Реферат: The aim of the work was to study the effects of short (from several hours to several days) and long (two-week) supportlessness on spinal reflex responses in human leg extensor muscles. The study was carried out within the framework of a project whose task is to determine the leading factor (support or proprioceptive unloading) in the development of changes observed in the chronic phase of adaptation to Dry Immersion, in individual segments and at different levels of the organization of the human sensorimotor system. The solution of this problem requires a comprehensive study of the motor control system during three different experimental exposure conditions (two-week exposure to support withdrawal without countermeasures – 2024-2025; two-week exposure to support withdrawal with compensation of support unloading starting from the second week of exposure– in the plan for 2025-2026; two-week exposure to support withdrawal with compensation of axial weight unloading starting from the second week of exposure – in the plan for 2027). Changes in the processes of spinal mechanisms were assessed in 4 participants (27.8±2.9 years old, height 179±4 cm, weight 73.95±3.68 kg) of the two-week Dry Immersion (DI). As indicators reflecting the state of the motor neuron pools of the spinal cord, the characteristics of the H-reflex of the shin muscles were studied during the experiment. The state of excitatory and inhibitory spinal mechanisms was determined by the thresholds and maximum amplitudes of the recruitment curve of the H-reflex of the shin muscles (mm. soleus and gastrocnemius) before the start of DI, after 5 hours of exposure, on the 3rd, 5th, 7th, 9th, 11th, 13th, 15th days of DI, as well as on the 2nd and 5th days after its accomplishment. The study demonstrated a decrease in the thresholds of the H-reflex in the soleus muscle after 5 hours of DI, with a maximum decrease on day 3. The thresholds remained below the initial values throughout DI, returning to the initial values 2-5 days after its completion. The amplitude of the H-reflex increased by the 5th day of DI, remaining above the initial values until the DI completion. Preliminary results of this study showed that both 7-day and 14-day support unloading are accompanied by the development of changes in the system of spinal reflexes with the opposite dynamics of the acute and chronic phases. These observations allow to suggest the development of compensatory processes in spinal reflex system after 3-5 days of exposure. The study was supported by the Russian Science Foundation grant No. 24-15-00309, https://rscf.ru/en/project/24-15-00309/

Библиографическая ссылка: Shigueva T. , Abu Sheli N. , Urbanskaya A. , Kitov V. , Rukavishnikov I. , Tomilovskaya E.
Acute and chronic phase of adaptation to supportlessness (during two- week Dry Immersion) in the system of spinal reflexes
44 Annual the International Society of Gravitational Physiology Meeting (ISGP), Sapporo, 2025 18-23 May 2025