Abstract: The study involved 16 subjects: 8 in the control group, 4 in the group using the KORVIT (support unloading compensation) system, and 4 in the group using the Penguin suit (axial loading). The viscoelastic properties of muscles were studied using a MyotonPRO device. Based on the analysis of oscillation frequency, the device automatically calculates transverse muscle stiffness (N/m). Two passive countermeasures were applied from DI day 9: the KORVIT system and the Penguin suit. KORVIT involved 6 daily 20-minute sessions: 10 min of slow (75 steps/min) and 10 min of fast (120 steps/min) walking, with ≥40-min breaks. The Penguin suit was worn for ~4 hours/day (afternoon) with a 16–18 kg axial load. The aim of the work was to identify specific changes in the viscoelastic properties of lower leg muscles under countermeasures after 8 days of Dry Immersion. The viscoelastic properties of mm. tibialis anterior (TA) and soleus (SO) were assessed. Measurements were taken on day 8 of DI, on the day of DI accomplishment (R0), and on the 3rd day after the end of exposure (R+3). The effect of the DI in all groups was similar up to day 8. In TA, transverse stiffness decreased by an average of 12%, and in SO - by 7%. On day R0, stiffness in the TA in the control group was 15% lower than that before DI, while in the KORVIT and Penguin groups it was reduced by 8%. By R+3, in the control and Penguin group, stiffness remained reduced by 15 and 12%, consequently, while in the KORVIT group it returned to the baseline level. SO stiffness didn’t change in the course of the second week of DI in the control and Penguin group , while in the KORVIT group, it increased slightly on day R0 relative to day 8 of DI. By R+3, the stiffness in the control group remained reduced. In the KORVIT and Penguin groups, by R+3, a restoration of stiffness parameters was observed. The study confirmed that countermeasures in the form of mechanical stimulation of the soles support zones in locomotor regimen and axial loading, applied from day 9 of DI, had a positive effect on maintaining muscle stiffness, particularly in mm. tibialis anterior and soleus. This was manifested in a reduced decline in stiffness under DI conditions and accelerated recovery after the end of exposure. The study was supported by grant No. 24-15-00309, https://rscf.ru/en/project/24-15-00309/

Cite: Ponomarev I. , Gainutdinova E. , Kurbanova O. , Bekreneva M. , Rukavishnikov I. , Zelenskaya I. , Kitov V. , Shigueva T. , Tomilovskaya E.
Efficacy of passive countermeasures for minimizing adverse changes in muscle viscoelastic properties after one week of Dry Immersion
24th IAA Humans in Space Symposium, Montecatini, Italy, 20-24 April 2026 20-24 Apr 2026