Specific Features of the Motor Potentials of the Leg Muscles Induced by Magnetic Stimulation under the Conditions of a Five-Day “Dry” Immersion in Healthy Volunteers

The aim of this study was to analyze the mechanisms of the development of hypogravitational hyperreflexia in the motoneuron pool of gravity-dependent muscles such as the gastrocnemius and soleus muscles of the leg under the conditions of five-day “dry” immersion in healthy volunteers using the method of transcranial and trans-spinal magnetic stimulation. The essence of the method lies in the stimulation of the areas of interest (motor areas of the cerebral cortex and lumbosacral thickening) with an electromagnetic stimulus. The study involved 10 subjects at the age of 29.9 ± 6.9 years, with no history of movement disorders or neurological diseases. The excitability of the motor neuron pool in both muscles was judged by the values of the thresholds and amplitudes of the motor response caused by transcranial and trans-spinal magnetic stimulations. A general pattern manifested in a significant decrease in thresholds and an increase in the amplitudes of motor responses caused by trans-spinal magnetic stimulation in both muscles gas been discovered. Specifically, the threshold of spinal evoked motor responses in both muscles decreased by 20%, and the amplitude increased by 150% after the end of immersion. The data obtained during the experiment confirm the spinal nature of the origin of hypogravitational hyperreflexia.