Metabolic Regulation and Muscle Function in Health Disease

Skeletal muscle plays a vital role in our ability to move and breathe, accounting for approximately 50% of our body mass. It is connected to bones through tendons, facilitating bodily movement (Birbrair et al., 2014). Composed of long, multinucleated muscle fibers held together by interstitial connective tissues, skeletal muscle forms a syncytium known as a myofiber during development, resulting from the fusion of myoblasts, individual muscle precursors. These myofibers are bundled together and contain myofibrils, which are filaments consisting of the contractile proteins myosin and actin (Fig. 1). The interaction between thick myosin filaments and thin actin filaments allows for the contraction and relaxation of skeletal muscle. The arrangement of these filaments creates a pattern of dark and light bands, giving the muscle a striated appearance (Irving, 2017).

The classification of skeletal muscle fibers is based on their contraction speed, enzymatic velocity, and metabolic profile. Three types of muscle fibers can be found in skeletal muscle, and their proportions may vary depending on the muscle's functional role. These fiber types include slow oxidative fibers (Type I fibers), fast oxidative glycolytic fibers (Type IIa fibers), and fast glycolytic fibers (Type IIB fibers) (Pette & Staron, 2000). The connective tissue surrounding the muscle fibers is essential for muscle function as well. It not only serves as tendons, attaching the skeletal muscle to bones but also houses an abundant supply of blood vessels and nerves that communicate with the muscle.