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Introduction

To prevent work-related musculoskeletal disorders, it is necessary to record and assess physical workload factors at the workplace. Numerous methods are available for this, differing however in terms of the precision achieved in the recording and assessment of workload and in terms of user groups. This article gives a classification of physical workload factors and an overview of the basic categories of methods for recording and assessment. It cites examples of each category and highlights future fields of action.

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 [1]. The estimated economic production loss due to MSDs is high[2].

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[3]. 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.

For the recording and assessment of physical workload factors, numerous methods are available, ranging from interviews and surveys, field measurements and video-analysis up to laboratory measurements and simulations. However, these methods differ among other things in terms of the precision obtained in the recording and assessment of workloads and in terms of user groups. The assessment often targets the risk to a certain region of the body (e.g. the spine). The goal of this article is to classify physical workloads and to give an overview of principle methods for their recording and assessment.

Physical workload factors can be classified in the following categories:

  • Manual material handling, e.g. lifting, holding, carrying, pulling and pushing[4]
  • 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[2].

Table 1 – Physical workload factors with examples of corresponding work-related MSDs and associated sectors/occupations/tasks

Physical workload factorsExamples of corresponding work-related MSDsExamples of associated sectors/occupations/tasks
Manual handling:  
Lifting, holding, carryingLow 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
Metal industry: foundries/casting fettlers, metalwork
Nursing and health services: tasks in healthcare and geriatric care
Trade and logistics: warehousing, order-picking, transport work; parcel sorting
Pushing and pullingLow 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)
Landscaping: pushing and pulling of containers containing plants (loading)
Trade and logistics: warehousing, order-picking and transport work; pushing/pulling of trolleys in mail-order/postal operations
Cross-sector: pushing and pulling of carriages/trucks
Working in awkward postures:  
Sitting without effective breaks/with lack of movementLow Back Pain Neck Shoulder MSDsSpecific workplaces/tasks: Microscopy workplaces
Seated (primarily) activity at a process control system, control panel work
Tasks in drivers' cabs
Surveillance workplaces
Standing without effective reliefLower Limb DisordersMeat-processing industry: meat portioning
Nursing and health services: sustained standing at operating tables, in some cases in conjunction with constrained postures
Retail trade: sales tasks
Construction sector: carpenters
Working in awkward trunk postures, static/dynamic, high proportion of the timeLow 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
Construction sector: concrete technicians, steelfixers, composition floor layers, tilers, plumbers, bricklayers
Transport trades: aircraft loading personnel
Horticulture: vegetable harvesting, plant work, pruning work at ground level, grafting of roses, etc.
Children's daycare facilities: daycare facility staff
Squatting, kneeling, lyingLower Limb Disorders Low Back PainMining 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
Metals industry: welding in confined spaces (e.g. tanks, double bottoms, shipbuilding)
Cross-sector: work in poorly accessible places, e.g. in shipbuilding, turbine manufacture, aircraft manufacture
Arms above shoulder levelLow Back Pain Neck Shoulder MSDsConstruction sector: decorating work, stucco workers and plasterers, plasterboard construction
Automotive industry: special assembly work in the manufacture and maintenance of vehicles
Cross-sector: maintenance work
Repetitive tasks with high handling frequenciesUpper limb MSDs, e.g. Carpal Tunnelsyndrome, wrist tendinitis, and lateral epicondylitisTrade, logistics and postal services: tasks in packaging and mail order, mail sorting offices, order-picking
Food industry: for example fish and meat processing
Textile and clothing industry: sewing workplaces
Nursing and health services: masseurs
Work involving high exertion and/or exposure to forceLow Back Pain Upper limb MSDs, e.g. Carpal Tunnelsyndrome, wrist tendinitis, and lateral epicondylitisHorticulture: tree care/felling with the use of rope-assisted tree-climbing techniques (basic and advanced)
Construction sector: facade construction workers – erection of facades, scaffolding erection during work on special structures (bridges, towers)
Power supply works: maintenance for example of overhead lines, wind-power systems, transmitter towers

Source: [2]

Based on data from the Labour Force Survey (2013)[3] physical workload factors are still widely spread in the EU member states. Figure 1 shows the percentage of workers reporting exposure to risk factors that can adversely affect physical health. Handling loads and especially working in awkward postures are among the highest reported risk factors. According to the European Working Conditions Survey (EWCS) physical workload factors are still widely spread in the EU member states. A comparison between EWCS data from 2005, 2010, and 2015 shows a light decrease of exposure for (most of) the physical risk factors but European workers remain exposed to several physical hazards associated with MSDs. For instance, one third of the workers (32%) carry heavy loads at least a quarter of their working time, while almost one in five (20%) are exposed to vibration. Furthermore 40% of all workers work in tiring or painful postures for at least a quarter of the time, and 61% are exposed to repetitive hand or arm movements [5].

