Musculoskeletal disorders in visual display unit (VDU) tasks
Viorica Petreanu, Aurelia–Mihaela Seracin and Raluca Iordache, National Research - Development for Health and Safety, Romania
- 1 Introduction
- 2 Musculoskeletal disorder types in visual display unit tasks
- 3 Risks factors for musculoskeletal disorders in visual display unit tasks
- 4 Assessment and prevention of musculoskeletal disorders
- 5 Health surveillance
- 6 References
- 7 Links for future reading
The number of workers using a visual display unit (VDU) in their activity has increased continuously. Many office jobs are now dependent on the use of computers. Among the health issues resulting from VDU tasks there are musculoskeletal symptoms and disorders (MSDs). Various risk factors (physical, occupational, ergonomic, psychosocial and individual) interact in the development of these symptoms and disorders. This article aims to present some information regarding the main types of MSDs among computer workers, related risk factors, assessment and prevention of the MSDs in VDUs tasks.
Musculoskeletal disorder types in visual display unit tasks
Musculoskeletal disorders (MSDs) are impairments affecting some body structures such as muscles, joints, tendons, ligaments, nerves, bones and local circulatory system. They are pathologies of multifactorial aetiology caused and aggravated by the work organisation and performance together with environmental conditions.
MSDs are manifested by: discomfort, pain, stiffness, persistent muscle fatigue, muscle cramps, tingling and heaviness in extremities. In severe cases, there is a decrease of functional capacity to incapacity at the level of the affected area. Some MSDs are specific because of well-defined signs and symptoms (e.g. carpal tunnel syndrome, frozen shoulder). The others are non-specific where there is pain or discomfort, without specific symptoms. This does not mean that these symptoms have to be ignored. Musculoskeletal disorders can be an episodic disease because the pain often disappears and reappears after a few months or years. Some musculoskeletal disorders may become persistent or irreversible.
The most affected areas are: back (lumbar area), neck, shoulders, arms, hands and wrists, given the repetitive, static and intensive nature of the VDU work. All epidemiological surveys on VDU users report postural problems more frequent than in employees performing traditional office work. The main types of MSDs that may be encountered among VDU users include: tendonitis, tenosynovitis, bursitis, epicondylitis, channel syndrome of upper limbs.
Prevalence of musculoskeletal disorders among visual display unit workers
Visual display unit (VDU) tasks are diverse and present in a large range of jobs with different demands regarding the level of skills and knowledge (from journalists, financial administrators and so one to call centres and data processing workers). Communication via e-mail and instant messaging, the use of computer at home, increasing use of palm-held devices complete traditional computer work tasks. Based on the data of the 5th European Working Conditions Survey it can be clearly demonstrated that the number of workers that are using computers are increasing. In contrast, the proportion of those whose work is determined mainly by the use of machinery, and especially of those for whom the use of technology is not so important, is declining (Figure 1).
Figure 1 – The use of ICT at the workplace
Surveys found that a high proportion of visual display unit workers report complaints, pains or eye discomfort. In Europe, a number of cross-sectional studies on computer workers have reported a prevalence of 30-62% of musculoskeletal symptoms in the neck or shoulder region among VDU users . These complaints and pains can often be related to upper limb disorders . It should be noted that not always all reported musculoskeletal complaints are recorded as occupational disease. Most national systems only record specific diseases such as the carpal tunnel syndrome. However, data on occupational diseases do provide some indications about the prevalence of MSDs among computer workers. For example, in France it is estimated that 3-4% of the recognized musculoskeletal disorders (most of them as occupational diseases) can be attributed to visual display unit work  , 5-10% of upper limb MSDs recognized in France in 2006 may be attributed to VDU work .
Several studies suggested that an increased prevalence of upper extremity musculoskeletal symptoms may be associated with increased use of mouse. However, studies based on epidemiological data are scarce and often data are gathered based on subjective, self-reported, complaints. The few studies that do present epidemiological data found only limited evidence for a causal relationship between neck and upper limb MSDs and computer work .
Socio-economic consequences of musculoskeletal disorders are multiple: at individual (from sick leave to functional incapacity), organisation (absenteeism and turnover, increased number of days of sick leave, reduced performance, productivity and quality, high social and economic costs), and society level as a whole. At company level these are indicators for actions to be taken in order to reduce and eliminate the risks of occurrence and development of MSDs.
