Аннотация:Studies of muscle tone in space medicine began to be carried out in the first space flights (SF) with human participation. In these studies, a decrease in the tone of the skeletal muscles of the lower extremities was shown by visual inspection and palpation (Kakurin, 1971, Cherepakhin, 1970). More recent comparative experiments by Kozlovskaya et al. (1984) using quantitative assessment methods, revealed a significant change in muscle tone and characteristics of spinal reflexes after completion of SF and in models of Dry Immersion (DI) and head down bed rest (HDBR). In this study, the comparability of the detected changes after DI and HDBR of the same duration was shown. A study of the electrical activity of the leg muscles during the transition to zero gravity showed an instantaneous EMG “silence” (Kawano, 2004). However, at the turn of the century, interest in the study of muscle tone declined, probably partly due to the lack of a standard adequate technique and increased attention to the speed-strength characteristics of the skeletal muscles of astronauts. In recent years, thanks to the development of standardized equipment, studies of muscle tone have been continued both in ground-based experiments (Treffel, 2016, Rukavishnikov, 2017), in parabolic flight (Schneider, 2015) and at the International Space Station. In this paper, we summarize our research obtained in DI conditions and the data of other researchers in this area. We also would outline some of the ways in which research on muscle tone can be developed. A comprehensive analysis of data over 5 years of research shows that placement of subjects in DI conditions causes a sharp drop of tone in the postural and locomotor muscles. The strongest decrease in the tone of gravity-dependent muscles occurs in the first 2-6 hours of immersion exposure. A long-term downward trend over 21 days of DI was recorded in the muscles of the anterior surface of the thigh and shin, as well as the Achilles tendon. The authors remember and honor the contribution of Inessa Benediktovna Kozlovskaya, prof., member of RAS in the study of muscle tone. This work was supported by the Russian Academy of Sciences 63.1.
