¹Institute of Occupational and Social Medicine and Health Services Research, University Hospital of Tübingen, Tübingen, Germany
²Department of Sports Medicine, University Hospital Tübingen, Tübingen, Germany
³Interfaculty Research Institute for Sports and Physical Activity, Eberhard Karls University of Tübingen, Tübingen, Germany
⁴HOT Screen GmbH, Reutlingen, Germany

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Introduction: Work-related musculoskeletal disorders (WRMSD) are prevalent in occupations characterised by high repetition and high force demands. Both factors do not only evoke inflammatory and degenerative processes in the affected musculoskeletal tissue, but also systemic responses identified by biomarkers in blood serum. Clarifying methodological aspects of systemic inflammatory biomarkers may provide insights into their predictive role in the pathway of developing WRMSD. This pilot study will primarily assess the reliability of systemic inflammatory biomarkers (CRP, IL-1β, IL-6, TNF-α) and immune cell reactivity by repeated measures in workers with constant workloads over time.

Methods: This methodological study will include an exposed group consisting of 20 workers (half men) exposed to higher upper-extremity physical workloads and an unexposed group consisting of 20 office workers (half men) exposed to lower upper-extremity physical workloads. Study participants undergo nine repeated measurements in a biweekly mode, taking blood samples among others. Blood analyses will determine values of systemic inflammatory biomarkers (enzymatic-photometric analysis & enzyme-linked immunosorbent assay) and reactivity of immune cells (TruCulture^® plus Luminex^® xMAP^® technology). The relative test-retest reliability of the biomarkers and immune cell reactivity over time is assessed by the intraclass correlation coefficient applying two-way mixed-effects models. The absolute test-retest reliability is assessed by the standard error of measurement. Secondary outcomes collected repeatedly along with the blood samples include ratings of perceived pain and pressure pain thresholds in the forearm-wrist-hand area. This trial is registered at the German Clinical Trials Register (Identifier: DRKS00031872).

Results: For organisational reasons, we had to plan two measurement periods. The first period started in January 2025 with eleven participants in the exposed group and nine participants in the non-exposed group. The measurement period, in which we aim for nine repeated measurements per participant, will end in May 2025. The second period is currently planned to start in June 2025 and end in October 2025, if we are able to recruit and include sufficient participants by then. The blood analyses are performed after both measurement periods have ended.

Experiences: The major challenge is in participant recruitment because it is predominantly based on cold acquisition and because of the intensive and complex study design. The challenging recruitment as well as preliminary results of the secondary outcomes will be presented at the conference.

Discussion: The knowledge of and models currently describing the pathological role of systemic inflammatory biomarkers are based on highly controlled laboratory rat experiments. This study has the strength that it assesses a human population under real-life conditions. The results of this study are expected to provide fundamentals for initiating a future epidemiological cohort study and be used in the longer term for developing work-related stress-recovery concepts for occupations with different physical demands to identify workers who may be at risk for developing WRMSD.