Risks factors for musculoskeletal disorders in visual display unit tasks
Physical load factors
Working with visual display units brings about biomechanical forces (physical load) that can generate the development of MSDs over time .
VDU workers mostly work in a (static) sitting posture. A prolonged sitting posture during VDU work could initiate continuous static contraction of the neck muscles, which may result in muscle overload, resulting in neck pain , upper limb disorders and back pain. Moreover, the general health risks of prolonged sitting time are becoming increasingly evident. Large epidemiological studies have shown that total sitting time is associated with increased risk of all-cause, cardiovascular and possibly cancer mortality. Especially an increase of all-cause mortality can be noticed around 7 or 8 h of self-reported sitting time per day .
Repetitive hand and wrist movements, stereotyped movements of the arms, hands and fingers in repetitive movements with short cycles, may determine increased rates of pain and MSDs. Repetitive loading cycles at high rates of maximum voluntary contraction lead to rapid onset of fatigue.
Equipment and workstation
Screen can be a source of risk factor when:
- it is placed too high/low/laterally in relation to operator;
- displayed elements are difficult to read (fonts too small, low contrast, etc.);
- the display allows reflections, the operator will try to turn his/her body to find a position where he/she does not see reflections, which can lead to a poor working posture;
- the unit is placed horizontally and the screen above it may be too high.
Keyboard and mouse use may involve risks because:
- the use of keyboard requires the depression of the keys, implying repetitive finger movements;
- the location, height and design of keyboard may affect posture of the wrist, elbow and shoulder;
- non neutral position of wrist has been reported as risk factor for arm, wrist and hand pain;
- repetitive clicking in addition to the sustained low level muscle activity when holding and moving the mouse may increase the muscle activity and tendon strain;
- non neutral postures of shoulder (flexion and abduction) are associated with MSDs of neck, shoulder and hand/arm;
- static effort of forearms without forearm support can lead to fatigue in the shoulder;
- manipulation of a mouse away from the keyboard favours the occurrence of pain to the wrist and shoulders; use of a mouse of an inadequate size/form or if tightly grabbed with the hand, may also be responsible for fingers MSDs;
- when documents are placed alongside the keyboard, the operator must turn and tilt his head to reduce the reading distance;
Work furniture and related equipment could be a risk source if:
- there are design and layout deficiencies of work desk, work surface, chair and document holder that could generate uncomfortable head and eyes movements, awkward positions;
- the work chair is not stable and does not allow easy freedom of movement and a comfortable position;
- there is not adequate space to allow workers to adopt a comfortable position;
- the seat is not adjustable in height and tilt;
- the footrest does not exist or it is inadequate.
Work space requirements: the workstation is not dimensioned and designed to provide sufficient space to user so that he/she cannot change position and vary movements.
The work time determines the cumulative biomechanical load and the degree of fatigue. It can be short and intense, leading to acute disorders, or prolonged with low/moderate intensities, leading to chronic or degenerative disorders.
Thus, postural pain is more common in case of data entry task than in dialogue task; an excessive typing speed and higher frequency of repetitive motions, a longer work time, in the first type of task, generates MSDs in the upper limbs. The dialogue task involves a more flexible and varied activity, freedom of movement. The number and content of work breaks are also important because if not organized properly (short and frequent breaks) they do not allow the relaxation of muscles and joints implied in operations achievement. The higher the pace and speed of work are the more insufficient and inefficient the recovery time is, leading to tension in muscles, tendons and joints.
New forms of technology
Since the widespread introduction of computing technologies into the office workplace, advances of new forms of technology have transformed the modern office workplace. Even desk top computers bear little resemblance to those available in the second half of the 1980s (when the DSE Directive was first drafted). There are widespread indications that technological developments in computer technologies have resulting in increasingly mobile devices, with novel interfaces (e.g. touch screens) becoming widely available and .being adopted within the workplace. The availability of equipment that no longer has to be used sitting at a desk in a dedicated office (such as laptop and tablet computers, together with internet-capable smartphones) has also resulted in radical developments in where and how that equipment is used, removing the constraints of the conventional office environment. Evidence suggests that these changes in technology and working practices still present risks to health and safety; but that the nature of those risks (both physical and psychosocial), and the requirements for managing them, are gradually changing as a result.
Psychosocial risk factors are involved in the development of musculoskeletal disorders, mainly through the state of stress, which causes an increase in the muscle tone. When workers are stressed, their muscles are more contracted than normal and cannot relax completely at rest. Stress increases the occurrence and changes characteristics of MSDs, increases pain, and makes operators more susceptible to other risk factors.
