Morphological differences in the upper trapezius muscle between female office workers with and without trapezius myalgia: facts or fiction? A cross-sectional study

Objective Work-related trapezius myalgia is a common musculoskeletal disorder in office workers. Prolonged low-level muscle activity during office work may lead to morphological changes in the muscle tissue, causing pain and fatigue. The aim of the present study was to investigate differences in muscle morphology between office workers with and without trapezius myalgia. Design Muscle biopsy samples were obtained from the upper trapezius of female office workers with trapezius myalgia (n=17) and healthy controls (n=15). Myosin heavy chain immunohistochemistry and Gomori trichrome stainings were performed to identify differences in muscle fiber type proportion, Feret's diameter and internal nuclear proportion. Results The myalgia group showed significantly more type IIA and IIA/IIX fibers, and less type I and IIX fibers, compared to the control group (P0.05). However, a significantly higher Feret's diameter was found for type I fibers, compared to type II fibers in both groups (P

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