A.D. Kashtanov, R.V. Gallyamutdinov, E.V. Kustavinova, N.L. Kartashkina reviewed modern data on the topic of «Primary methods of adaptation of muscle fibers to physical activity and the ways of their implementation» on the basis of I.M. Sechenov First Moscow State Medical University (Sechenov University). Knowledge of the principles and mechanisms of adaptation of muscle fiber to the physical activity underlie professional sports and rational rehabilitation. Understanding the processes of muscle adaptation to stress, biochemistry, physiology and the genetic basis of this process is also necessary for the prevention of muscle tone and optimal condition of the musculoskeletal system and the cardiovascular system for people who are not involved in sports. Based on the received data it is important to recognize an orderly understanding of the laws of muscle adaptation. This review discusses ways to adapt muscle fibers to physical activity: compensatory and biochemical ones, as well as the mechanisms of these adaptive systems. Compensatory adaptation is based on a development in the non-contractile part of the muscle fiber (sarcoplasm), which leads to myofibrillar adaptation — the growth of myofibrils, which in turn promotes the increase of muscle strength and its ability to exercise. Biochemical adaptation is based on a change in the activity of enzymes and the number of their substrates in the muscle of an untrained person during his or her training. Increase in the activity of creatine phosphokinase and a decrease in the activity of lactic dehydrogenase in athletes is more pronounced, than in untrained people, which is associated with a greater fitness of the muscles for load, as more developed alternative ways to produce energy develop.