VDT阅读作业脑力负荷的评价

目的探讨采用主观评分法、主任务评定法、心理生理学评定法3种脑力负荷评定方法评价视频显示终端(visual display terminal,VDT)阅读作业脑力负荷的可行性。方法14名大学生(为志愿受试者)在计算机上阅读短文各自15,30,60 min,分别为A,B,C组,测定分析受试者完成3组阅读时的库柏-哈柏(Cooper-Harper Scale)量表评分、正确率、阅读速度、阅读效率、心率变异性、瞳孔直径变化率、眨眼率等脑力负荷评定指标。结果随着阅读时间的延长,库柏-哈柏量表评分分值、正确率、阅读速度,瞳孔直径,眨眼率的差异无显著性;C组与A组相比,阅读效率下降;阅读与休息时相比,眨眼率减少;心率变异性(heart rate variability,HRV)总的频域值(TP)、极低频成分(VLF)、低频成分(LF)、高频成分(HF)、平均正常RR间期的标准差(SDNN)值升高,但3组之间比较,差异无显著性。结论60 min阅读作业在生理和主观评估对机体有一定的影响。主观评分法、主任务评定法、心理生理学评定法3种脑力负荷评定方法的结论基本一致,能在一定程度上反映阅读任务的脑力负荷信息,可作为脑力负荷评价某个方面的指标。     

Survey on visual and musculoskeletal symptoms in VDT workers]

With the spread of visual display terminals (VDT) in offices, the numbers of workers using VDT and the working hours at such equipment have increased rapidly in recent years. Also, preventive measures for fatigue have been proposed and the office-working environment has been improved. To examine the effects of the rapid changes in working conditions and environment on the health of VDT workers, we conducted a questionnaire survey in 2002. A self-reported questionnaire was distributed to 3,927 office workers; 2,374 (60.5%) responded. Subjects whose questionnaires had missing data were excluded from analysis. As a result, 1,406 (male: 1,069, female: 337) workers aged 20 to 59 were subjected to analysis. By a logistic regression model, we examined the association between VDT use and visual and musculoskeletal symptoms. Prevalence of eye strain and/or pain (72.1%) was the highest, followed by neck stiffness and/or pain (59.3%), low back stiffness and/or pain (30.0%) and hand or arm strain and/or pain (13.9%). Women consistently reported more discomfort than men. As a result of the logistic regression model, eye strain and/or pain was associated with dissatisfaction with airflow, but not with factors affecting visual symptoms as reported in previous studies, for example, reflection of light and blurred characters on the screen. It was thought that airflow appeared as a risk factor because the lighting environment had been improved in offices to prevent reflection of light on the screen. Neck stiffness and/or pain was associated with raising the shoulders during VDT work, the unsuitable shape of the computer mouse for a hand, and the inconvenient arrangement of the mouse in relation to the body. Hand or arm strain and/or pain were associated with the arrangement of the mouse and inappropriate height of the desk. Low back stiffness and/or pain were associated with dissatisfaction with the chair and using the keyboard without a wrist rest. Although measures to prevent fatigue had been implemented for VDT workers, risk factors for musculoskeletal symptoms would be the same as in previous studies.     

Association between duration of daily VDT use and subjective symptoms

BACKGROUND: Although visual display terminal (VDT) work has become a common task among office workers, surveys which would help to determine the allowable duration of daily VDT use are limited. METHODS: We investigated more than 25,000 workers three times over a 3-year period using a self-administered questionnaire. Three factors, namely mental, physical and sleep-related symptoms, were extracted by factor analysis. Adjusted means of each factor score were compared with the duration of daily VDT use by general linear model. RESULTS: Physical symptoms score became higher with increasing duration of daily VDT use without a threshold effect. Mental and sleep-related symptom scores of the workers using VDT for more 5 hr/day were significantly higher than that of the groups using VDT for >1, 1-3, and 3-5 hr/day. CONCLUSIONS: Duration of daily VDT use was linearly related to the physical symptom score, and was non-linearly related to mental and sleep-related symptom score with a threshold effect of 5 hr/day.     

