Fiber type composition of the human female trapezius muscle: Enzyme‐histochemical characteristics

Abstract

Tne anatomy of the human trapezius muscle is complex, with an extensive origin and fibers running in different directions. The muscle is commonly divided into three different muscle portions according to the fiber direction: the descending, transverse, and ascending portions. In a previous study in males, the structure of the muscle differed between different portions with respect to the enzyme-histochemical fiber-type profile. The lower regions of the descending portion and the transverse and the ascending portions had a predominance of type I fibers. The type II fibers were more frequent in the upper regions of the descending portion, and the cross-sectional fiber area in this region of the muscle was smaller. In this study, we have investigated the trapezius muscle in females and compared the results with those from males. The different portions of the female muscle had a relatively even fiber-type composition. However, there tended to be fewer type I fibers and more type IIB fibers in the descending portion of the muscle, and the fibers of the lower regions of the descending portion were somewhat larger. The fiber-type distribution pattern was similar to that of the male trapezius muscle, but the mean cross-sectional area of the fibers in the female muscle was considerably smaller. Thus, our conclusion is that the trapezius muscle of females has a similar activity pattern as that of males. The significantly smaller cross-sectional fiber area, however, may indicate a lower functional capacity which may be of importance in the development of neck and shoulder dysfunction in females.

Changes in muscle morphology in chronic trapezius myalgia.

“…There are, however, difficulties associated with studying the trapezius muscle which may to some extent explain the discrepancies between the two observations, and perhaps also between the two groups in the present study. As we have previously shown, the muscle fiber composition of the trapezius muscle is inconsistent throughout different portions of the muscle, the inconsistency being most apparent in the descending portion of the muscle (38,39). In the lower regions of the descending portion type I fibers predominate, and the fibers have a larger cross-sectional area.…”

“…Interestingly, biopsies obtained from male subjects with the same symptoms all showed normal ATP levels (our unpublished results). This phenomenon might indicate differences between men and women with respect to muscle function and work tolerance , as has previously been suggested (39).…”

“…They are found only in the type I fiber population and only in the descending portion of the muscle (38,39). It is suggested that the specific anatomic location of these fibers may indicate that this region of the muscle is subjected to strain even during ordinary conditions with no excessive loading (38,46).…”

Neck–Upper Extremity Musculoskeletal Disorders Among Workers in the Telecommunications Company at Mansoura City

“…In office work, static loading of the neck coupled with dynamic repetitive movements of the wrists and hands are common triggering factors for neck-shoulder complaints particularly among VDT users due to prolonged muscular isometric contraction [20]. Psychosocial exposure at work, such as fear of being replaced with computers [5] and low social support [9], may preferentially affect muscles of the neckshoulder region.…”

Work-related Reproductive, Musculoskeletal and Mental Disorders among Working Women-History, Current Issues and Future Research Directions.

“…We cannot find any studies in Japan that answer the question clearly. Even in foreign studies, the factor of gender difference in the incidence is not clear yet, but some studies suggest that muscle fiber composition in the trapezius muscle may be related to the gender difference 41,42) . It has been reported that the composition of type 1 fibers, related to myofacial pain, in women's trapezius muscles is higher than in men (Table 5).…”