Assessment of physical workloads to prevent work-related MSDs
Rolf Ellegast, Institute for Occupational Safety and Health of the German Social Accident Insurance
Physical workload factors and corresponding MSDs
At many workplaces, physical hazards are still an everyday occurrence. They are considered a risk factor for work-related musculoskeletal disorders (MSDs) that represent one of the most frequent causes of work-related incapacity to work in Europe. The estimated economic production loss due to MSDs is high.
For prevention of work-related MSDs risk assessment of physical workloads is an important part of the risk management process. It comprises a multistep approach to improve workplace health and safety and productivity. The general five steps of the risk assessment procedure involve identifying hazards and those at risk, evaluating and prioritising risks, decisions on preventive actions, executing actions and finally monitoring and reviewing at regular intervals.
To tackle work-related MSDs all five steps require precise knowledge of the physical workload factors and an estimate of the associated risks at workplaces. This involves recording physical workload factors associated with work-related musculoskeletal disorders in order, in a second step, to initiate the relevant ergonomic prevention measures.
Physical workload factors can be classified in the following categories:
- Manual material handling , e.g. lifting, holding, carrying, pulling and pushing
- Working in awkward postures (overload and underload), e.g. awkward trunk postures, crouching, kneeling, squatting, arms above shoulder level, lack of physical activity: sitting, standing, lying
- Repetitive work
- Work involving high exertion and/or exposure to force, e.g. climbing, knocking, hammering.
Table 1 shows these physical risk factor categories together with examples of corresponding work-related MSDs and sectors/occupational groups/tasks.
Table 1 – Physical workload factors with examples of corresponding work-related MSDs and associated sectors/occupations/tasks
|Physical workload factors||Examples of correspond-ding work-related MSDs||Examples of associated sectors/occupations/tasks|
|Manual materials handling:|
|Lifting, holding, carrying||Low Back Pain
Intervertebral lumbar disc disorders/injuries (e.g. protrusion, prolapse)
Lower Limb disorders, e.g. osteoarthritis of the hip and knee joints
|Construction sector: assembly of scaffolding, masonry work with blocks requiring handling with both hands, carpentry work|
Transport trades: vehicle maintenance, baggage handling work at airports
Agriculture, forestry, landscaping
|Pushing and pulling||Low Back Pain
Intervertebral lumbar disc disorders/injuries (e.g. protrusion, prolapse)
Neck Shoulder MSDs
|Nursing and health services: pushing and pulling of beds and wheelchairs|
Transport trades: pushing and pulling of trolleys on airliners, baggage handling work at airports, special tasks of aviation mechanics, domestic refuse disposal (refuse workers)
|Working in awkward postures:|
|Sitting without effective breaks/with lack of movement||Low Back Pain
Neck Shoulder MSDs
|Standing without effective relief||Lower Limb Disorders||Meat-processing industry: meat portioning|
Nursing and health services: sustained standing at operating tables, in some cases in conjunction with constrained postures
|Working in awkward trunk postures, static/dynamic, high proportion of the time||Low Back Pain
Intervertebral lumbar disc disorders/injuries (e.g. protrusion, prolapse)
|Metals industry: tank construction, shipbuilding, welding in confined spaces, visual weld inspection|
Mining: at faces with a free working height of less than approx. 160 cm
|Squatting, kneeling, lying||Lower Limb Disorders
Low Back Pain
|Mining sector: faceworker during extraction – work at the face at a free working height of up to approximately 120 cm|
Construction sector: floorers, roofers, tilers, plumbers, parquet layers
|Arms above shoulder level||Low Back Pain
Neck Shoulder MSDs
|Construction sector: decorating work, stucco workers and plasterers, plasterboard construction|
Automotive industry: special assembly work in the manufacture and maintenance of vehicles
|Repetitive tasks with high handling frequencies||Upper limb MSDs, e.g. Carpal Tunnelsyndrome, wrist tendinitis, and lateral epicondylitis||Trade, logistics and postal services: tasks in packaging and mail order, mail sorting offices, order-picking|
Food industry: for example fish and meat processing
|Work involving high exertion and/or exposure to force||Low Back Pain
Upper limb MSDs, e.g. Carpal Tunnelsyndrome, wrist tendinitis, and lateral epicondylitis
|Horticulture: tree care/felling with the use of rope-assisted tree-climbing techniques (basic and advanced)|
Construction sector: facade construction workers – erection of façades, scaffolding erection during work on special structures (bridges, towers)
According to the fifth European Working Condition Survey in 2010 the physical workload factors are still widely spread in the EU member states. For instance, a third of all workers reported that they have to carry heavy loads at least a quarter of their working time. Almost half of all polled workers indicated that they are working in awkward body postures. Some physical exposures differ for men and women, others not. Men are more regularly involved in manual material handling tasks, whereas no gender differences could be observed for repetitive tasks.
Assessment of physical workloads
Figure 1 shows the basic categories of methods for recording and assessment of physical workloads at the workplace with their potential user groups. The top category (Level 1) covers questionnaires and self reported data. In this category workers have to estimate retrospectively the occurrence and frequency of their daily amount of physical workload. Epidemiological studies on work-related MSDs often use self-reported data for exposure assessment. These methods are known as inaccurate workload assessments as the workers’ ability to estimate their physical exposure is limited and workers that already suffer from MSDs tend to overestimate their exposure. In the next category (Level 2) checklists are used to identify workload focused at the workplace. Normally checklists contain limiting values for the assessment of specific physical workload types. If these limiting values are exceeded, workload focuses can be identified.. Checklists are often used in combination with medical check-ups.
