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PubMed1999

A procedure to determine the individually comfortable position of visual displays relative to the eyes.

In an intervention phase, 38 operators used four different imposed screen positions (near versus distant, high versus low) for a full working day to experience the advantages and disadvantages. Screens at about 66 cm induced more reported strain than screens at about 98 cm. When operators later freely selected their individually most comfortable screen position, individually different changes due to the intervention were observed: some subjects changed to shorter, others to longer viewing distances, some operators adjusted the screen lower, others higher. These effects were confirmed in repeated tests. Thus, trying out different screen positions appears useful for arranging the VDU workstation to the individually most comfortable screen location relative to the eyes.

Analysis of Variance↗
PubMed1990

Specificity and variability of practice.

The specificity of learning principle proposes that motor skills are specific and only superficially resemble other similar skills or variations of the same skill. On the other hand, the variability of practice hypothesis derived from schema theory proposes that experiences with task variations are vital to the development of the memories (schemata) responsible for response production and learning. This paper contrasts these two positions in two experiments aimed at determining the influence of providing variable and/or specific acquisition experiences on the retention of a force production task. The results clearly indicated that acquisition practice with variations of the criterion task leads to better retention than practice on the criterion task alone. This finding is contrary to a strict interpretation of the specificity of learning principle and suggests that paradigms investigating schema notions should be expanded to include potential impacts of variability of practice on tasks experienced during acquisition.

Biofeedback, Psychology↗
PubMed2005

Evaluation of biopolymer-modified concrete systems for disposal of cathode ray tube glass.

Cathode ray tubes (CRTs) from computer monitors and television sets, which contain significantly high percentage of lead (Pb) by weight, represent an enormous and growing hazardous waste problem in the United States and worldwide. As a result, new technologies are needed to cope with current CRT waste stream and increased hazard and build new markets for its recycled components, developing commercially viable concrete composites, as well as minimizing CRT disposal problems. In this study, commercially available biopolymers, such as xanthan gum, guar gum, and chitosan, were used to encapsulate CRT glass waste, reducing the Pb leachability. The biopolymers utilized contain a number of useful functional groups, such as carboxyl (xanthan), hydroxyl (guar), and amino groups (chitosan), which play important roles in binding and stabilizing Pb onto concrete structures. The use of biopolymers in concrete systems can create a stable interpenetrating cross-linking composite that will last for many years. Results from these new composites show 30% higher compressive strength than standard concrete and a sharp decrease in lead leachability from several thousand milligrams per liter initially to an amount of three-tenths milligrams per liter or lower values (much lower than the U.S. Environment Protection Agency standard for hazardous waste of 5 mg/L by the toxicity characteristic leaching procedure test), and for some of the composites leachability is below even the standard for drinking water. This efficient and cost-effective CRT-biopolymer-concrete composite is a new class of biopolymer-modified material that can potentially perform a significant role in relieving the current CRT issue.

Biopolymers↗
PubMed2003

Examining RULA's postural scoring system with selected physiological and psychophysiological measures.

The Rapid Upper Limb Assessment (RULA) survey is a posture-sampling tool used specifically to examine the level of risk associated with upper limb disorders of individual workers. This paper examines the relationship between RULA's postural scoring system and measures of surface electromyography (EMG), self-reports of discomfort, and job attitude questionnaires. Twenty participants each performed a 30-min typing task on a computer in 3 working postures based on RULA's scoring system. A statistically significant difference was found only in perceived discomfort. The perceived discomfort results demonstrated that RULA was able to identify "high risk" postures. The next question we need to ask is, does perceived discomfort result in tissue damage, or does tissue damage yield discomfort?

Adult↗
PubMed2003

Prevention of deep vein thrombosis in VDU work.

This paper introduces preventive measures against Deep Vein Thrombosis (DVT) during Visual Display Units (VDU) work. Four experiments were conducted in order to address this issue. The effectiveness of the preventative measures was evaluated by measuring foot swelling. The results indicated that the following 3 methods would be particularly effective: (a) occasionally adopting a reclining posture with a footrest, (b) 10-min walking every 50-60 min of VDU work, and (3) stretching. In addition we predicted that taking a deep breath could sometimes be effective. DVT is likely to occur in daily life and its incidence can be related to the long-term postures associated with VDU work. This paper suggests that VDU workers should be aware of the risk of DVT and take preventative measures.

