ИСТИНА

Having set a goal to study the dynamics of biomechanical and electromyographic parameters while cosmonauts perfom locomotions on treadmill during long space flights (SF), we proceed from the basic concept that motor disorders occupy an important place in the complex of disorders caused by microgravity, which are accompanied by a number of changes in the state of both the muscle periphery and the leading sensory inputs - supporting, muscular, vestibular (A. I. Grigoriev, 2004; I. B. Kozlovskaya, 1990, 2002, 2007). The study was conducted in the framework of the onboard experiment "MOTOKARD". Locomotor test were performed by 13 cosmonauts aged 50.1 ± 7.4 yr and weight 89.3 ± 7.1 kg on board of the Russian Segment of International Space Station on a monthly basis during SF, two sessions were performed of the experiment before and two sessions - after SF. The duration of flight consisted from 5 to 6 months. The ground reaction forces (GRF) while walking were recorded by 190-197 pressure sensors inbuilt in measuring insoles under the feet of cosmonauts during walking with the recommended speed 1.24-2.48 mph in active modes of the treadmill track. In active mode the track is driven by the electric drive. Also, the electromyogram was recorded from 4 muscles: mm. anterior tibialis, soleus, gastrocnemius and quadriceps femoris. During the first month of SF, GRF values of the toe o˙ phase increased by 11.67 ± 2.34 % (p < 0.05). At the same time, GRF values of the heel strike phase decreased, reaching a significant di˙erence with baseline values in the second month of SF: namely, 9.36 ± 1.25 % (p < 0.05). This led to changes in the interrelationship of the heel strike to toe o˙ phases: before SF - the peak GRF values were registered in the heel strike phase, while during SF and on the 8th day after landing the peak GRF values were registered in the toe o˙ phase. In the toe o˙ phase, 2 muscles are actively involved: m. soleus and m. gastrocnemius (M. L. Latash, V.M. Zatsiorsky, 2015). The ratio of the amplitude of EMG burst of m. soleus to the amplitude of EMG burst of m. gastrocnemius before SF was 1,12 ± 0.36, in the first month of SF - 1,64 ± 0.58 (p < 0.05), in the 2nd month of SF - 1,43 ± 0.29, in the 3rd month of SF - 1,29 ± 0.36, in the 4th month of SF - 1,1 ± 0.42 and after SF - 1,08 ± 0.28. From the results obtained, it can be concluded that in the first three months of space flight, the soleus muscle activity the promotes greater to the establishment of the cosmonaut’s new walking strategy. The study us supported by Roscosmos.