Trapezius muscle changes unrelated to static work load. Chemical and morphologic controlled studies of 22 women with and without neck pain.

From a cross-sectional study of 82 women who were engaged in assembly work that involved static muscle loading of the shoulder muscles, 11 cases with complaints of neck tension (all except 1 arising at work) and 11 individually matched, exposed control cases without neck pain were studied. In addition, 10 matched, unexposed control cases were studied. Upon histochemical examination and study of the trapezius muscle, morphologic changes of type ragged red fibers were found in 8/11 neck-pain cases, in 7/11 exposed controls, and in 4/10 unexposed controls. The pathologic and clinical importance of rare, ragged red fibers in the trapezius muscle thus seems uncertain.