Prevention and treatment of work-related musculoskeletal disorders through a holistic understanding of biomechanical and psychosocial factors in occupational and clinical practice

Status:

completed

Aims:

Despite a steady increase in findings in the field of human factors and a multitude of large-scale initiatives, the proportion of working days lost due to incapacity for work caused by musculoskeletal disorders has remained at a high level over the last ten years, accounting for around 25%. The discrete risk factors for work-related musculoskeletal complaints and disorders can be divided into three categories: physical exposures, psychosocial stressors and factors specific to the individual person. Among the physical risk factors are the effects of external forces, repetition and constrained postures. Many physical risk factors for the incidence of musculoskeletal complaints and disorders are already known, but are often recorded only in qualitative terms. Furthermore, the analyses of stress parameters in most biomechanical studies focus primarily on specific regions of the body. Consequently, possible interactions between the stress parameters (e.g. the combined effect of asymmetrical execution of movement and the effect of force) and between the body regions (e.g. transfer of stress to other, adjacent body regions owing to variations in performance of the activity and load weights) are rarely included. Sustainable prevention of work-related musculoskeletal complaints and disorders therefore requires further findings that can be used to formulate quantifiable stress factors and intervention approaches for the relevant influencing factors. For these reasons, a promising strategy would appear to be to focus on research into the discrete risk factors for work-related musculoskeletal complaints and disorders and the associated stress factors. The preventive measures that can potentially be derived from the results lend themselves well to implementation in companies.

The joint workHealth project funded by the German Federal Ministry of Education and Research (BMBF) on the "Prevention and treatment of work-related musculoskeletal disorders through a holistic understanding of biomechanical and psychosocial factors in occupational and clinical practice" is being conducted jointly by a research network drawn from the disciplines of medicine, orthopaedics, physiotherapy, biomechanics, health psychology, ergonomics and human factors. The focus of the joint project lies in the first instance on activities placing stress on three localizations in particular: the lumbar spine, hip and knee. To permit a holistic approach, the biomechanical stresses arising are determined over the entire body, beyond the focus on the relevant body regions. The IFA’s involvement is focused on two sub-projects (SPs).

SP4 concerns the identification, recording and analysis of activities giving rise to physical stress. Work in this sub-project is being conducted in cooperation with the Clinic of Anaesthesiology at the UMG University Medical Centre of the Georg August University of Göttingen. TP6 is being conducted in cooperation with the Institute of Industrial Engineering and Ergonomics at RWTH Aachen University, the Clinic for Orthopaedics at Aachen University Hospital and Audi AG. The aim is the further development of methods in which calculable (stress) conditions such as joint angles, joint moments, body postures and movement speeds are used for continuous data acquisition and direct biofeedback on the stress on human joints.

These two SPs are intended to make a significant contribution to the further development, trialling and optimization of existing measurement-based risk assessments of work-related physical exposures (CUELA method: computer-based measurement and long-term analysis of stresses upon the musculoskeletal system), intervention measures (including exoskeletons) for reduction of biomechanical or psychosocial overload, and prevention approaches for transfer of the findings to the field.

Activities/Methods:

In SP4, workplaces involving industrial activities were selected that are particularly considered to place stress upon a certain body region owing to the specific tasks associated with them.

Critical stresses upon the musculoskeletal system were to be identified, analysed and correlated with work-related musculoskeletal complaints in laboratory and field studies, with consideration also being given to the psychosocial and physical factors specific to the test person that were determined in the studies. The activities were selected based on findings and data drawn from the IFA’s existing exposure data (CUELA data) and a recent literature survey. In addition, common patterns were to be sought that may enable conclusions to be drawn regarding exposure in other, similar activities.

The identified activities and their primary characteristics were simulated during the preceding laboratory phase, enabling an extended stress profile of the activity to be recorded and described. The main objective of the laboratory study was to record, as precisely as possible, the biomechanical stress factors extending across multiple regions of the body. The body movements and external reaction forces were recorded by means of a marker-based movement recording system (including force sensors). The biomechanical stresses arising on and within the joints were calculated by the use of digital human models, based on force/moment progressions over time. In addition, the variations in performance of the activity (e.g. height of load acceptance, height of load placement, forms and speeds of execution) were to be studied with regard to their influence on the stress profile. Technical intervention measures, such as the use of exoskeletons, were also taken into account. The field measurements enabled the stress factors to be studied under real-case conditions, which is not possible in laboratory studies. The biomechanical stresses occurring in different regions of the body during the activity studied were determined by means of the CUELA mobile movement recording and analysis system and correlated with the psychosocial stresses determined by the project partner.

In SP6, the criteria to be met by mobile motion capture systems were gathered in interviews and workshops conducted with the project partners, and recorded in a functional specification document. The mobile systems (e.g. CUELA) were optimized and validated for use in professional practice according to the requirements by means of the available measurement technology, e.g. the Vicon system.

Results:

As part of SP6, recordings of human movements during work were linked to real-time feedback on the stresses on the lower back and shoulders. The person being studied thus receives direct feedback on a body posture or stress on the body that is potentially ergonomically unfavourable. The methods required for assessment of the body posture and stress on the body were developed further and implemented in the course of SP6. With reference to the latest scientific literature and in consideration of prevention aspects, new and existing measurement-based assessment methods for the lower back and the shoulder joints were created or developed further. The resulting measurement-based approaches to assessment are based on the identified risk factors, in connection with elevated musculoskeletal stress and the musculoskeletal complaints or disorders of the individual regions of the human body to which they may have given rise.

Activities involving stress and the associated musculoskeletal complaints were identified, recorded and analysed in the course of SP4. Factors specific to the work and physical and psychosocial factors specific to the person were also taken into account. The overarching and primary objective of SP4 was the combined recording and assessment of physical stresses at the workplace, and psychosocial factors. During the study, 29 test persons from three different sectors (production, logistics, maintenance & transport) were studied with regard to the biomechanical stress caused by their workplaces and their psychosocial, workplace-specific and person-specific stress. The results of the biomechanical studies were assessed with the aid of the up-to-date ergonomic assessment methods which had been developed further as part of SP6. The psychosocial and workplace-specific factors were then placed in relation to their cut-off values as stated in the questionnaire. During the study, the individual parameters for each test person were first recorded, assessed, and finally summarized in their corresponding grouping. The influence of the respective factors on pain could not be determined clearly from the recorded parameters, as the development of musculoskeletal complaints must be viewed in the biopsychosocial model as the result of multifactorial causes. The random sample is too small for the magnitude of each individual factor’s influence to be determined clearly. Nevertheless, the results provide information on the scale of musculoskeletal complaints in the random sample, the psychosocial, workplace-specific and person-specific stresses experienced by the employees, and the physical stress caused by the workplaces.

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