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Pathological mechanisms implicated in localized female trapezius myalgia
Fawzi Kadi1, Kerstin Waling, Christina Ahlgren
1Department of Anatomy, Umeå University, S-901 87, Umeå, Sweden Laboratoire de Physiologie et Biologie de la Motricité. URA CNRS 1448, UFR Biomédicale des St Pères, 75005, Paris, France Department of Musculoskeletal Research, National Institute for Working Life, Umeå University, S-901 87, Umeå, Sweden Department of Occupational and Environmental Medicine, Umeå University, S-901 87, Umeå, Sweden Department of Plastic Surgery, Norrland University Hospital, 901 87 Umeå, Sweden.
Work-related neck and shoulder myalgia in women is linked to muscle fiber changes. Specifically, larger type I fibers and reduced capillary supply in trapezius muscles correlate with increased pain intensity.
Area of Science:
- Occupational health
- Muscle physiology
- Pain research
Background:
- Neck and shoulder myalgia is a prevalent issue, particularly in working women.
- Understanding the underlying mechanisms of work-related myalgia is crucial for effective intervention.
Purpose of the Study:
- To investigate the morphologic and metabolic characteristics of trapezius muscle fibers in women experiencing myalgia.
- To identify potential physiological factors contributing to work-related neck and shoulder pain.
Main Methods:
- Muscle biopsies were taken from the upper trapezius of 21 women with myalgia.
- Muscle fiber morphology and metabolic markers, including capillary-to-fiber ratio and cytochrome c oxidase (COX) activity, were analyzed.
- Pain intensity and affected areas were quantified using a visual analogue scale (VAS) and pain drawing.
Main Results:
- Trapezius muscles showed large type I fibers and a low capillary-to-fiber area ratio.
- A lower capillary-to-fiber area ratio in type I fibers correlated with higher pain scores (r = -0.45, P < 0.05).
- A higher proportion of COX-negative fibers was observed in patients with greater pain and more painful areas (P < 0.05).
Conclusions:
- Increased type I fiber size suggests specific strain on these fibers during occupational tasks.
- Cytochrome c oxidase deficiency indicates an energy deficit within muscle cells.
- Low capillary-to-fiber ratio may impair oxygen supply and metabolite removal, contributing to trapezius myalgia.