Differences in computer exposure between university administrators and CAD draftsmen Hsin-Chieh Wu, Yung-Ping Liu, Hsieh-Ching Chen * Department of Industrial Engineering and Management, Chaoyang University of Technology,168 Jifong E. Rd., Wufong Township, Taichung County 41349, Taiwan article info Article history: Received 15 June 2009 Accepted 12 March 2010 Keywords: Computer input Activity monitoring Exposure assessment VDT work abstract This study utilized an external logger system for onsite measurements of computer activities of two professional groupsdtwelve university administrators and twelve computer-aided design (CAD) draftsmen. Computer use of each participant was recorded for 10 consecutive daysdan average of 7.9 Æ 1.8 workdays and 7.8 Æ 1.5 workdays for administrators and draftsmen, respectively. Quantitative parameters computed using recorded data were daily dynamic duration (DD) and static duration, daily keystrokes, mouse clicks, wheel scrolling counts, mouse movement and dragged distance, average typing and clicking rates, and average time holding down keys and mouse buttons. Significant group differences existed in the number of daily keystrokes (p < 0.0005) and mouse clicks (p < 0.0005), mouse distance moved (p < 0.0005), typing rate (p < 0.0001), daily mouse DD (p < 0.0001), and keyboard DD (p < 0.005). Both groups had significantly longer mouse DD than keyboard DD (p < 0.0001). Statistical analysis indicates that the duration of computer use for different computer tasks cannot be represented by a single formula with same set of quantitative parameters as those associated with mouse and keyboard activities. Results of this study demonstrate that computer exposure during different tasks cannot be estimated solely by computer use duration. Quantification of onsite computer activities is necessary when determining computer-associated risk of musculoskeletal disorders. Other significant findings are discussed. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Prolonged computer use is positively correlated with work- related upper extremity disorders (Bergqvist et al., 1995; Schreuer et al., 1996; Matias et al., 1998; Jensen et al., 2002; Blatter and Bongers, 2002; Szeto et al., 2005). Video display terminal (VDT) users have reported pain in their hands, wrists and arms that exceeds pain in other body parts (Rempel et al., 1999; Sauter et al., 1991). Szabo (1998) determined that 21% of work-related carpal tunnel syndrome (CTS) cases were attributed to repetitive data entry. Jensen et al. (1998) demonstrated that musculoskeletal symptoms are more prevalent for the arm and hand operating a mouse than for the other arm or hand. Two studies conducted by the National Institute for Occupational Safety and Health (NIOSH, USA) identified a relationship between keyboard usage and cumulative trauma disorder (CTD) symptoms (Fagarasanu and Kumar, 2003). These studies suggested that percentage of time spent typing, typing speed, and force were factors likely correlated with CTDs. Factors implicated in the development of a CTD are insufficient recovery time, highly repetitive tasks, awkward posture and high force (Silverstein et al., 1996; Putz-Anderson, 1988). When these factors are combined, the risk of developing a CTD is high. According to a literature review by Fagarasanu and Kumar (2003), data-entry (keyboarding) risk factors associated with CTS were repetitiveness, typing speed, typing force, keyboard height, awkward postures, keyswitch make force and keystroke activation force. Fagarasanu and Kumar also determined that a marked ulnar deviation, wrist velocity, range of motion and percentage of maximal force applied to a mouse increase risk for CTS more in women than in men. High carpal tunnel pressure while dragging and pointing a mouse was implicated in increased risk of CTS in the hands (Keir et al., 1999). Laursen and Jensen (2000) demonstrated that double-clicking caused the highest muscular loading during VDT usage. Many human factor and occupational epidemiological studies have investigated the health effects of VDT operation on the musculoskeletal systems of users. However, Gerr et al. (1996) identified that these studies have methodological limitations, inconsistent results and limited conclusions. Gerr et al. suggested that objective methods * Corresponding author. Tel.: þ886 4 2332 3000x4255, þ886 937 083781 (mobile); fax: þ886 4 2374 2327. E-mail address: hcchen@cyut.edu.tw (H.-C. Chen). Contents lists available at ScienceDirect Applied Ergonomics journal homepage: www.elsevier.com/locate/apergo 0003-6870/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.apergo.2010.03.006 Applied Ergonomics 41 (2010) 849e856