一、直接量測與觀察法於工作現場手部作業評估之比較 二、電腦監測系統於職場運作之評估

Abstract

Part I: To evaluate the risk factors for upper extremity musculoskeletal disorders, the direct measurement has the advantage of better validity while the observation method and self-report have the strength of convenience in operation. The aim of this study are to evaluate the correlation of exposure variables monitored by direct measurement and observation method, respectively, and to find out the most feasible and valid parameters by observation method to assess hand activity at workplace. A total of 35 different tasks by 19 subjects of 10 companies were included in this study, which were primarily involved in upper extremity activity. All subjects filled in a modified Nordic Musculoskeletal Questionnaire to report their health outcome prior to the beginning of this study. Then, the study subjects were asked to work as usual for the designated task for 15 minutes or more than 5 cycles per task. Meanwhile, direct measurements, including surface electromyography and biaxial electrogoniometers for wrist, were applied to record the bioelectronic signals for hand activity. All the subjects’ hand activities were videotaped and, later, rated by a reviewer according to the Strain Index (SI) checklist and hand activity level (HAL) checklist issued by the American Conference of Governmental Industrial Hygienists. Both direct measurement and observation method provided exposure variables for exertion force and frequency. Results showed that the prevalence of discomforts in wrist was higher than other upper extremity parts among the study subjects. The parameters of exertion frequency by direct measurement and video observation were significantly correlated (r=0.62, p<0.01). The efforts per minute estimated by SI checklist was correlated with the mean power frequency of exertion (r=0.66, p<0.001) and the root mean square of wrist deviation speed by the biaxial electrogoniometers (r=0.51, p<0.01). However, such consistence was not found for exposure variable of exertion force. The finding of the present study suggested that the frequency of upper extremity motion estimated by observation method could be used as a feasible indicator for exposure loading assessment at workplace if direct measurement is not feasible for all study subjects. Part II: To assess the physical loading of computer work, the electronic activity monitoring system provides an alternative tool for computer use time estimation in practice. The aims of this study were to study the reliability of an electronic activity monitoring system, VDTlog, in computer use time estimation, and its applicability as an exposure assessment tool in the field. Twenty two participants were recruited in this study with most of their daily work composed of computer-based office work. Three methods including video record observation, self-report and VDTlog were used to gather the information related to computer use. During three consecutive working hours, two cameras were turned on to record, and VDTlog was used to estimate the keyboard, mouse, and computer use time. Subjects had to complete a self-report questionnaire about aforementioned computer use times for each hour during the observation period. The estimates of keyboard, mouse and total computer use time for study hours by self-report and VDTlog were compared to video record observation by Pearson’s correlation analysis. The average time of total computer use was 63% of the video record observation period. Estimation by VDTlog was highly correlated with video record observation for total computer use time (r=0.98). The relative errors decreased along with the percentage of total computer use time in the monitored working hours among the subjects. It implied that the electronic activity monitoring system, VDTlog, seemed to be well comparable to video record observation, and it is a valid and reliable tool for the collection of time related information on the highly intensive work activities of computer workers.