An experimental study on the duration of a single spell of work on VDT (visual display terminal) performance

The relation between work load and the duration of a single spell of work on VDT performance studied in an experimental word processing task. Nine healthy male college students performed 2-hour visual tasks under the following three sets of work conditions. In the first set, subjects performed VDT work for two hours without intermission. In the second set, subjects had a 10-minute intermission after a 1-hour task. In the third set, there was a 5-minute intermission after a 30-minute task. Critical flicker fusion, near point distance, subjective fatigue symptoms, heart rate, respiratory rate, blinking counts, electromyogram in upper limb and performance score were measured. Results are as follows. Decrease in critical flicker fusion, increase in near point distance and subjective fatigue symptoms appeared in all three sets of experimental conditions after two hour tasks. Increased slow wave components on electromyogram and increased errors in performance appeared after 60-minute or more tasks without intermission. Effects on the critical flicker fusion, near point distance, subjective fatigue symptoms, electromyogram, blinking counts and errors in performance were least in the third set. The results of this study suggest that in order to reduce operators' fatigue on VDT work of the conversation type, countermeasures such as shortening the duration of a single spell of work to less than 60 minutes and taking frequent short intermission are necessary.     

Central nervous system effects and visual fatigue in VDT workers

Summary To assess central nervous system effects and visual fatigue induced by work with visual display terminals (VDT), symptom frequency was assessed and visual evoked potential (VEP), critical flicker fusion (CFF) and near-point distance were measured in 24 female keypunchers before and after 2.5 h of VDT work and in 6 non-VDT-exposed subjects at the same intervals. Each keypuncher had been engaged in data entry for 1–7 (mean, 4) years. After VDT work, the number of complaints of subjective fatigue as well as an objective measure of near-point distance were significantly increased as compared with those before work; also, the N75, P100 and N145 latencies of VEP were significantly prolonged. The change of P100 latency during VDT work was inversely correlated with the number of years worked in data entry. No significant change was seen in any of these tests in the non-VDT-exposed subjects. The changes in N75 latency and subjective fatigue related to drowsiness and dullness in the keypunchers were significantly larger than those in the non-VDT-exposed subjects. The CFF was significantly lower in keypunchers than in non-VDT-exposed subjects in both the first and the second tests. These data suggest that VDT work is associated with impairment of the visual nervous system function, that VEP latencies appear to be a sensitive indicator of visual fatigue, at least transiently, and that CFF appears to be a good parameter for estimations of chronic visual fatigue.     

Survey on occupational health management of VDT workers among 84 Japanese companies.

This survey of 84 companies described the present status of occupational health management of VDT workers in Japan, in relation to the official Guideline (Guidelines on Occupational Health for VDT Work, 1985). The majority admitted 80% or more of their workers engage in VDT works. Four hours of VDT work per day was widely used as a criteria for the eligibility to the VDT health examination. Some specific measurement was performed at health examination among 54.8% of the companies. The most popular item was "near vision." A larger number of follow-up measures was performed with ophthalmic cases than with muscloskeletal cases. From these findings, with consideration to the results of the preceding literatures, we made 8 suggestions for the on-going revision of the Guideline: 1) including recommendation for flat panel display and portable computers, 2) widening target of VDT health education also to general workers, 3) clarification of the categorization of VDT workers, 4) offering practical measures to secure off VDT period, 5) use of subjective symptoms to screen high-risk workers, 6) supply of the latest scientific information on each measuring item, 7) periodical revision to provide state-of-the-art management, and 8) clear statement of the purpose and limitation of the Guideline.     

An experimental study of work load on VDT performance. Part 2. Effects of difference in input devices

Effects of the difference in input device on work load of VDT task were studied. The subjects of the experiment were eight healthy male college students (age: 21-22 yr) having a binocular vision of not less than 0.7 and no astigmatism or hyperopia. The test consisted of an experimental word processing task in which the subjects visually searched e's in given sequences of alphabetical letters displayed on the CRT and converted them to 5's through input device operation. As for experimental conditions, two kinds of input devices, namely, keyboard and lightpen were adopted and 1 h was provided as each operation time. Critical flicker fusion (CFF), near point distance, accommodation time, subjective fatigue symptoms, blinking counts, pupillary reflex, electromyogram in upper limb, neck and shoulder and performance score were measured. The results were as follows. Decrease in C.F.F. was observed in two experimental conditions during the process of operating time. Increments in complaints of subjective fatigue related to visual function were seen in the two experimental conditions after 1 h VDT task. A higher error rate in performance was observed in the subjects using the lightpen compared to the one using the keyboard. The frequency of both blinking and pupil-size changes were lower in the subjects using the lightpen compared to those using the keyboard. This suggests that the gaze time of the VDT screen with lightpen-condition is longer than that in keyboard-condition.(ABSTRACT TRUNCATED AT 250 WORDS)     

