Visual Display Terminal Workstation Research Articles

Ergonomic Study of VDT Workstations for Wheelchair Users

ABSTRACT This study presents a three-dimensional computer-modelling system based on Transom JACK software, with 3D objects/equipment and human subjects with specific anthropometric measurements to visualize and evaluate human-machine interaction. A computer simulation method is then adopted to evaluate some VDT (Visual Display Terminal) workstations to determine whether they are appropriate for use by wheelchair users. The study indicates that currently available commercial computer desks present difficulties, in terms of both spatial design and reachability of peripheral devices, to wheelchair users. Some VDT tasks result in awkward body postures in virtual subjects. New VDT workstations are designed and recommended to solve the shortcomings found.

Ergonomics and musculoskeletal symptoms in surgeons performing endoscopic procedures for benign prostatic hyperplasia.

Background and purpose:Benign prostatic hyperplasia (BPH) is the most common urologic disorder affecting older men, necessitating medical or surgical intervention. Limited data exists regarding the effect these surgeries have on the endourologist’s musculoskeletal system following the surgery because of the required difficult posture, prolonged procedures, repetitive movements, and the settings of an adjustable visual display terminal workstation. The aim of our study was to survey the prevalence and possible causes of musculoskeletal disorders among endourologists performing transurethral resection of the prostate (TURP) or laser prostatectomy using either holmium laser enucleation or thulium laser enucleation.Materials and methods:An email inviting all members of the Endourological Society to participate in the survey was sent. The questionnaire included different demographic and practice characteristics, with concern regarding performing either TURP or laser prostatectomy and the incidence and type of musculoskeletal incidents following these surgeries. All responses were collected by a commercially available internet based survey host (www.surveymonkey.com) over a period of 6 weeks.Results:Of the 121 complete responses, 84 (69%) of endourologists complained of a musculoskeletal disorder following TURP or laser prostatectomy. The most frequent complaint was for neck (64%), followed by back (57%), shoulder (48%), hand (40%), and elbow (18%). The average prostate volume turned out to be the most compelling predictor for musculoskeletal disorder occurrence with an average prostate volume of 76 g operated on by the complaining group compared with 59 g in the noncomplaining group. Those with more severe symptoms were linked to a mean prostate size of 80 g (60–146) and constantly complained of shoulder, neck, or back trouble compared with the less-severely complaining group.Conclusions:A high prevalence of musculoskeletal complaints among urologists performing endourologic prostatectomy was confirmed and was found to be proportionally related to the size of the prostate. The integration of an ergonomic specialist inside the operation room to watch and correct the surgeon’s position during endourologic procedures may reduce the endourologist’s exposure to these occupational hazards.

Exploring the impact of external shading system on cognitive task performance, alertness and visual comfort in a daylit workplace environment

The authors examined the effect of external shading system on cognitive performance, alertness and visual comfort of visual display terminal (VDT) users under two realistic office lighting settings in this study. Daylight was the source of illumination being considered as the most significant and preferred one. A total of 26 participants performed visual and cognitive demanding tasks as well as providing subjective alertness, performance and visual evaluations in a full-scale mock-up VDT workstation. Two trials (with and without shading system) were executed during one experimental session. Results revealed that the use of a shading system improves the performance of a user on colour-naming task requiring sustained attention, while no differential effects were observed on tasks involving other cognitive skills such as search velocity and vigilance. Within-subject performance differences were more pronounced during morning hours. Higher performance was reported in some cognitive tests when the subjective sensation of visual discomfort was lower.

A Study on the VDT Workstations Usage for Office Workers

Objective and Background: Due to increase in Musculoskeletal Disorders (MSDs) relating to computer use, a number of ergonomics recommendations have been proposed in order to tackle this problem. However, some of these recommendations have been conflicting. Method: This study was to survey the VDT (Visual Display Terminal) use of office workers. The subjects were 452 workers at 13 places of business and the data were collected by self-administered questionnaire. Results: As a result, prevalence of self-reported MSDs of all VDT workers was 90.2% and shoulder took up 57.0% and neck 38.3% by symptom part of body. The population of computer use of more than 6h/day was 84.5%, and 33.8% also reported using the VDT 2~3h/day without the rest time. Desktop computer users were 95.6%, and a 17-inch monitor accounted for 42.0% among the desktop users. As a result of satisfaction survey on overall computer work, 21.1% of the total respondents said satisfied, desk complaint was about 24.6%, and chair complaint was 33.4%. Despite the importance of computer environment, satisfaction was from fair to uncomfortable. Conclusion and Application: In conclusion, office workers are prone to the MSDs due to their work environment. Additionally, this study found that task was a significant effect for the majority of dependent variables, and therefore, the improvement of computer workstations work environment is urgent, and the improvement of desk height adjustment, chair seat size (length, width), backrest condition, location of keyboard (mouse) and arm rest is required.