A number of different psychosocial factors are considered as risk factors for musculoskeletal disorders:
- High task demands – overload required to carry out the work: excessive work, conflicting demands, insufficient time to do work (time pressure, increased volume), work too fast etc.
- Some characteristics of task content can contribute to development of hand and wrist MSDs such as:
- monotonous tasks versus more varied tasks can cause neck pain;
- high level of concentration can cause muscle tension in hands and wrists;
- data entry tasks, similar to repetitive activities, versus dialogue tasks are more likely to cause psychosomatic disorders;
- a high cognitive load, an increasing mental strain, may contribute to muscle tension at shoulder.
- Lack of freedom to make decision and control over work task
- Professional development opportunity: lifelong learning, develop skills, perform a variety of tasks and that require creativity
- Role ambiguity – lack of clarity in work responsibilities and duties, work objectives not well defined
- Lack of social support provided by co-workers and supervisors, support that can make work life easier
- Role conflict – measure of conflicting demands addressed to worker.
In addition to occupational risk factors there are individual factors that also contribute to the risk of MSDs. They include: health state, physical and mental abilities, habits, lifestyle, posture and work habits, age, gender and working style.
Regarding health state, the people with medical conditions are more likely to develop MSDs. Examples of such conditions: joints with hypermobility, arthritis, diabetes mellitus or thyroid disease. History of back pain is also a factor in the forecast of future work related MSDs.
Reduced physical capacity and obesity make people more susceptible to MSDs. A reduced physical capacity is considered a strong risk factor of injury, and any feeling of fatigue a warning signal.
Musculoskeletal disorders (MSDs) and dorsal neck pain are more common among people who wear glasses.
The visual deficiencies can be a source of MSDs to workers who do not have a proper optical correction or any correction at all. The workers try to compensate their deficiencies approaching or distancing themselves from the screen by tilting the head, adopt abnormal head position with chin lift or keeping the head straight.
The older workers may be more susceptible to injury under high work demands. Wear of the body and especially of joints, along with age, reduced vision, are all individual factors inducing MSDs.
Women have been reported as having a higher incidence of MSDs  . However, there is no evidence that gender per se is a significant factor for the development of MSDs. The analysis of MSDs records shows that most disorders can be explained based on job characteristics. Women are for instance more often exposed to repetitive biomechanical stresses of the upper limb more than men. Also, the complex interplay between anthropometrics, work ability, productivity, and pain perception, may explain gender differences. A study among 690 Danish computer users for instance revealed that women often report poorer work ability and differences in pain perception than men . Explanations for the higher incidence among women can also be found in differences in household work and childcare, work situation, physical and psychosocial work conditions .
Assessment and prevention of musculoskeletal disorders
The first step in the preventive approach of musculoskeletal disorder risks is their identification and assessment in the work tasks. It is important to be systematic when carrying out a risk assessment and to take into account all aspects of the work situations. Workers should be involved in the risk assessment process. The most used tools to detect the MSDs risk factors are checklists/questionnaires. Risk assessment work sheets, guidance booklets can also be of help.
The MSDs are generally assessed through painful symptoms experienced by the operator. In many cases it is not possible to reveal any pathological modification at tissues level.
The musculoskeletal disorders risk prevention is an economic, social and moral need and, also, a legal obligation resulting from the risks assessment.
Generally, there are three stages of MSDs prevention:
- primary prevention – at the first occurrence of the MSD;
- secondary prevention – when a recurrence of symptoms is present;
- tertiary prevention – specific treatment and rehabilitation.
MSDs have a progressive occurrence and development and a multifactorial aetiology in which occupational risk factors are very important. Every improvement, at any level, will have a positive consequence on risk. The preventive approach should be an ergonomic one, in which the first stage is represented by risk assessment. Based on the risk assessment, measures should consider work organisation, workstation and workplace design, work environment, IT equipment (hardware and software). The provisions of Directive 90/270/EEC on display screen, keyboard, work desk or work surface, work chair, space, lighting, etc. should be applied . The measures should promote variation in working postures, e.g. variation between sitting and standing positions in the office by providing sit-stand desk, the introduction of regular breaks in static work by performing stretching and relaxing exercises and other measures to change ways to working to encourage getting up from the desk and moving around.
