The Variability of DNA Structure and Muscle-Fiber Composition

—Competitive success in sports, as well as a predisposition to some chronic pathologies, depends to a certain degree on the composition of muscle fibers. The proportional variability in muscle fibers (slow fibers ranging from 5 to 90%) among people depends on their genotypes and environmental factors. The contribution of hereditary factors to the development of muscle fibers ranges from 40 to 50%. This review describes contemporary approaches to the associations between DNA polymorphisms and the muscle fiber composition. Seven DNA polymorphisms associated with the proportional variability in skeletal muscle fiber types that were also shown to have an association with a predisposition to athletic activities and some diseases, such as obesity, type II diabetes, and hypertension, have been detected thus far. These seven markers are localized in the genes that are responsible for the contractile characteristics of skeletal muscles, lipid and carbohydrate metabolism, vascular tonus, and adaptation to hypoxia. Studies based on the whole-genome and epigenomic technologies are now underway to solve the problem of genetic determination of muscle fibers. The results of the study will permit the development of noninvasive methods for determining the composition of human muscle fibers and improving the efficiency of athletic training.