Musculoskeletal symptoms of the upper extremities and the neck: a cross-sectional study on prevalence and symptom-predicting factors at visual display terminal (VDT) workstations.

BackgroundThe aim of this study was to determine the prevalence and the predictors of musculoskeletal symptoms in the upper extremities and neck at visual display terminal (VDT) workstations.MethodsIn a cross-sectional study 1,065 employees working at VDT > 1 h/d completed a standardised questionnaire. Workstation conditions were documented in a standardised checklist, and a subgroup of 82 employees underwent a physical examination.ResultsUsing the Nordic Questionnaire, the 12-month prevalence of symptoms of the neck, shoulder region, hand/wrist, or elbow/lower arm was 55%, 38%, 21%, and 15% respectively. The duration of VDT work had a significant impact on the frequency of neck symptoms in employees performing such work > 6 h/d.ConclusionWith regard to musculoskeletal symptoms of the upper extremities, preventive measures at VDT workstations should be focused on neck and shoulder symptoms (e.g. ergonomic measures, breaks to avoid sitting over long periods).

Analytic and rule-based decision support tool for VDT workstation adjustment and computer accessories arrangement.

One important factor that leads to the development of musculoskeletal disorders (MSD) and cumulative trauma disorders (CTD) among visual display terminal (VDT) users is their work posture. While operating a VDT, a user's body posture is strongly influenced by the task, VDT workstation settings, and layout of computer accessories. This paper presents an analytic and rule-based decision support tool called EQ-DeX (an ergonomics and quantitative design expert system) that is developed to provide valid and practical recommendations regarding the adjustment of a VDT workstation and the arrangement of computer accessories. The paper explains the structure and components of EQ-DeX, input data, rules, and adjustment and arrangement algorithms. From input information such as gender, age, body height, task, etc., EQ-DeX uses analytic and rule-based algorithms to estimate quantitative settings of a computer table and a chair, as well as locations of computer accessories such as monitor, document holder, keyboard, and mouse. With the input and output screens that are designed using the concept of usability, the interactions between the user and EQ-DeX are convenient. Examples are also presented to demonstrate the recommendations generated by EQ-DeX.

System to monitor task chair seating

Objective. To record chair data such as seat occupancy, back recline angle, lumbar engagement, and armrest location using an independent, unbiased real time data acquisition system. Design. The system should be inconspicuous. The users should be able to work effectively in their environment oblivious to concurrent data collection. Background. While human acquisition and measurement instruments provide an acceptable approach for collecting data on changing chair positions, they may bias data. Current data collection methods such as video playback can also be successful in collecting chair data, but are often time-consuming and expensive to set up. Methods. Four key areas were concentrated upon for monitoring: seat, lumbar, back recline, and armrest position. A position switch was mounted to each locale and linked to a microprocessor to track the changing positions of the chair in real time. Results. The chair provides time stamped data on the changes that take place to the chair. The data can be downloaded at the convenience of the user and researcher. Conclusions. The chair is complete and ready for data acquisition. It permits easy data collection on chair positions without hindering the user’s movement. Relevance This tool provides an automated, independent method for collecting data on chair positions. Information can be collected and studies conducted on seated durations, chair back motion while seated, chair lumbar usage, and common armrest location while in a visual display terminal workstation.

Evaluation of Ansi/Hfs 100-1988 Flicker Assessment Method

This work examined the method used in the American National Standard for Human Factors Engineering of Visual Display Terminal Workstations (ANSI/HFS 100–1988) to evaluate flicker from Cathode Ray Tube (CRT) displays. The standard specifies that “the display must be found to be flicker free for at least 90 percent of a sample of the user population under conditions representative of actual use.” However, the associated flicker compliance test is questioned as not representing realistic office viewing conditions. A psychophysical experiment was conducted to compare the detection of CRT flicker, in terms of Critical Flicker Frequencies (CFFs), under the ANSI/HFS 100–1988 viewing conditions (i.e., 0 and 20 degrees viewing angle, dark ambient, and hyphen-filled, bright-on-dark character screen) with several others, defined by combinations of ambient illuminance, display luminance, display viewing angle, and screen pattern. As expected, the results indicate that these four factors significantly affect CFFs. More importantly, the CFFs obtained under these viewing conditions were higher than those obtained under the ANSI/HFS 100–1988 viewing condition. The findings of this work indicate that the ANSI/HFS 100–1988 flicker assessment method is too conservative and may not be sufficient to ensure flicker-free viewing of CRT displays under typical office viewing conditions.