Computer Terminals↗
PubMed2003

Symptoms and clinical findings from the musculoskeletal system among operators at a call centre in Sweden--a 10-month follow-up study.

The musculoskeletal health among 57 operators at 1 call centre in Sweden was studied with 10 monthly follow-ups, parallel to a reference group of 1,226 professional computer users in other occupations. Operators at this call centre were more symptom-loaded than the other professional computer users in spite of their younger age and shorter exposure to computer work. Symptoms were long-lasting or recurrent. Muscle tenderness and nerve affections in the neck-shoulder region were the most common specific findings and diagnoses at medical examination of incident symptom cases. More extensive studies should be done on the working conditions and health status among call centre workers.

Adult↗
PubMed2003

Comparison between the strain indicator HRV of a head-based virtual retinal display and LC-head mounted displays for augmented reality.

Augmented Reality uses Head Mounted Displays (HMD) to overlay the real word with additional virtual information. Virtual Retinal Displays (VRD), a new display technology, no longer requires Liquid Crystal Displays (LCD). VRD technology addresses the retina directly with a single laser stream of pixels. There are no studies on the user's informational strain in this new VRD technology. Various papers have shown that Heart Rate Variability (HRV) is a valid indicator for the user's informational strain. An empirical test revealed no difference in the user's HRV between VRD technology and LCD technology. Consequently, there seems to be a comparable user informational strain regarding the display types.

Adult↗
PubMed2003

Effect of subjective and objective workload on asthenopia at VDU workplaces.

An ergophthalmological tool has been developed to investigate effects of subjective and objective workload on work-related visual complaints (asthenopia). In field studies on different visual display unit (VDU) workplaces effects of objective and subjective workload, work intensity, and work breaks (5-9 min/hour) could be found. It could be shown that during the first hours of VDU work, asthenopic complaints have the tendency to follow effective workload. With increasing working time the effect of a general and visual fatigue overlaps other reported visual complaints in the majority of cases.

Asthenopia↗
PubMed2003

A new approach to the mouse arm syndrome.

OBJECTIVES: The study validates a new computer mouse concept. The tested device is a small mouse with a pivoting pen-shaped handle. The hypothesis behind the design is the assumptions that the pen grip requires less static tension than the normal mouse grip and that fine-motor, high precision tasks normally are done with finger movements with forearm at rest. METHODS: Four muscles were monitored with electromyography (EMG) during work with a new mouse and with a traditional mouse. RESULTS: EMG activity was significant lower, in M. pronator teres--46%, M. extensor digitorum--46%, M. trapezius--69%, and M. levator scapulae--82%, during work with the new mouse as compared to the traditional mouse. CONCLUSION: Altering the design of the computer mouse can significantly reduce muscular tension.

Carpal Tunnel Syndrome↗
PubMed2003

Reducing musculoskeletal discomfort: effects of an office ergonomics workplace and training intervention.

Effects of an office ergonomics workplace and training intervention on workers' knowledge and self-reported musculoskeletal pain and discomfort were investigated. An instructional systems design process was used to develop an office ergonomics training program and the evaluation tools used to measure the effectiveness of the training program on workers' office ergonomics knowledge and skills. It was hypothesized that the training and workplace intervention would allow the worker to more effectively use their workplace through increased office ergonomics knowledge and skills. Following the intervention, there was a significant increase in workers' office ergonomics knowledge and awareness. Self-reported work-related musculoskeletal disorders significantly decreased for the group who had a workplace change and received ergonomic training relative to a workplace change-only group and a no intervention control group.

Computer Terminals↗
PubMed2003

Sitting posture, postural discomfort, and visual performance: a critical view on the interdependence of cognitive and anthropometric factors in the VDU workplace.

