[Mechanical stimulation of soles' support zones: non-invasive method of activation of generators of stepping movements in man].

The effects of mechanical stimulation of the soles' support zones in regimens of slow and fastwalking (75 and 120 steps per minute) were studied using the model of supportlessness (legs suspension). 20 healthy subjects participated in the study. EMG activity of hip and shin muscles was recorded. Kinematic of leg movements was assessed with the use of videoanalysis system. Support stimulation was followed by leg movements in 80% of cases, in 53% it was a locomotion-like movement. EMG bursts accompanied the movements. Involvement order and alteration of bursts in muscles were similar to voluntary walking. EMG activity occurred with a delay of 5.17 ± 1.08 seconds for hip muscles and 14.01 ± 2.82 seconds for shin muscles, frequency of bursts differed from stimulation frequency. Support stimulation was followed by leg movements in 80% of cases, in 53% of which they had characteristics of locomotions being accompanied by the burst-like electromyographic activities. Involvement order of the leg muscles and organization of antagonistic muscles activities were analogous to that of voluntary walking. The latencies of electromyographic activity in hip muscles composed 5.17 ± 1.083 s and 14.01 ± 2.82 s - for shin muscles, frequency of bursts differed significantly from stimulation frequency. In 31% of cases the electromyographical activity following the stimulation of the soles' support zones was not burst-like. Its amplitude rose smoothly reaching a certain level that was subsequently maintained. Results of the study showed that soles' support zones stimulation in regimen of locomotion can activate a locomotor generator and that effect evoked by this stimulation includes not only rhythmical but also non-rhythmical (probably postural) components of walking.

[Characteristics of negative pressure inspiration effect on the cardiorespiratory system of humans in the conditions of 5-day dry immersion].

Changes in external respiration and central hemodynamics induced by negative (relative to atmospheric) inspiration pressure were studied in supine subjects before and on day-4 of a dry immersion (DI) experiment. Changes in the cardiorespiratory system as a result of negative inspiration pressure included rise of the amplitude of breathing motions and reduction of their frequency, and distinct breathing-related HR fluctuations. Combination of immersion and altered pressure in the mask caused breathing-related variations of systolic pressure and plethysmogram signal, and improved arterial blood oxygenation. These results can be useful for developing pressure-gradient methods of counteracting the adverse effects of blood redistribution toward the cranial-end.