The effects of typing skills on EMG activity and discomfort on neck and upper extremities

Abstract

Work-related musculoskeletal disorders (WMSDs) are common in computer users. More head, neck and upper limb movements can be observed in non touch typists than the other. This may be a cause of WMSDs. This study compared electromyographic activities (EMG) and discomfort (by using visual analog scale (VAS)) among healthy female touch and non touch typists.Two groups of typists comprising 21 touch typists and 20 non touch typists were voluntarily performed a continuous typing task for 240 minutes. EMG activities of upper trapezius, anterior deltoid and splenius capitis muscles and VAS at neck, shoulder and arm areas were recorded every 40 minutes. Individual workstation was set and word counts and errer typing rate were also recorded. Nomalized EMG (using maximum vouluntary contraction (%MVC)) was used to allow comparisons between groups. Percentage of MVC of anterior deltoid in the touch typist group was significantly higher than the non touch typist group (8-9% vs. 5.4-5.5%) at minutes 40, 80 and 160. In touch group, %MVCs significantly increased from minute 5 to 240 at anterior deltoid (8.04% vs. 10.80%) and splenius capitis (15.03% vs. 20.63%). In non touch group, % MVCs significantly increased from minute 160 to 240 at upper trapezius (7.38% vs. 8.59%) and from minute 5 to 240 at splenius capitis (20.71% vs. 22.89%). The percentages of error in the touch typist group was significantly higher than the non touch typist group (0.3% vs. 0.15%) during period 0-40 minutes. VAS in the non touch typist group were significantly higher than the touch typist group in neck (3.19 cm. vs. 2.10 cm.) and right shoulder (3.49 cm. vs. 2.18 cm.) at minute 240. Moreover, word counts significantly decreased over times. After typing for 40minutes, percentage of error in touch typist group significantly decreased when compared to that at the start. In addition, VAS at studied areas significantly increased over typing time in both groups. The study demonstrated that touch typists had advantage in discomfort and % MVC of upper trapezius. Therefore, touch typing practice should be recommended to novice typists.