Body height-workstation settings matrix: A practical tool for ergonomic VDT workstation adjustment

This paper discusses the development of a body height-workstation settings (BH-WS) matrix for a quick and convenient ergonomic visual display terminal (VDT) workstation adjustment. The matrix is intended to be a practical tool to help VDT users adjust their workstations in order to obtain a proper seated posture. The BH-WS matrix uses two parameters, the user's body height and sex, to estimate recommended workstation settings (in numerals) based on ergonomics principles. Three estimation processes have been used. Firstly, relevant body member measurements are estimated from the body height. Then, both x- and y-coordinates of key body reference points are calculated. Finally, the coordinates of the VDT workstation's reference points are determined to match with those of the body reference points. The recommended settings are then derived from these reference points.

Analysis of ocular surface area for comfortable VDT workstation layout

This paper proposes a comfortable visual display terminal (VDT) workstation layout based on an analysis of ocular surface area (OSA). A large OSA induces eye irritation and eye fatigue because the eye surface is highly sensitive to various stimuli. The authors considered that OSA must be one of the useful indices of visual ergonomics and applied it to evaluate VDT workstation layout. Each subject was asked to perform a word processing task using four different VDT workstation layouts. It was found that the main factor affecting OSA was not cathode ray tube (CRT) height itself but the distance between the CRT and keyboard. Thus the following workstation layout is recommended to realize comfortable VDT operation: (1) the desk height should be adjusted to the user's height; and (2) the CRT display should be set closer to the keyboard to provide a smaller OSA.

A Comparison of VDT Workstation Adjustment Methods by Evaluating and Optimizing VDT Operator's Seated Posture.

Three methods of visual display terminal (VDT) workstation adjustment were compared in this study in order to investigate their effects on the operator's seated posture. The first two methods were adjustments made both with and without any suggestion on the correct seated posture. The third method was an adjustment after which the workstation settings were initially set according to the results recommended by the IntelAd computer program. Ten male and 5 female participants were asked to readjust a VDT workstation until their most comfortable seated posture was obtained. When comparing the final seated postures to the ones ergonomically recommended, it was found that the workstation adjustment assisted by the computer program yielded the best result, followed by the adjustment without any suggestion on the seated posture, and then the adjustment with a suggestion on the seated posture. Furthermore, factors such as gender and typing skill level were not found to have any significant influence on the results.

Commentary

Using a visual display terminal (VDT) is today a common occupational task with both benefits and hazards. One of the hazards is the occurrence of musculoskeletal disorders. This paper examines the possible causes of such disorders and suggests some preventive strategies. The debate on the relationship between musculoskeletal disorders and VDT usage usually centers around occupational factors (eg, constrained posture, poor ergonomic design of the workplace, equipment design), work-related psychological factors (eg, perceived high job demands, mundane, boring and repetitive job activity, little control, poor support from colleagues and superiors), and psychosocial factors (eg, biodemographic characteristics such as age, previous musculoskeletal injuries, emotional stress, family burden, environmental factors). Improving the ergonomic design of VDT workstations, changing occupational legislation, and improving occupational health services have been suggested as means to decrease the incidence of musculoskeletal disorders among VDT workers. Much research with a multidisciplinary approach is still needed.

Effectiveness of the C-Sharp: reducing ergonomics problems at VDTs

The use of visual display terminals (VDTs) has been associated with complaints of visual fatigue and body discomfort. In an effort to eliminate some of these problems, an ergonomic emphasis has been placed on the design of computer workstations. A new device, the C-Sharp, has been developed to help reduce some of the ergonomics problems related to long-term VDT usage. The C-Sharp was designed to alleviate visual strain and temporary myopia by reducing the amount of muscular work associated with accommodation and convergence to near targets. It was also designed to eliminate glare. The present study is an ergonomics evaluation to determine whether the C-Sharp meets accepted standards and guidelines. Specifically, the objectives of the research are to determine the effects of the C-Sharp on operator reading and search performance, perceived comfort, body posture, and visual acuity. The C-Sharp is compared with mesh-glare filter and no-glare filter device conditions. Subjects were blocked into three groups based on age and type of vision correction (with or without bifocals). Results indicate that the C-Sharp meets the recommendations of the Americal National Standard for human factors engineering of visual display terminal workstations. No differences in objective performance were found between the three glare device conditions. The C-Sharp allowed bifocal wearers to keep their necks in natural postures rather than tilted backwards. Post-session far visual acuity worsened regardless of the device condition.

