Using the VDTlog Software to Evaluate Upper-extremity Musclar Fatigue of Computer Users
Date Issued
2012
Date
2012
Author(s)
Wang, Chen-Ling
Abstract
Extensive computer use is an identified risk factor for computer work-related musculoskeletal disorders. However, only limited studies used objective measurements to assess the association between computer work loadings and musculoskeletal fatigue in field study. Previous studies reported that derived electronic activity recording parameters, i.e., mouse moving speed and acceleration of the VDTlog monitoring system, were correlated with the median frequency of surface electromyogram (sEMG) measurement, and therefore could be considered as indicators for computer mouse users’ performance evaluation. The objectives of this study were: (1) to correlate the measurements with sEMG and VDTlog monitoring system, respectively, for continuous computer work in order to identify appropriate indicators for the upper-extremity musclar fatigue, and (2) to apply VDTlog monitoring system in field study to evaluate the upper extremity musculoskeletal fatigue of the computer users and explore the possible causes for the occurrence of upper extremity musculoskeletal discomforts.
In the first part of this study, there were 30 male subjects recruited who didn’t have musculoskeletal disorders in the upper extremity in the past year. All subjects were asked to play a computer game continuously for two hours in an ergonomics laboratory. sEMG was used to monitor the activities of extensor digitorum communis (EDC), flexor digitorum superficialis (FDS), and bilateral upper trapezius during the computer game playing. Meanwhile, VDTlog monitoring system was also applied to record the electronic activities of computer mouse and keyboard operation. Statistical analysis on the amplitude and median frequency of sEMG measurement and various percentiles of derived speed and acceleration parameters for mouse movement with VDTlog monitoring system were conducted to characterize their distributions and explore the correlation among them. Results showed that the median frequency of EDC(P<0.0001), the first (P<0.005) and 99th (P<0.05) percentiles of mouse-moving speed and the 99th (P<0.005), 95th (P<0.02), 90th (P<0.04), 5th (P<0.03), 1st (P<0.005) percentiles of mouse-moving acceleration were significantly different between the 1st and 2nd hours in this two-hour game experiment. Mixed model analysis on the speed and acceleration parameters derived from VDTlog monitoring and the amplitude and median frequency of sEMG measurement indicated that the 95th, 90th and 5th percentiles of mouse-moving acceleration might be able to substitute median frequency of EDC as indicators for upper-extremity muscular fatigue of the computer users.
In the second part of this study, there were 39 computer workers recruited as study subjects. Their daily activities with computer at work in five consecutive days was recorded with VDTlog monitoring system. Questionnaire administration was conducted to collect study subjects’ personal information, while individual anthropometric data and work environmental layout were also obtained on site. Results indicated that the study subjects tended to overestimate their computer use time at work (7.32±1.83 hours) as compared to that recorded by VDTlog monitoring system (3.34±1.42 hours, p<0.0001）. The recorded mouse use time (OR=4.43, 95% CI: 1.23~33.17 for more than 2 h/day, p=0.03) were positively associated with shoulder discomforts. In contrast, the computer use time, mouse use time, and keyboard use time were negatively associated with mouse-moving speed and acceleration (p<0.05), while computer idle time (電腦閒置時間) was positively associated with mouse-moving speed (p=0.01). Accordingly, mouse-moving acceleration could be considered as an alternative indicator of upper extremity muscular fatigue for computer user. In conclusion, VDTlog monitoring system provided objective and reliable parameters for quantitative evaluation of computer work loading, in terms of use time by different computer input method, i.e., mouse and keyboard, with limited interference to the computer user. Furthermore, VDTlog features a convenient and cost-saving method for upper extremity muscular fatigue evaluation with VDTlog derived parameters, i.e., mouse-moving speed and acceleration. This study demonstrated the feasibility of applying VDTlog monitoring system in work place to evaluate the muscular fatigue of computer users. In the future, it is anticipated to further apply VDTlog monitoring system in large scale study or long term epidemiological surveillance.
Subjects
computer work
muscular fatigue
sEMG
Type
thesis
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