Figure 1 - Persons reporting exposure to risk factors that can adversely affect physical health by factor - EU-28 - 2013
Figure 1 - Persons reporting exposure to risk factors that can adversely affect physical health by factor - EU-28 - 2013

 

Assessment of physical workloads

Figure 2: Basic categories of methods for recording and assessment of physical workloads at the workplace and potential user groups
Figure 2: Basic categories of methods for recording and assessment of physical workloads at the workplace and potential user groups

Figure 2 shows the basic categories of methods for recording and assessment of physical workloads at the workplace with their potential user groups[2]. 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.[1]. Checklists are often used in combination with medical check-ups[2].

If a physical risk factor occurs, 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 more precisely. There are many examples of screening observational methods. For instance:

  • the Finnish OWAS method[3]. OWAS is the abbreviation of Ovako Working posture Assessment System. This method was first developed and introduced in Finland in a steel production company (Ovako) in the 1970s. Aspects to be observed include the weight of the load and postures of the back, arms, and lower extremities (seven postures).
  • the Key Indicator Methods (KIM)[4][5][5][6]. The KIM method was developed in Germany by the Federal Institute for occupational safety and health (Bundesanstalt für Arbeitsschutz und Arbeitsmedizin (BAUA)). The screening methods cover six types of workload: lifting, holding and carrying; pushing and pulling; manual handling operations; whole body forces; awkward postures and body movements. Tools and instructions on how to use the screening method are available in German, English, Spanish, French, Dutch and Swedish [7].
  • HSE. The Health and Safety executive (UK) presents three methods depending on the risk factor or type of activity.
    • the MAC tool [6](Manual handling Assessment Charts) addresses lifting and carrying, and manual handling operations. The method is based on a checklist and sets out 11 items of manual handling to be evaluated.
    • the ART tool (Assessment of Repetitive Tasks) is used for assessing repetitive tasks associated with upper limb disorders [9]. The ART tool uses a numerical score to indicate the level of risk for twelve factors grouped into four categories (frequency/repetition of movements; force; postures; additional factors such as duration).
    • the RAPP tool (Risk assessment of pushing and pulling) is used for pushing and pulling operations. The tool makes a distinction between pushing and pulling associated with moving loads on wheeled equipment (e.g. hand trolleys) and moving loads without wheels [10].
  • the RULA method[11] (Rapid Upper Limb Assessment). In the RULA method is based on the observation of the postures of individual body segments and then given a numerical value in relation to how far they deviate from the neutral position. Additional weights are given to the postures according to forces/loads handled and the occurrence of static/repetitive muscular activity.
  • the OCRA method/OCRA checklist[7][12] (Occupational Repetitive Action). The OCRA method is based on the observation of actions and the attribution of weights for six risk factors such as movement, posture, duration, force, …
  • the HALmethod [8] (Hand Activity Level). The HALmethod is developed by the American Conference of Governmental Industrial Hygienists and can be used for the evaluation of job risk factors associated with musculoskeletal disorders of the hand and wrist. The evaluation is based an assessment of hand activity and the level of effort for a typical posture while performing a short cycle task.

The observational screening methods are simple, quick and practical to use. The application of these methods is particularly suited to cyclic, uniform workload profiles at workplaces. A systematic review and comparison of observational methods assessing biomechanical exposures in occupational settings has been published in [11]. 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)[13] and the EAWS (European Assembly Worksheet)[14] 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[9]. 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[10]. 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[11][12]. 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[13][2]. 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[16][14][15].

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 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.

Furthermore, there is a need to review the applicability and validity of ergonomic assessment methods for assessing tasks when workers are using exoskeletons in the workplace [17]. Exoskeletons reduce the exposure to specific physical demands (e.g. force of the upper limbs), but the biomechanical load might shift to other joints or muscle groups [18]. These effects have to be taken into account and integrated in the assessment methods in order to fully evaluate the physical load and associated risks [19].

