engleski

Fibre type composition of the human psoas major muscle with regards to the level of its origin

The aim of our study was to explore fibre type composition of the human psoas muscle on different levels of its origin, starting from the first lumbar to fourth lumbar vertebra and to compare muscle fibre size and distribution of different fibre types between levels with respect to its complex postural and dynamic function. Muscle samples were collected from 15 young males (younger than 35 years). Serial transverse sections (5 m) of the samples were cut by cryomicrotome. Type I, IIA and IIX muscle fibers were typed using myosin heavy chain identification. Serial sections were analised using light microscope with magnitude of 100x. Differences between measurements were evaluated using repeated-measures analysis of variance and Scheffé test for Post Hoc analysis. Our study has shown that the human psoas major muscle is composed of type I, IIA and IIX muscle fibres. It has predominance of type IIA muscle fibres while type I muscle fibres has biggest cross-sectional area. Type IIX muscle fibres are present in far less percentage and have the smallest cross-sectional area. Moreover, fibre type composition of psoas muscle is different between levels of his origin starting from first lumbar to fourth lumbar vertebra. We concluded that fibre type composition of the psoas muscle indicates its dynamic and postural functions which supports the fact that it is main flexor of hip joint (dynamic function) and stabilizer of lumbar spine, sacroiliac and hip joins (postural function). Cranial part of psoas muscle has primarily postural role while caudal part of muscle has dynamic role.

fibre types ; human ; Immunohistochemistry ; myosin heavy chain ; origin ; psoas major muscle

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