Author(s): KRAMPE, L., SCINICARELLI, G., HANSEN, L., PETERS, D., WOLLESEN, B., Institution: GERMAN SPORT UNIVERSITY COLOGNE, Country: GERMANY, Abstract-ID: 480

INTRODUCTION:
Prolonged static sitting is particularly common among office workers and has been shown to be associated with musculoskeletal complaints and reduced well-being [1]. The primary causes are unilateral biomechanical stress and muscle activation patterns. Although surface electromyography (sEMG) studies provide important data on muscle activity and fatigue, the exact interactions between posture, muscular response, and physical discomfort have not yet been sufficiently clarified. The aim of this study is to systematically investigate these relationships in order to improve the basis for effective ergonomic prevention measures.
METHODS:
24 healthy subjects (50% male, 50% female; age: 28 ± 5 years) with predominantly sedentary occupations were examined in twelve independent, standardised sitting postures for four minutes each [2]. The dependent variables included muscle activity (sEMG: M. cervicalis, M. trapezius, M. erector spinae, M. obliquus) and subjective discomfort (Borg CR10). Signal processing was performed using Python (v.3.11.9), incorporating Butterworth band-pass and notch filters, RMS calculations (400 ms window), and outlier removal (±3SD), with all data normalised to a neutral reference position (defined as an upright posture with 90° angles). Statistical analysis was performed using repeated measures analysis of variance (α = .05).
RESULTS:
Compared to neutral sitting, specific standardised postures led to posture-dependent shifts in muscle activity (p < .05 to .001; r = .47 to .82). Borg scale ratings showed significant deviation from neutral sitting, with at least one significant change observed in every position (p < .05 to 0.001). However, correlation analyses show that the relationship between objective muscle activity and subjective perception varies greatly depending on position and muscle (r = -.52 to .76), and does not follow a universal trend.
CONCLUSION:
The twelve specified sitting positions represent only a limited selection of actual sitting postures, as mixed forms that are natural and dynamic often occur in everyday life. Nevertheless, working freely at a desk with a mouse and keyboard under standardised laboratory conditions allowed for practical data collection. It is recommended to promote active sitting with regular changes in posture in order to variably load different muscle groups and reduce one-sided strain.
REFERENCES:
Gao, W., Sanna, M., Chen, Y. H., Tsai, M. K., & Wen, C. P. (2024). Occupational sitting time, leisure physical activity, and all-cause and cardiovascular disease mortality. JAMA network open, 7(1), e2350680-e2350680.
Tahernejad, S., Razeghi, M., Abdoli-Eramaki, M., Parsaei, H., Seif, M., & Choobineh, A. (2023). Recommended maximum holding time of common static sitting postures of office workers. Interna-tional Journal of Occupational Safety and Ergonomics, 29(2), 847-854.