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[1]. 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
  • Monotony

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.

Références

[1] EU-OSHA – European Agency for Safety and Health at Work, Work-related musculoskeletal disorders: prevalence, costs and demographics in the EU, 2019. Available at: https://osha.europa.eu/en/publications/msds-facts-and-figures-overview-prevalence-costs-and-demographics-msds-europe/view

[2] IFA – Institute for Occupational Safety and Health of the German Social Accident Insurance, ''Entwicklung und Evaluation eines Bewegungsmesssystems zur Analyse der physischen Aktivität. IFA-Report 2/2011''. Available at https://publikationen.dguv.de/forschung/ifa/ifa-report/2454/entwicklung-und-evaluation-eines-bewegungsmesssystems-zur-analyse-der-physischen-aktivitaet.-ifa-repo

[3] Eurostat (2020). Persons reporting exposure to risk factors that can adversely affect physical health by sex, age and factor (hsw_exp4). Last update 14/09/2023. Retrieved 3 October 2023, from: https://ec.europa.eu/eurostat/databrowser/product/page/HSW_EXP4

[4] Steinberg, U., Behrendt, S., Caffier, G., Schultz, K., Jakob, M., ''Leitmerkmalmethode Manuelle Arbeitsprozesse. Erarbeitung und Anwendungserprobung einer Handlungshilfe zur Beurteilung der Arbeitsbedingungen'', Bundesanstalt für Arbeitsschutz und Arbeitsmedizin, Dortmund, 2007.

[5] Steinberg, U., 'New tools in Germany: development and appliance of the first two KIM ("lifting, holding and carrying" and "pulling and pushing") and practical use of these methods', ''Work: A Journal of Prevention, Assessment and Rehabilitation'', 2012, 41, pp. 3990-3996

[6] MEGAPHYS - Mehrstufige Gefährdungsanalyse physischer Belastungen am Arbeitsplatz. Band 1, Bundesanstalt für Arbeitsschutz und Arbeitsmedizin 2019. Project number: F 2333. Available at: https://www.baua.de/EN/Service/Publications/Report/F2333.html

[7] BAUA, KIM method. Available at: https://www.baua.de/EN/Topics/Work-design/Risk-assessment/Key-indicator-method/Key-indicator-method_node.html

[8] HSE – Health and Safety Executive, Manual handling assessment chart (MAC) tool (2003). Available at http://www.hse.gov.uk/msd/mac/index.htm

[9] HSE – Health and Safety Executive, Assessment of Repetitive Tasks (ART) tool. Available at http://www.hse.gov.uk/msd/uld/art/index.htm

[10] HSE – Health and Safety Executive, RAPP tool – pushing and pulling loads. Available at: https://www.hse.gov.uk/msd/pushpull/index.htm

[11] Takala E-., Pehkonen I., Forsman M., Hansson G-Å., Mathiassen SE., Neumann WP., Sjøgaard G., Veiersted KB., Westgaard RH., Winkel J., Systematic evaluation of observational methods assessing biomechanical exposures at work, Scandinivian Journal of Work, Environment and Health, 2010;36(1), pp. 3-24. Available at: https://www.sjweh.fi/show_abstract.php?abstract_id=2876

[12] Antonucci A., Comparative analysis of three methods of risk assessment for repetitive movements of the upper limbs: OCRA index, ACGIH(TLV), and strain index, International Journal of Industrial Ergonomics, vol. 70, March 2019, pp. 9-21. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0169814117300422

[13] Schaub, K., ’Das „Automotive Assembly Worksheet" (AAWS)’, Landau, K., ''Montageprozesse gestalten: Fallbeispiele aus Ergonomie und Organisation'', Stuttgart, Ergonomia-Verlag, 2004, pp. 91-111.

[14] Schaub, K., Caragnano, G., Britzke, B., Bruder, R., ‘The European Assembly Worksheet’, Mondelo, P., Karwowski, W., Saarela, K., Swuste, P., Occhippinti, E., ''Proceedings of the VIII International Conference on Occupational Risk Prevention'', ORP 2010, Valencia 5.-7.5.2010, (CD-Rom).

