Acta Astronautica 59 (2006) 13 – 19 www.elsevier.com/locate/actaastro New approaches to countermeasures of the negative effects of microgravity in long-term space flights I.B. Kozlovskaya ∗ , I.V. Sayenko, O.L. Vinogradova, T.F. Miller, D.R. Khusnutdinova, K.A. Melnik, E.N.Yarmanova Russian Federation State Research Center, Institute for Biomedical Problems of the Russian Academy of Sciences, 76A Khoroshevskoe sh., Moscow, 123007 Russia Abstract The results of studies of the effects of mechanostimulation of the soles’ support zones on the effects of microgravity in the motor system are presented. It was shown that mechanostimulation of the soles support zones in regimen of slow and fast walking, being used daily during 7 days dry immersion, eliminates fully or suppress considerably all the microgravity effects. In subjects in which stimulation was applied six times a day by 20 min every hour the decrease of force–velocities properties and atrophic changes in the leg extensors after the exposure to microgravity were not revealed. Their transverse stiffness was only slightly lowered and the amplitude of electromyographic activity at rest stayed unchanged. The level of orthostatic deficiency in this group was also lower than in the group without stimulation. Thus presented experimental results in full agreement with previous studies allow to conclude that support afferentation plays the leading role in gravitational deprivation of the activity of tonic muscle system and that adequate mechanostimulation of the soles support zones can be used as a countermeasures mean in weightlessness. © 2006 Elsevier Ltd. All rights reserved. 1. Introduction The countermeasures for long-duration space flights are aimed at maintaining physical health and perfor- mance of crewmembers high enough to enable them to accomplish mission programs and to return safely to Earth. However, application of these countermeasures, especially physical exercises (PhE), at appropriate in- tensity and volume is not an easy task that is used by most of the cosmonauts as a ready-made excuse for de- viation from the prescribed modes [1]. The analysis of data on countermeasures use dur- ing flight (Fig. 1) has revealed that out of 12 members ∗ Corresponding author. Tel.: +7095 195 6837; fax: +7095 195 2253. E-mail address: ikozlovs@mail.ru (I.B. Kozlovskaya). 0094-5765/$ - see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.actaastro.2006.02.045 of Russian crews on ISS station only one performed the PhE in full accordance with the exercise program. Postflight changes in almost all physiological systems in this cosmonaut were negligible. Regimens used by four more cosmonauts were close to the recommended level. The changes in structure and functions in muscles, bones, systems of motor control (posture, locomotion, eye–head coordination etc.) in this case were in the range of the mean for the group of cosmonauts flown on “Mir” station. At the same time in three cosmonauts the volumes and intensities of PhE performed on board were significantly lower than the recommended ones. Accordingly, the negative effects in physiological sys- tems were in this case very deep. The same variability of level of PhE in flight and values of physiological changes recorded postflight was revealed in cosmonauts flown on “Mir” station [2] and as in flight on ISS these