The study focuses on individual and standard visual display unit (VDU) workplaces with respect to performance and muscular load. Three different work settings were realized: The workplace was either adjusted to individual preferences or to the European standard. The third condition mirrored exactly the individual setting, however participants were told that it was set according to another standard. Dependent variables were visual performance in a search task, the rated muscular load, and individual preferences. Results show that both individual work settings yielded a superior performance as compared to the standard. However, performance and muscular comfort improved when participants knew they had adjusted the workplace. Apparently, VDU users follow a intuitive rationale adjusting their work setting minimizing muscular load and optimizing performance.

Adult↗
PubMed2003

Visual Costs of the Inhomogeneity of Luminance and Contrast by Viewing LCD-TFT Screens Off-Axis.

In this study the anisotropic characteristics of TFT-LCD (Thin-Film-Transistor-Liquid Crystal Display) screens were examined. Anisotropy occurs as the distribution of luminance and contrast changes over the screen surface due to different viewing angles. On the basis of detailed photometric measurements the detection performance in a visual reaction task was measured in different viewing conditions. Viewing angle (0 degrees, frontal view; 30 degrees, off-axis; 50 degrees, off-axis) as well as ambient lighting (a dark or illuminated room) were varied. Reaction times and accuracy of detection performance were recorded. Results showed TFT's anisotropy to be a crucial factor deteriorating performance. With an increasing viewing angle performance decreased. It is concluded that TFT's anisotropy is a limiting factor for overall suitability and usefulness of this new display technology.

Adult↗
PubMed2005

The effect of an ergonomic intervention on musculoskeletal, psychosocial, and visual strain of VDT data entry work: the United States part of the international study.

The United States MEPS (musculoskeletal--eyestrain--psychosocial--stress) study consisted of 1 group of 28 female data entry operators. The intervention was in 3 parts: workstation redesign (including advanced ergonomic chairs, motorized adjustable workstations, advanced adjustable keyboards, adjustable copyholders, adjustable footrests, monitor support surfaces) and ergonomic training/coaching and corrective lenses. After the intervention, statistically significant reductions in physical signs (trigger points, neck and shoulder mobility), subjective reports of intensity and frequency of musculoskeletal pain, and subjective reports of visual problems were observed. Static load during the work sample, as assessed by experts, improved after the intervention as did measured postural angles of head and trunk and subjective assessment of users of ergonomic characteristics of the workplaces. For all of these measures, improvements observed 1 month after intervention were also observed in the 1-year follow-up. Trapezius load, as assessed by electromyography (EMG), decreased after intervention, but then increased in the follow-up. The increase was interpreted as a calibration problem.

Adult↗
PubMed2005

The effect of an ergonomic intervention on musculoskeletal, psychosocial, and visual strain of VDT data entry work: the Polish part of the international study.

A group of routine data entry operators (female) was included in the Polish MEPS (musculoskeletal--eyestrain--psychosocial--stress) study. Before the intervention, ergonomic assessment revealed improper working conditions such as inadequate lighting, uncomfortable chairs, and lack of forearm and wrist support while medical examination revealed that trapezius muscle load along with upper arm, head and back angles were higher than advisable. Subjects complained about neck and shoulder pain, visual problems, and psychosocial conditions. The ergonomic intervention included installation of new luminaires and Venetian blinds, new chairs, repair of ventilators, and optometric corrections. The results after the intervention showed mainly improvement in chair comfort, lighting conditions, visual strain, and sitting posture. However, financial limitations did not allow satisfactory completion of the intervention leading to a mixed interpretation of the results.

Adult↗
PubMed2006

Baseline prevalence of symptoms related to indoor environment.