[15] Marras, W. S., Fathallah, F. A., Miller, R. J., Davis, S. W., Mirka, G. A., ‘Accuracy of a three-dimensional lumbar motion monitor for recording dynamic trunk motion characteristics’, ''International Journal of Industrial Ergonomics'', 9, 1992, pp. 75-87.

[16] Jäger, M., Theilmeier, A., Jordan, C., Luttmann, A., ‘Dortmunder Lumbalbelastungsstudie 3 – Ermittlung der Belastung der Lendenwirbelsäule bei ausgewählten Pflegetätigkeiten mit Patiententransfer. Teil 3: Biomechanische Beurteilung von Tätigkeiten im Gesundheitsdienst hinsichtlich der Möglichkeiten zur Prävention von Gefährdungen der Wirbelsäule‘, Shaker, Aachen, 2008.

[17] EU-OSHA - European Agency for Safety and Health at Work,The impact of using exoskeletons on occupational safety and health, 2019. Available at: https://osha.europa.eu/en/publications/impact-using-exoskeletons-occupational-safety-and-health/view

[18] Theurel, J., Desbrosses, K., Occupational Exoskeletons: Overview of Their Benefits and Limitations in Preventing Work-Related Musculoskeletal Disorders, IISE Transactions on Occupational Ergonomics and Human Factors, 2019, 7, pp. 264–280. Available at: https://www.tandfonline.com/doi/full/10.1080/24725838.2019.1638331

[19] Dahmen, C., Hefferle, M., Application of Ergonomic Assessment Methods on an Exoskeleton Centered Workplace, Proceedings of the XXXth Annual Occupational Ergonomics and Safety Conference Pittsburgh, Pennsylvania, USA, June 7-8, 2018. Available at: https://pdfs.semanticscholar.org/b17a/e8cb3e6b1709f1aae81a481a93649b7eb042.pdf

Lectures complémentaires

EU-OSHA - European Agency for Safety and Health at Work, Practical tools and guidance on musculoskeletal disorders, Available at: https://osha.europa.eu/en/themes/musculoskeletal-disorders/practical-tools-musculoskeletal-disorders

EU-OSHA - European Agency for Safety and Health at Work, Healthy workers, thriving companies - a practical guide to wellbeing at work, Available at: https://osha.europa.eu/en/publications/healthy-workers-thriving-companies-practical-guide-wellbeing-work/view

EU-OSHA - European Agency for Safety and Health at Work, Conversation starters for workplace discussions about musculoskeletal disorders, Available at: https://osha.europa.eu/en/publications/conversation-starters-workplace-discussions-about-musculoskeletal-disorders/view

EU-OSHA – European Agency for Safety and Health at Work, Work-related musculoskeletal disorders: prevalence, costs and demographics in the EU, 2019. Available at: https://osha.europa.eu/en/publications/msds-facts-and-figures-overview-prevalence-costs-and-demographics-msds-europe/view

EU-OSHA - European Agency for Safety and Health at Work,The impact of using exoskeletons on occupational safety and health, 2019. Available at: https://osha.europa.eu/en/publications/impact-using-exoskeletons-occupational-safety-and-health/view

EU-OSHA - European Agency for Safety and Health at Work, The human-machine interface as an emerging risk, Available at: https://osha.europa.eu/en/publications/literature_reviews/HMI_emerging_risk/view

EU-OSHA - European Agency for Safety and Health at Work, E-fact 45 - Checklist for preventing bad working postures, Available at: https://osha.europa.eu/en/publications/e-facts/efact45/view

EU-OSHA - European Agency for Safety and Health at Work, E-fact 44 - Checklist for the prevention of manual handling risks, Available at: https://osha.europa.eu/en/publications/e-facts/efact44/view

EU-OSHA - European Agency for Safety and Health at Work, E-fact 43 - Checklist for preventing WRULDs, Available at: https://osha.europa.eu/en/publications/e-facts/efact43/view

EU-OSHA - European Agency for Safety and Health at Work, E-fact 42 - Checklist for prevention of lower limb disorders, Available at: https://osha.europa.eu/en/publications/e-facts/efact42/view

EU-OSHA – European Agency for Safety and Health at work, Work-related musculoskeletal disorders: prevention report, 2008, Available at: https://osha.europa.eu/en/publications/reports/en_TE8107132ENC.pdf/view

Contributeur

Karla Van den Broek

Prevent, Belgium
Klaus Kuhl

Rolf Ellegast

Ruth Klueser