An inquiry into the factors affecting the complaints of subjective symptoms in VDT operators

In a study of VDT workers the relationship between 1) their general life condition and working environment and 2) their eye, shoulder, neck, arm, waist and back complaints and their psychological symptoms was investigated. The subjects of the study were (147 workers whose age ranged from 18 to 39 years, and who had used VDT for a monthly average of more than 40 h. The results were as follows: 1) For most of the symptoms, a tendency was observed for females to complain more than males and for younger workers to complain more than the older workers. Neck, shoulder, arm, waist and back complaints were more common than psychological symptoms. These physical complaints appeared to be the most common among VDT workers. 2) The occurrence of eye-related symptoms is related to items directly affecting sight. This reaffirms the importance of illumination for the visual system. 3) This investigation showed that a relatively good VDT working environment was secured for the subjects of the present study. It is important that consideration be given to labor management such as provision of rest period and supervision.     

VDT worker's posture and workload in free-address office system]

A free-address system is a new office layout in which a worker can freely sit in their favorite place with a computer and materials. Since this layout has recently been introduced in offices, we conducted a questionnaire survey which aimed to clarify the effects of the free-address system on visual display terminals (VDT) workers' posture and workload. A total of 203 male VDT workers who were system engineers aged 20 to 59 using a notebook computer were evaluated, of whom 150 used the free-address layout, and 53 used the fixed-address layout. The free-address layout was effective in the improvement of individual work space compared with the fixed-address layout. Also, in this layout the worker did not feel dissatisfaction with communication or support between workers. However, workers using the free-address layout assumed an unsuitable work posture, without adjusting the height of their chairs. Furthermore, this layout might have risk factors which increase neck/shoulder and low back stiffness and/or pain. Therefore, the free-address layout may have incipient problems, and it will be necessary to examine further the effects of this layout on VDT worker's health.     

Effects of VDT workstation lighting conditions on operator visual workload

Industrial lighting covers a wide range of different characteristics of working interiors and work tasks. This study investigated the effects of illumination on visual workload in visual display terminal (VDT) workstation. Ten college students (5 males and 5 females) were recruited as participants to perform VDT signal detection tasks. A randomized block design was utilized with four light colors (red, blue, green and white), two ambient illumination levels (20 lux and 340 lux), with the subject as the block. The dependent variables were the change of critical fusion frequency (CFF), visual acuity, reaction time of targets detection, error rates, and rating scores in a subjective questionnaire. The study results showed that both visual acuity and the subjective visual fatigue were significantly affected by the color of light. The illumination had significant effect on CFF threshold change and reaction time. Subjects prefer to perform VDT task under blue and white lights than green and red. Based on these findings, the study discusses and suggests ways of color lighting and ambient illumination to promote operators' visual performance and prevent visual fatigue effectively.     

Influence of work duration or physical symptoms on mental health among Japanese visual display terminal users

The present study examined the relationship of work duration or physical symptoms to the mental health of visual display terminal (VDT) workers in Japan. The mental health status of 2,327 VDT users at an administrative office was investigated using the 12-item General Health Questionnaire (GHQ-12). Subjects were asked about their age, sex, hours of daily VDT use, rest and breaks during VDT work, eyestrain, and musculoskeletal pain. Logistic regression analysis was used to evaluate the associations with mental health status (GHQ-12 scores). The mean age of subjects was 39.5 yr (SD=10.3). Among all subjects, 36.7% could rest during VDT work and 66.9% received breaks during VDT work. The proportion of subjects who reported eyestrain and musculoskeletal pain were 19.6% and 25.7%, respectively. Eighteen percent of subjects were classified into a GHQ-12 high score group. Logistic regression analysis showed that age less than 40 yr, not receiving breaks during VDT work, and the presence of eyestrain and musculoskeletal pain were significantly associated with poor mental health status (high GHQ-12 scores). Using a VDT for more than 5 h/d and being female were also marginally associated with high GHQ scores (p<0.1). In conclusion, the management of physical health as well as work duration is important for good mental health status among VDT users.     

