Objective: Trapezius myalgia or, more specifically, myofascial dysfunction of the upper trapezius mainly affects women performing jobs requiring prolonged low level activation of the muscle. This continuous low muscle load can be accompanied by a shift to a more anaerobic energy metabolism, causing pain. The aim of the study was to investigate whether morphological signs of an impaired aerobic metabolism are present in female office workers with trapezius myalgia.
Design: Muscle biopsy analysis, using electron and light microscopy, was performed to compare mitochondrial and fat droplet morphology, and irregular muscle fibers, between female office workers with (n = 17) and without (n = 15) work-related trapezius myalgia.
Results: The patient group showed a significantly higher mean area (P = 0.023) and proportion (P = 0.029) for the subsarcolemmal and intermyofibrillar mitochondria respectively, compared with the control group. A significantly lower mean area of subsarcolemmal lipid droplets was found in the patient group (P = 0.015), which also displayed a significantly higher proportion of lipid droplets touching the mitochondria (P = 0.035). A significantly higher amount of muscle fibers with cytochrome c oxidase-deficient areas were found in the patient group (P = 0.030).
Conclusions: The results of the present study may be indicative for an impaired oxidative metabolism in work-related trapezius myalgia. However, additional research is necessary to confirm this hypothesis.