AIMS: Health problems associated with indoor environments have been reported and discussed extensively during the past few decades, not least in Sweden. There is, however, great uncertainty concerning the background prevalence of the symptoms in question. The main objective of the present study was to investigate the prevalence of general, mucosal, and skin symptoms in the Swedish population. METHODS: A survey comprising 3,000 randomly selected Swedes, age 18-64, was carried out. The survey addressed 25 symptoms, principally general, mucosal, and skin symptoms. A number of other areas were covered and individual data registered at Statistics Sweden were added. The response rate was 70% (2,154 cases). RESULTS: The prevalence of symptoms in the Swedish population was found to accord with results in studies based on different kinds of samples. Women reported significantly more single symptoms, as well as sets of symptoms, than men. There was no clear connection between age and symptoms. The prevalence of symptoms was slightly lower among employees compared with non-workers. Office workers did not report symptoms related to "sick building syndrome" (SBS) more frequently than employees not working in offices. SBS symptoms, skin symptoms, and symptoms similar to those reported by individuals with "electric hypersensitivity" were significantly more prevalent among employees with extensive VDU usage. CONCLUSIONS: The prevalence of reported health complaints accords with that which has been found in previous studies. The background prevalence reported here can serve as a reference for further studies. The high prevalence of symptoms among individuals with extensive VDU usage gives cause for further studies.

Adolescent↗
PubMed1991

The effects of flicker on eye movement control.

Groups of typists with extensive experience of screen-based editing and groups of students with no such experience carried out a reading task under three conditions of illumination (50-Hz flicker, 100-Hz flicker, and steady illumination). Subjects read a sentence, which was followed by the presentation of a single stimulus word on the same line to the right-hand side of the display. The task was to decide whether or not the stimulus was present in the sentence. Subjects were free to re-inspect the sentence when making the decision. Eye movements were measured as subjects completed the task. In comparison with students, typists adopted a more cautious reading style, making more right-to-left saccades, shorter saccades, and more corrective eye movements. Flicker affected the performance of both groups of subjects in the first pass, leading to shorter saccades. In the second pass, its effect for students was to shorten the extent of large saccades made to check the presence of the stimulus word. In the group of typists, flicker led to an increase in the variability of saccade extent and a doubling in the number of small corrective saccades. The results are consistent with the view that flicker has two distinct effects on reading, both of which are potentially disruptive. The first relates to an increase in the number of prematurely triggered saccades, which are, as a result, less accurate. The second is an increase in the number of saccades perturbed in flight, which land short of their intended target. These two mechanisms may have different consequences for readers, depending on their reading style.

Adult↗
PubMed1991

Hazard assessment of video display units.

This report describes the results of a study of potential health hazards of video display units (VDUs). The specific elements of the study included characterizing the emissions of ionizing and nonionizing radiation and exposures to electromagnetic fields. There was no evidence that operators are exposed to electric, magnetic, or ionizing radiation fields significantly above ambient levels. Significant x-ray leakage cannot occur under any credible conditions. In addition to the ergonomic aspects of VDU work, reports on the health aspects of VDU operators were investigated. The results of the study, based on the specific hazards evaluated, do not support allegations that VDU operation is hazardous beyond the identified transient discomforts associated with characteristics of the work performed. A high-profile employee education program was initiated to minimize discomforts and unwarranted concerns.

Air Pollutants, Radioactive↗
PubMed1996

Effects of key stiffness on force and the development of fatigue while typing.

An experiment was conducted to investigate the effect of key stiffness on the development of fatigue, keyboard reaction forces, and muscle electromyography (EMG) responses. Six subjects typed continuously for 2 hours on each of two keyboards (0.28 N or 0.83 N resistance keys, presented in random order). Keyboard reaction force and root mean square finger flexor and extensor EMG were recorded for 2 minutes at 250 Hz for every 10 minutes subjects typed. After typing for 2 hours subjects were given a 2-hour rest break and then typed on the remaining keyboard for an additional 2 hours Fifty-four percent more peak force, 34% more peak finger flexor EMG, and 2% more peak finger extensor EMG were exerted while using the 0.83 N keyboard. Peak and 90th percentile values showed similar trends and were well correlated for force and finger flexor and extensor EMG. Subjects typed much harder than necessary (4.1 to 7.0 times harder on the 0.28 N keyboard and 2.2 to 3.5 times harder on the 0.83 N keyboard) to activate the keys. Fatigue was observed on the 0.83 N keyboard during 2 hours of continuous typing, but the trends were mild. It appears that the ratio of typing force to flexor EMG may not be a sensitive enough indicator of fatigue for low-force high repetition work.

Adult↗