视屏显示终端视觉疲劳对脉搏信号的影响

目的通过对脉搏信号特征的提取与分析,寻找诊断与评测VDT视觉疲劳状态的客观指标。方法由问卷调查表选定37例健康被试者,设计视觉疲劳实验。在VDT实验前后,分别采集被试者光电脉搏信号,并对被试者进行疲劳症状问卷调查和闪光融合频率计测定以及体温测量。对脉搏信号进行时域和频域分析,提取波形高度和功率谱峰值作为特征参量。结果通过对疲劳症状问卷的统计分析发现,以Rechichi提出的判断标准,视疲劳实验后,被试者均处于视疲劳状态。闪光融合频率值下降显著(P<0.05),同时体温下降显著(P<0.01)。视疲劳后脉搏信号的波形高度和功率谱峰值均显著降低(P<0.001)。结论脉搏信号的波形高度和功率谱峰值能够较客观地反映人体VDT视疲劳状态,有望作为视疲劳状态诊断与评测的客观指标。     

VDT作业人员肌肉骨骼疾病的工效学调查

目的了解VDT作业人员肌肉骨骼疾病的现状及病因,为VDT作业管理提供改善依据。方法采用问卷调查的方法,选取267名VDT作业人群为调查对象,然后对问卷进行数据统计,应用模糊综合评价方法对骨骼肌疲劳进行评价。结果受调查的VDT作业者总体上处于一种比较疲劳的状态,且有67%的VDT作业者处于有疲劳状态。VDT作业者的肌肉骨骼损伤与VDT作业空间、日连续作业时间,作业量等有关。结论 VDT作业导致的肌肉骨骼疲劳存在工效学问题,相关VDT作业空间设计者应根据相关人因工程学知识设计作业空间,相关VDT作业者应关注自己的作业管理,以保障VDT作业者的身心健康。     

Factors affecting subjective symptoms of VDT workers

In 1983, 285 (male: 129, female: 156) VDT workers and 60 (male: 30, female: 30) control subjects were examined in order to detect the factors affecting the subjective symptoms of VDT workers. Biological information (for example: sex, age), life histories, information about VDT work, tests (for example: visual acuity), symptoms and interferences to daily life of VDT workers and control subjects were collected. The following results were obtained. Female VDT workers experienced more fatigue from commuting to work, stiffness in shoulders, distant blurred vision complaints of visual acuity and sum of the scores of ocular complaints than female control subjects. Only among female VDT workers, the longer the daily working hours, the greater were their ocular symptoms. A remarkable relationships were observed between psychological burden factors (for example: self-control of VDT work, sensation of excessive VDT work) and subjective symptoms of the VDT workers (both sexes). In particular, VDT workers who considered VDT work to be excessive had marked by greater subjective symptoms than those who did not.     

Subclinical impairment in the median nerve across the carpal tunnel among female VDT operators

Sensory nerve conduction velocities in the palm-to-finger (SCV-pf), wrist-to-finger (SCV-wf), wrist-to-palm (SCV-wp), and wrist-to-elbow (SCV-we) segments and the distribution of nerve conduction velocities in the right median nerve were determined among 27 female operators aged 19–37 and 19 healthy women (controls) aged 19-31 to estimate the prevalence of subclinical carpal tunnel syndrome (CTS). Also, the WF/PF ratio, dividing the SCV-wf by the SCV-pf, was calculated to assess abnormalities of nerve conduction within the carpal tunnel. The operators were engaged in data entry in front of a visual display terminal (VDT) for about 6 h/day, and their working duration was between 1 and 17 (mean 6) years. The SCV-wf, SCV-wp, and WF/PF ratio in the operators were significantly lower than those in the controls. The rate of persons with the WF/PF ratio of less than 90%, i.e., below normal limits in the 19 controls, was significantly higher in the operator group (37%) than in the control group (0%). The operators complained of more symptoms related to CTS than did the controls, but any symptoms were not associated with slowing of nerve conduction velocities in the operators. In the controls, the WF/PF ratio was not closely correlated with skin temperature or age despite the presence of significant relations between skin temperature and the SCV-wf, SCV-pf, and SCV-wp; the interpersonal variability of the WF/PF ratio was much smaller than that of all SCVs. In the light of the present and previous studies, the rate of VDT operators with subclinical CTS seems to be high, independent of its symptoms. Also, the WF/PF ratio will be a useful and reliable screening method for the early detection of CTS due to repetitive wrist and finger movements involved in work.     

