A study of biomechanical factors associated with computer mouse use in symptomatic and asymptomatic office workers

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A study of biomechanical factors associated with computer mouse use in symptomatic and asymptomatic office workers


Author: Lin, King-mo Joseph
Title: A study of biomechanical factors associated with computer mouse use in symptomatic and asymptomatic office workers
Degree: M.Sc.
Year: 2008
Subject: Hong Kong Polytechnic University -- Dissertations.
Wrist -- Mechanical properties.
Computers -- Physiological effect.
White collar workers -- Health and hygiene.
Department: Dept. of Rehabilitation Sciences
Pages: xii, 129 leaves : col. ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2232414
URI: http://theses.lib.polyu.edu.hk/handle/200/4865
Abstract: With widespread use of computer and incorporation of graphical user interface in most software packages, the computer mouse has become a very important input device in daily office work. Prolonged and intensive use of the mouse has been reported to contribute to work-related neck and upper limb disorders. Previous research has demonstrated that neck-shoulder muscles such as upper trapezius displayed consistent differences in muscle activities between symptomatic and asymptomatic computer users. These muscle activity differences were thought to be an important mechanism in musculoskeletal disorders. Up to date, there is still lack of controlled experiment investigating biomechanical parameters in wrist/hand region in persons with musculoskeletal disorders. Moreover, speed and precision stress are commonly encountered by office workers with use of computer mouse. Nevertheless, past research evidence of these two demands is mixed, and has only concentrated on healthy subjects. The present study compared the forearm muscle activities and wrist kinematics in persons with mouse-related wrist/hand musculoskeletal symptoms (1 males 9 females) and symptom-free controls (8 males 2 females), when they performed standardised mouse tasks. Each subject performed 4 multidirectional mouse clicking tasks with: (1) High Precision and Low Precision, (2) Fastest Speed and Constant Speed. Surface electromyography (EMG) of right flexor carpi ulnaris (FCU), flexor carpi radialis (FCR), extensor carpi radialis (ECR) and extensor carpi ulnaris (ECU) were measured and compared for median activities as well as the difference between peak and static activities (APDF range). Radio-ulnar deviation angles of the right wrist were measured by electrogoniometer, and presented as median wrist joint position and extent of radio-ulnar movement range. Other dependent variables included task performance measures and subjective discomforts. Results showed that the Case Group exhibited higher median muscle activities than the Control Group in all 4 muscles in all tasks. In general, the median muscle activities in the Case Group were about 1.7% to 5% MEMG greater than the Control Group. Three-way mixed model MANOVA analysis revealed a significant between-group difference in the multivariate analysis (F1.17 =24.003, p<0.001). The APDF range showed a general trend for higher values in the Case group than the Control Group, but this was not statistically significant (F1.17 =2.864, p=0.109). The differences in both median muscle activities and APDF range were most obvious between Fastest Speed and Constant Speed conditions for both groups, and Case group seemed to show a more exaggerated response than the Control Group. For wrist kinematics, there were no clear differences between groups in median radio-ulnar joint position and extent of movement range in different tasks. A general of higher angular accelerations was found in Control Group. The Case Group had significantly higher discomforts in all tasks compared to Control Group. Together these results suggest that the Case Group had different muscle activity patterns and different movement characteristics compared to the Control Group. The present results are consistent with previous research that suggested altered motor control is important in contributing to the development of musculoskeletal disorders. This study is one of the first to demonstrate such mechanisms in the control of forearm muscles and the wrist joint in computer mouse users, and these findings have important implications for understanding mechanisms underlying work-related musculoskeletal disorders.

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