC on the table (NPC). The viewing distance and angle, head and neck angle, thoracic bending and trunk inclination were measured. Muscle tension of right posterior neck muscle, upper trapezius, sternocleidomastoid (SCM), and upper back muscle was also measured by integrated electromyogram (IEMG). RESULTS: 1) The viewing distance was the longest in DPC (under). 2) The lower the screen height, the more downward viewing angle and more flexed position in upper neck. 3) The posterior neck muscle tension was the lowest in DPC (on). 4) Stooped position was most frequently seen in NPC and the highest tension of posterior neck muscle and upper back muscle was shown in NPC. 5) In relation between postural analysis and muscle tension, muscle tension decreased with increasing backward reclining position, and the neck and thorax became more erect with increasing in viewing distance. CONCLUSION: These results suggest that the stooped posture was worst and most frequently seen in NPC. If neck flexion is avoided, DPC (under) position could lessen the visual and musculoskeletal problem. More Ergonomical study would be needed about working posture using computer.