If workload focuses exist, such as the lifting and carrying of loads, it is advisable to employ more specific observational methods (Level 3) in order to assess the associated risk factors a little more precisely. Examples for screening observational methods in this category are the Finnish OWAS method and some newer methods like the Key Indicator Methods (KIM) and the MAC tool that address lifting and carrying, pulling and pushing and manual work processes and the ART tool for assessing repetitive tasks .
The observational screening methods afford simple, quick and practical application. For the recording and assessment of workloads of the upper extremities, additional methods such as the RULA method (Rapid Upper Limb Assessment), the OCRA method/OCRA checklist and the Hand Activity Level (HAL) are available.
The application of these methods is particularly suited to cyclic, uniform workload profiles at workplaces. Their application is limited in cases of the assessment of more complex work processes that are difficult to classify in the general workload categories. For certain types of work, such as activities involving physical exertion or awkward postures, there are few observational assessment methods. An example of an expert observational method for the assessment of activities involving physical exertion and/or exposure to force is the Exertion Atlas developed under the supervision of the Institute of Ergonomics of Darmstadt Technical University (IAD). For the assessment of different types of workload and particularly for cyclic activities in the automotive and supply industry, the IAD has developed the AAWS (Automotive Assembly Worksheet) and the EAWS (European Assembly Worksheet) in this category.
Observational methods are subject to the usual limitations of this category. The drawback of these methods is that they only roughly classify workload categories and often do not adequately reflect the complexity of work processes. In particular, three-dimensional movements, such as the torsion and lateral flexion of the back, can only be recorded with great inaccuracy using observation methods. Furthermore, it is not possible to appropriately record and assess the pattern of stressing and rest over time.
Therefore some applications necessitate the performance of measurements of physical workloads directly at the workplace (field measurements, Level 4). A number of measuring systems have been developed for the recording and analysis of body posture and movements in the work process. Most of these are designed specifically for the recording of the movement of parts of the body, e.g. the back. One example of a field measuring system that allows for long-time analyses (e.g. for an entire work shift) is the CUELA (“computer-aided recording and long-term analysis of musculoskeletal workloads”) measuring method. It permits the continuous recording and analysis of physical workload factors directly at the workplace. Given prior training, field measuring methods can be applied with a degree of effort comparable to that for the expert screening method. Depending on the application, the field measuring methods permit an assessment on the basis of biomechanical, energy/cardiopulmonary, muscular, psychophysical and epidemiological criteria. The limitations of measuring methods at the workplace include limitations in terms of the measurement accuracy (e.g. for measurements of exertion) characteristic of field measurements in real working conditions.
This is where laboratory measurements (Level 5) in which work processes are replicated under standardised experimental conditions yield the most precise data on the physical workload situation. Such laboratory measurements have been conducted for the analysis of several activities as nursing and for specific workloads.
Knowledge gaps and future activities
The presented methods of the various recording and assessment levels have been developed in most cases independently of one another and have rarely been combined. The precise principles for the assessment of each method have not always been disclosed in detail. Efforts should be made here to interlink the methods of all levels and precisely present the assessment principles. As a result it would be possible to identify gaps in the knowledge, develop the methods on all levels further and eliminate discrepancies in the assessment results.
Examples of gaps in the knowledge include the lack of approaches for the assessment of awkward postures and a consideration of both the risks of under-stimulation and of the pattern of stressing and rest (recovery phases) over time. The goal for prevention is to recommend the right degree of workload and thus prevent both occupational overload as well as under-stimulation, e.g. from lack of exercise.
For the assessment of the risks associated with specific work-related musculoskeletal diseases, e.g. Carpal Tunnel Syndrome (CTS), there is a need for assessment methods that do justice to the associated specific risk factors. Also relevant to CTS are assessments of the speed and frequency of wrist movements that are virtually impossible to determine using observational methods. One way of nevertheless obtaining near-authentic assessments involves compiling activity-specific exposure databases based on objective measured values. For the assessment of the knee-stressing activities associated with a high risk of inducing gonarthrosis, such a database has been established. Another advantage of these exposure databases is the possibility of using them in epidemiological studies. At present, exposure data on physical workloads in epidemiological studies are mainly recorded by questioning the persons concerned and are subject to the limitations of retrospective exposure recording. The inaccuracies associated with this could be reduced considerably by using exposure databases.
Along with physical workloads, it is important to take account of mental and psychosocial workloads that are associated with musculoskeletal disorders. Examples of this type of workload factors include:
- Highly demanding work
- Poor control/scope for decision-making
- Lack of social support (from superiors, colleagues)
- Insufficient gratification
- Dissatisfaction with work
- Workplace insecurity
The development of methods for the combined recording and assessment of physical and mental/psychosocial workloads at the workplace therefore represents a further important field of action.
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Links for further reading
EU-OSHA - European Agency for Safety and Health at Work, OSH in figures: Work-related musculoskeletal disorders in the EU - Facts and figures, Available at: 
EU-OSHA - European Agency for Safety and Health at Work, The human-machine interface as an emerging risk, Available at: 
EU-OSHA - European Agency for Safety and Health at Work, E-fact 45 - Checklist for preventing bad working postures, Available at: 
EU-OSHA - European Agency for Safety and Health at Work, E-fact 44 - Checklist for the prevention of manual handling risks, Available at: 
EU-OSHA - European Agency for Safety and Health at Work, E-fact 43 - Checklist for preventing WRULDs, Available at: 
EU-OSHA - European Agency for Safety and Health at Work, E-fact 42 - Checklist for prevention of lower limb disorders, Available at: 
EU-OSHA – European Agency for Safety and Health at work, Work-related musculoskeletal disorders: prevention report, 2008, Available at: