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Human skeletal muscle fiber types: delineation, development, and distribution
1Department of Biological Sciences, College of Osteopathic Medicine, Ohio University, Athens 45701, USA.
Summary
Human skeletal muscle fiber types are classified by myofibrillar adenosine triphosphatase (mATPase) and myosin heavy chain (MHC) content. Fiber type distribution varies within and between individuals, influenced by activity and hormones throughout life.
Area of Science:
- Muscle Physiology
- Histochemistry
- Human Anatomy
Background:
- Human skeletal muscle comprises diverse fiber types.
- Classification is crucial for understanding muscle function and adaptation.
- Previous research has focused on identifying and characterizing these fibers.
Purpose of the Study:
- To review studies on the classification, development, and distribution of human skeletal muscle fiber types.
- To correlate histochemical mATPase-based typing with molecular MHC profiles.
- To discuss the adaptability and variability of muscle fiber types.
Main Methods:
- Histochemical analysis of myofibrillar adenosine triphosphatase (mATPase) stability/lability.
- Assessment of myosin heavy chain (MHC) content and isoforms.
- Review of existing literature on human skeletal muscle fiber typing.
Main Results:
- Seven distinct human skeletal muscle fiber types identified via mATPase.
- Strong correlation between mATPase-based fiber types and specific MHC profiles.
- Muscle fibers exhibit adaptability, with transient types and lifelong alterations.
Conclusions:
- mATPase and MHC analysis provide a robust framework for human skeletal muscle fiber classification.
- Significant individual and intra-muscle variation in fiber type distribution complicates data interpretation.
- Activity levels and hormonal factors influence muscle fiber type dynamics throughout life.