The "Angiogenic Switch" and Functional Resources in Cyclic Sports Athletes

Regular physical activity in cyclic sports can influence the so-called "angiogenic switch", which is considered as an imbalance between proangiogenic and anti-angiogenic molecules. Disruption of the synthesis of angiogenic molecules can be caused by local changes in tissues under the influence of excessive physical exertion and its consequences, such as chronic oxidative stress and associated hypoxia, metabolic acidosis, sports injuries, etc. A review of publications on signaling pathways that activate and inhibit angiogenesis in skeletal muscles, myocardium, lung, and nervous tissue under the influence of intense physical activity in cyclic sports. Materials: We searched PubMed, SCOPUS, Web of Science, Google Scholar, Clinical keys, and e-LIBRARY databases for full-text articles published from 2000 to 2020, using keywords and their combinations. Results: An important aspect of adaptation to training loads in cyclic sports is an increase in the number of capillaries in muscle fibers, which improves the metabolism of skeletal muscles and myocardium, as well as nervous and lung tissue. Recent studies have shown that myocardial endothelial cells not only respond to hemodynamic forces and paracrine signals from neighboring cells, but also take an active part in heart remodeling processes, stimulating the growth and contractility of cardiomyocytes or the production of extracellular matrix proteins in myofibroblasts. As myocardial vascularization plays a central role in the transition from adaptive heart hypertrophy to heart failure, further study of the signaling mechanisms involved in the regulation of angiogenesis in the myocardium is important in sports practice. The study of the "angiogenic switch" problem in the cerebrovascular and cardiovascular systems allows us to claim that the formation of new vessels is mediated by a complex interaction of all growth factors. Although the lungs are one of the limiting systems of the body in cyclic sports, their response to high-intensity loads and other environmental stresses is often overlooked. Airway epithelial cells are the predominant source of several growth factors throughout lung organogenesis and appear to be critical for normal alveolarization, rapid alveolar proliferation, and normal vascular development. There are many controversial questions about the role of growth factors in the physiology and pathology of the lungs. The presented review has demonstrated that when doing sports, it is necessary to give a careful consideration to the possible positive and negative effects of growth factors on muscles, myocardium, lung tissue, and brain. Primarily, the "angiogenic switch" is important in aerobic sports (long distance running). Conclusions: Angiogenesis is a physiological process of the formation of new blood capillaries, which play an important role in the functioning of skeletal muscles, myocardium, lung, and nervous tissue in athletes. Violation of the "angiogenic switch" as a balance between proangiogenic and anti-angiogenic molecules can lead to a decrease in the functional resources of the nervous, musculoskeletal, cardiovascular, and respiratory systems in athletes and, as a consequence, to a decrease in sports performance.