Canvass committee members sought for ANSI/HFS 100 revision

The first revision of the Human Factors and Ergonomics Society's American National Standard for Human Factors Engineering of Visual Display Terminal Workstations (ANSI/HFS 100-1988) is expected to be available for public review and comment in fall 1993. According to ANSI policy, all persons who are materially and directly affected by the standard may comment on the revised document, which must receive majority approval by the canvass committee before it is accepted as a U.S. national standard. The topics covered by the standard include: keyboard and non-keyboard input devices, CRT and flat-panel output devices, the ambient environment of office computer workstations, and office furniture used with computers.

Visual comfort in VDT operation: physiological resting states of the eye.

To recommend a comfortable visual display terminal (VDT) workstation design in an aspect of visual ergonomics, physiological resting states of the eye in 3 visual systems, pupil, vergence, and accommodation, were objectively investigated in 3 experiments. Experiment 1 ascertained a positive display polarity (dark characters on a bright background) and an illumination level of 500 lx to be the most appropriate working conditions, by using pupil analysis and subjective visual comfort in 10 subjects. Dark vergence, in experiment 2, was evaluated to be at a distance of about 50 cm from the eye, as an average in 14 subjects. Dark vergence was found to shift farther with an upward gaze while a nearer shift occurred with a downward gaze. In experiment 3, the average dark focus for 11 subjects was found to be 1.4 diopters (D) or a distance of about 74 cm from the eye. The positive correlation between refractive status of the eye and dark focus was statistically significant (r = 0.602). The ergonomic recommendations for a VDT workstation obtained in this study are a positive display polarity with an appropriate lighting condition, a downward gaze, and a viewing distance between 50 and 70 cm. These recommendations are considered to reduce visual fatigue due to prolonged VDT work and to facilitate visual comfort at work.

Effectiveness of the C-Sharp for Reducing Ergonomic Problems at VDT Workstations

The C-Sharp was designed to help reduce some of the ergonomic problems associated with long-term use of visual display terminal (VDT) workstations. The C-Sharp projects the viewed image at a farther distance than typical VDTs to reduce the amount of muscular work involved in accommodation and convergence to near targets. This may help to reduce or eliminate visual strain and temporary myopia. It was also designed to eliminate glare. The present study was conducted to evaluate the C-Sharp from a human factors standpoint and to assess its ability to reduce problems related to VDT use. Results indicate that the C-Sharp meets many of the recommendations of the American National Standard for Human Factors Engineering of Visual Display Terminal Workstations. The C-Sharp also allows bifocal wearers to keep their necks in natural postures rather than tilted backwards. In general, the C-Sharp has potential to reduce problems associated with VDT use.

American National Standard for human factors engineering of visual display terminal workstations : Human Factors Society The Society, Santa Monica, California, USA, ANSI/ HFS Standard No 100-1988, 1988, 90 pp

American National Standard for human factors engineering of visual display terminal workstations : Human Factors Society The Society, Santa Monica, California, USA, ANSI/ HFS Standard No 100-1988, 1988, 90 pp

American National Standard for Human Factors Engineering of Visual Display Terminal Workstations: A Report to the Society

The American National Standard for Human Factors Engineering of Visual Display Terminal Workstations, the first standard sponsored by the Human Factors Society, is in the final stages of acceptance as an American National Standard. This standard addresses the physical and perceptual aspects of the visual display terminal workstation as used in text processing, data entry, and data inquiry. Standards take on many different forms and fill a variety of needs. Basically a standard provides a reference. Some standards are written so that two systems may be designed to complement each other or fit together. Lightbulbs and fixtures designed to the same standard will work together. In the case of human factors standards one half of the system is already designed, the human. The variety of the design of this part of the system requires that human factors standards identify the parameters to be considered and the corresponding measurement methods needed to insure that the equipment is designed to fit the individual human. A good solution needs to be based on the particular set of circumstances at hand. The voluntary standards method, known as the American National Standards, provides a vehicle for specifying the appropriate parameters and measurement methods while incorporating the necessary flexibility required to insure good designs for individuals. The purpose of this panel session is to provide the society with an interactive session with representatives of the standards drafting committee. A brief history of the committee and its activities will be presented. The panelists will then describe the approach taken in each of the major sections, the mandatory requirements, and the elements the panelists consider to be of particular interest

Guide to the draft American national standard for human factors engineering of visual display terminal workstations

Guide to the draft American national standard for human factors engineering of visual display terminal workstations