Computerized exercise program does not affect stress levels of asymptomatic VDT users

The purpose of this study was to determine whether a computerized exercise program could reduce stress levels in office workers who use video display terminals (VDTs). Fifty workers were randomly assigned to either an exercise or a control group. Twenty-four subjects were instructed to exercise twice a day for 15 minutes per session for a period of 8 weeks; the remaining 26 subjects in the control group were given no exercise program. Four dimensions of stress were measured before and after the exercise period using the Personal Strain Questionnaire (PSQ), a self-reported measure of physical and psychological stress. A multivariate T-test (Hotelling’s T ² ) was used to compare changes in stress levels between the two groups of workers, but no significant differences were found. Further analysis of the exercise group revealed that difference in compliance rates among workers did not significantly influence changes in stress levels. These results indicate that this type of exercise program does not reduce stress in asymptomatic VDT users.     

Carpal tunnel syndrome in male visual display terminal (VDT) workers

BACKGROUND: The association between working at a video display terminal (VDT) and development of carpal tunnel syndrome (CTS) is not well-established. The study surveyed the prevalence of CTS symptoms, explored the risk factors and evaluated the clinical application of hand diagrams, physical tests and electrodiagnosis among male VDT workers. METHODS: A cross-sectional study was performed in an information and communication technology company. Three-forty questionnaires were completed and 82 volunteers participated in the physical examination and nerve conduction study. The personal and occupational risk factors for CTS were analyzed. RESULTS: The prevalence of CTS symptoms was 3.8% among 340 subjects, while prolonged median motor distal latency (>4.2 msec) was disclosed in 3.7% of a subgroup receiving examination. Classic/probable CTS symptoms was associated with high body mass index (>28 kg/m(2), odds ratio = 4.1, P = 0.029) and moderate job seniority (3-5 years, odds ratio = 4.6, P = 0.023). Prolonged median motor distal latency was associated with older age (>35 years old). We did not observe correlation between CTS symptoms, abnormal NCS, positive Tinel's sign or Phalen's test. CONCLUSION: The prevalence of CTS symptoms was not high among the group of male VDT workers studied. Job seniority, but not specific tasks, was associated with CTS symptoms. More reliable and valid methods to quantify the ergonomic exposure are needed to establish the association of VDT tasks and CTS.     

我国VDT作业桌椅尺寸建设标准的探讨

通过对108名大学生志愿者进行人体测量，对30套VDT设施尺寸方面的现场调查并参考国外有关标准提出了我国VDT作业桌椅尺寸土的建议标准．目前VDT作业场所的突出问题在于腿活动范围过于狭窄，椅子对95％的女性和5％的男性显得太高，桌子面积太小．文章还讨论了标准制定的依据和参考值以及人体测量方面的问题．     

视屏显示终端操作者姿势工效学调查

对143名VDT操作者进行初态姿势观察,择其中40名进行跟班动态观察一工作日,发现姿势类型主要有六种,且以第一种为多,姿势变抉间隔时间以第四种为长。提示VDT操作者姿势和有关工效学数据不尽理想,这可能由于桌椅不配套。使用固定式桌子,建议使用可调式桌椅。     

Survey on subjective symptoms in VDT workers: complaint rate and years of service

A questionnaire survey was conducted on 271 workers of microelectronics company. The questionnaire included such items as age, years of service, working conditions and subjective symptoms related to visual, musculoskeletal and general status. The following results were obtained: Of these workers, approximately 80% operated visual display terminals (VDT). The years of service for most were less than 4 to 5 years with the average being about 2 years (Fig. 1). The working hours per day on the VDT for most of them was less than 90 min, although some workers operated VDT for 3 or more hours per day (Fig. 2). A high incidence of complaints of visual function, i.e. eye strain and blurring of distant objects, was observed. Some also complained of musculoskeletal and general symptoms (Table 1). The rates of these subjective symptoms increased with years of service (Figs. 4 and 5), while the complaint rates decreased with age (Fig. 3). Significant positive correlations were found between most of these complaint rates and length of service (Table 2), although correlations between the complaint rates and age were generally non-significant but negative. The complaints tended to increase with working hours per day, although the operators who worked for longer period per day did not seem to complain as much as those who did not work so long (Fig. 6). In conclusion, the results of this questionnaire suggest that the effects of visual display terminals (VDT) work accumulate gradually over months and years.