Skeletal muscle is a very heterogeneous tissue that is composed of a large variety of functionally diverse fiber types. One of the unique features of skeletal muscle is its numerous fiber types and their distinct functional characteristics and compositions, which contribute to a variety of functional capabilities. These fiber types differ according to their molecular, metabolic, structural, and contractile properties, and thus, can be grouped according to various parameters, including myofibrillar protein isoforms, metabolic enzyme profiles, and structural and contractile properties. Therefore, the morphological and biochemical characteristics of muscle fiber types are major factors that influence energy metabolism within the skeletal muscles of live animals, as well as during the postmortem
conversion of muscle to meat. Skeletal muscle fibers are characterized by their precise organization of contractile and regulatory proteins into striatedmyofbrils, which result fromrepeating units arranged
in series, also known as sarcomeres. The ultra-structure and molecular composition of the sarcomere are remarkably similar among different muscle fiber types. However, underlying this apparent uniformity there is also a high degree of molecular variability, due to the existence of multiple isoforms of each myofibrillar component.