Knut Inge Fostervold

Postural load during VDU work: a comparison between various work postures

The aim of this study was to compare the postural load during VDU work in the following work postures: (1) Supporting and not supporting the forearms on the table top, (2) Sitting and standing positions, and (3) Sightline to the centre of the screen at an angle of 15 degrees and 30 degrees below the horizontal. The muscle load from the upper part of musculus trapezius and from the lumbar part of musculus erector spinae (L3 level) was measured by electromyography (EMG). Postural angles of head, upper arm and back were measured by inclinometers. The load on m. trapezius when using the keyboard was significantly less in sitting with supported forearms compared to sitting and standing without forearm support. Further, the time and number of periods when the trapezius load was below 1% MVC was significantly greater with support versus no support. The load on the right erector spinae lumbalis was also significantly less and the time when the load was below 1% MVC was significantly longer in a sitting work position with support versus standing without support. In addition, when using a mouse supporting the forearms reduced the static trapezius load in sitting. The results from this study document clearly the importance of giving the operator the possibility of supporting the forearms on the table top.

VDU work with downward gaze: the emperor's new clothes or scientifically sound?

Abstract Lower monitor placements, with gaze angles to the centre of the screen 30–45° below the horizontal line are proposed as an alternative to higher monitor placements advocated by prevailing guidelines. A scientific basis for this proposition has been established within a comprehensive theoretical framework, founded on an ecological systemic approach to vision. A review of the literature shows reduced visual strain and a strong tendency towards reduced symptomatology in subjects working with downward gaze. Increased musculoskeletal load is not evident in m. trapezius, while a clinically insignificant increase might be present in some other neck and shoulder muscles. Research studying subjective preferences is inconclusive at present. The evidence indicates that lower monitor placements result in less strain on the total network of muscles involved in visual display unit (VDU) work. Relevance for industry VDUs are widely used in industry. Monitor placement is a critical factor in the discussion about negative health effects associated with VDUs. A review of the present knowledge represents a basis for the development of future guidelines.

Proportions of direct and indirect indoor lighting — The effect on health, well-being and cognitive performance of office workers

Indirect lighting has been recommended as a way to accommodate lighting needs in offices. To investigate this recommendation, the effect of four ceiling-mounted lighting schemes providing inverse proportions of direct and indirect lighting were studied in ordinary office environments. The study used a 4×3 mixed randomised-repeated design. Dependent variables assessed subjective symptoms, subjective well-being and cognitive performance. Glare, a major contributor to visual strain was physically removed. Photometric measurements showed that proportions of direct and indirect lighting affect the luminous environment. Except for an association between reduced job stress severity and direct lighting, the results indicate that proportions of indirect and direct lighting do not affect the dependent variables. A main effect of the new lighting installation was revealed for subjective symptoms and cognitive performance.

VDU-screen filters: remedy or the ubiquitous Hawthorne effect?

Abstract The claim that visual display units (VDU)-screen filters improve health by reducing exposure to electrical fields and/or improving screen legibility was investigated by introducing VDU screen filters into an office environment. The study design was quasi-experimental, with the first part conducted according to a simulated control group design with one intervention and one control group. In the second part, which served as a partly switched replication, the control group also received screen filters. The first group continued their use. The dependent measures were sick leave, productivity. subjective symptoms, and musculoskeletal condition. Subjectively reported symptom improvement was found in the group that received screen filters during the initial part of the study, but that was followed by an aggravation of symptoms during the second part for the same group. No effect was observed in the control group in either part of the study. The discontinuity observed between the study parts indicates that factors other than VDU-screen filter use were responsible for the results. However, the results appear to be explained by subject reactivity, i.e. the Hawthorne effect. The results caution against premature conclusions drawn from short-term interventions and emphasise the need for a better understanding of the various psychological and task-related factors that influence subjects. Relevance to industry Visual display units (VDU) are widely used in industry. Knowledge of potential VDU-related health hazards can improve workers health and performance.

Knobology in use: an experimental evaluation of ergonomics recommendations

The scientific basis for ergonomics recommendations for controls has usually not been related to active goal-directed use. The present experiment tests how different knob sizes and torques affect operator performance. The task employed is to control a pointer by the use of a control knob, and is as such an experimentally defined goal-directed task relevant to machine systems in general. Duration of use, error associated with use (overshooting of the goal area) and movement reproduction were used as performance measures. Significant differences between knob sizes were found for movement reproduction. High torques led to less overshooting as opposed to low torques. The results from duration of use showed a tendency that the differences between knob sizes were reduced from the first iteration to the second iteration. The present results indicate that the ergonomically recommended ranges of knob sizes might differently affect operator performance.