Therefore, the prevention approach includes different types of interventions at different levels:
- technical interventions (e.g. redesign, adjustment etc.);
- organisational interventions (e.g. breaks regime, work time, etc.);
- individual interventions (often individual approaches are needed);
- other types of interventions (e.g. health promotion, training etc.).
In visual display unit tasks a number of measures can be taken such as:
- ergonomic design and workplace layout, ergonomic work furniture (adjustable, adequate to different VDU tasks and individual differences) that helps workers to maintain a comfortable, neutral body posture with joints naturally aligned, and to reduce stress and strain on the muscles, tendons, and skeletal system, and to minimise the risk of developing MSDs;
- use of an ergonomic IT equipment (e.g. adjustable screen holder, short keyboard, various input devices) which ensure a more comfortable posture during the VDU work performance;
- adequate layout of the IT equipment components on the work surface in order to ensure a comfortable working position;
- ensure sufficient space at the workstation, to allow the operator to have a comfortable position, change his position, and move.
- ensure an adequate lighting, thermal comfort and low noise level at the workplace;
- adequate layout of the air conditioning equipment to prevent draught;
- computer work periodical interruptions through breaks and other non-IT activities; short and frequent breaks are preferable to long and rare ones; during the breaks, the operator should move out from the workstation, do relaxing exercises etc.;
- ensure a high level of work autonomy and adequate work pace;
- ensure work task variation in order to avoid monotony;
- avoid stress, peak working times, emergencies;
- training of workers on: correct techniques to adjust the work furniture, use of mouse and keyboard or other data input devices; use of work surface to ensure a comfortable, neutral work posture).
Interactive training techniques could add value to intervention programs for at-risk employees by improving their self-care and, possibly, for controlling musculoskeletal symptoms over time. A successful prevention approach means: determination, expertise, time and commitment of all actors involved.
Although there is a broad consensus about the prevention approach, little evidence is available on the effectiveness of these prevention measures. Findings from review studies on ergonomic interventions visual display unit users suggest that there is - moderate evidence that workplace adjustments have no effect on MSDs or visual outcomes ; - limited evidence that ergonomics training with workstation adjustments may be beneficial ; - mixed evidence on the effects of ergonomics training, arm supports, alternative keyboards and rest breaks on MSDs  - moderate evidence that alternative pointing devices have a positive effect on MSDs ; - moderate-quality evidence that the use of an arm support together with an alternative mouse may prevent work-related neck and shoulder disorders but not right upper limb disorders. The use of arm support alone or alternative mouse alone is not effective .
Complying the applicable legislation is important in preventing musculoskeletal disorders in visual display unit tasks. The Council Directive 90/270/EEC defines the minimum health and safety requirements for work with display screen equipment. These minimum requirements are designed to encourage improvements, especially in work environment, to ensure a better level of protection of safety and health for VDU workers . The directive obliges employers to perform a risk analysis of workstations, especially related to eyesight, physical problems and problems of mental stress and to take appropriate measures. All workers need to receive information and training related to their workstation and on the health and safety measures .
Further guidance on how to organise visual display unit work can be found in the multi-part Standard EN ISO 9241: Ergonomics of Human System Interaction. The ISO 9241 family which, when complete, will comprise more than 50 parts, with subjects ranging from electronic visual displays to physical input devices, dialogue techniques, interface control components, software accessibility, human-centred design, workstations and the work environment, application domains (control room/centre design/layout), and tactile and haptic interactions. All parts of the ISO 9241 are included in 1 of the 8 series (ranging from 100 to 900). Within each series several parts are available. The 300 series includes for instance all standard parts on Displays and display related hardware, e.g. ISO 9241-302 Terminology for electronic visual displays, and, ISO 9241-306 Field assessment methods for electronic visual displays. An overview can be found on the website of the International Organisation for Standardisation .
Visual display unit workers must be subject of an adequate medical surveillance in relation with specific risks in VDUs tasks. Monitoring the health state of personnel working with VDUs ensures early detection of any signs and symptoms. This way, corrective measures can be given before effects become irreversible. A way of monitoring personnel is a periodical medical control. This involves a general clinical exam with a focus on the musculoskeletal system and vision. Depending on the results of the clinical exam, the occupational physician can refer to a specialist. Also, he can make proposals on the workplace ergonomic adjustment or relocation of worker to another workplace.
Correction of visual issues also has a positive impact on adopting natural, comfortable work position. Education and training of personnel on VDU work related hygiene and health issues are also important.
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