Accommodation/vergence/fixation disparity and synergism of head, neck and shoulders

The integration of scanning eye movements with head and body movements as well as the synergetic interaction of accommodation and convergence have been known for a long time. Surprisingly, little interest, if any, has been devoted to the possible interaction between vergence/accommodation and other body muscles. Experimental evidence suggesting the existence of an eye-head-body focusing programme for maintenance of clear and single vision was published by Lie and Watten in 1987. In the present paper, these results are summarised and the two-step vergence model of Schor (1980) is extended to account for an ocular motor/body muscle interaction. New evidence of the existence of very large fixation disparities suggesting a dynamic interplay between motor and sensory compensation of angular misalignment is presented. Binocular eye movement registrations are performed while prism induced vergence capacity is measured. In extreme cases prism induced angular deviations up to 15 degrees are seen to be substituted in full by disparity changes. Possible implications of these findings for our vergence-body muscle interaction model is discussed and some preliminary EMG results are mentioned.

Evolutionary adaptations: Theoretical and practical implications for visual ergonomics

BACKGROUND The literature discussing visual ergonomics often mention that human vision is adapted to light emitted by the sun. However, theoretical and practical implications of this viewpoint is seldom discussed or taken into account. OBJECTIVE The paper discusses some of the main theoretical implications of an evolutionary approach to visual ergonomics. DISCUSSION Based on interactional theory and ideas from ecological psychology an evolutionary stress model is proposed as a theoretical framework for future research in ergonomics and human factors. The model stresses the importance of developing work environments that fits with our evolutionary adaptations. In accordance with evolutionary psychology, the environment of evolutionary adaptedness (EEA) and evolutionarily-novel environments (EN) are used as key concepts. Using work with visual display units (VDU) as an example, the paper discusses how this knowledge can be utilized in an ergonomic analysis of risk factors in the work environment. CONCLUSION The paper emphasises the importance of incorporating evolutionary theory in the field of ergonomics. Further, the paper encourages scientific practices that further our understanding of any phenomena beyond the borders of traditional proximal explanations.

Cognitive components and the ability to ignore and adapt to irrelevant stimuli: a key factor in open plan offices?

Employees differ in their apperception of open plan offices. Despite this, individual differences have been sparsely treated in the literature discussing effects of office design. The aim of the present study was to investigate how stimulus screening, working memory, and attention interrelate and affect important factors in the work environment. The study utilized a cross sectional design. Participants (N=35) were recruited among employees in four organizations. Working memory was assessed bye means of the Operation –Word Span Task (OSPAN) while attention was measured by the d2 test of attention. Dependent variables were job stress, job involvement, organizational commitment, and need for recovery. The results showed a main affect of stimulus screening on need for recovery and one subscale of organizational commitment. A main effect was also found for fluctuation rate across trials, a sub measure of attention, on need for recovery. The results revealed no indication of any mediator or moderator effects of either working memory or attention, on stimulus screening, for any of the dependent variables. Thus, the effect of stimulus screening seems not to be explained through individual differences in cognitive processes.

Vision and Body, Integrated Systems in Systemic Interplay

Based on an ecological analysis of the visual system, a systemic model is proposed linking visual stress and symptoms in other parts of the body. The model links the interaction between the oculomotor system and other body muscles to the slow-acting mechanism of Scohrs two-step theory of vergence control. Implications of the model have been examined in a field study. The results indicate that increased closeness between natural near work and VDU-work yield reduced symptomatology not only for eye symptoms but also for visually related symptoms in a broader sense.

Defining Sustainable and “Decent” Work for Human Factors and Ergonomics

Sustainable work is a vital factor in the transition towards global sustainability. The term itself, as well as its relations to work content, working conditions, and quality of life, is somewhat vague. In applying a resource management perspective, this chapter aims at bridging the long-term needs of the three main work-life stakeholders—individuals, enterprises, and society—to the economic, environmental, and social pillars of sustainability. A key factor in this regard is the reciprocity in values and goals between human factors and ergonomics and programmes promoting quality of work, such as the Decent Work Agenda. Sustainable work implies enabling workers to engage and develop throughout their career. To the authors, this seems impossible without facilitation of ideas and values linked to decent work.