The effect of exercise on blood flow in long-term missions
On long flights during the tests with DFN identified natural features of the response of the cardiovascular system, which as a whole the entire group of astronauts orbital stations Salyut-6 and Salyut-7″ manifested as follows.
After work, average power compared to the rest the degree of increase in EE was, as a rule, considerably less than before the flight. Some astronauts on a separate flight stages its value even after the load decreased. Was significantly decreased relative increase of the IOC (it
was 54-58%). Naturally lower than before the flight, decreased Upsf (29-31%).
After performing the 2nd step load in 5 out of 10 cases of EE were decreased in comparison with the value before the test. However, the decrease of EE was reduced IOC in relation to 1 minutes rest because statistically there was an increase in heart rate, which was 74% vs. 47% after 1st stage.
In flight after the load (in comparison with pre-flight data obtained in the similar periods of the sample) recorded a statistically significant decrease hemicircular (PP 12-16%, IOC 9-13%). UPSF/d had only a tendency to decrease, especially after the 2nd stage. When performing a two-stage sample of EE on 1-th minute of the recovery period (after the 2nd load) was 11% less than 1 minutes of rest (after the 1st load).
Noted above some level of functional state of cardiovascular system in microgravity suggests that the excess volume of blood in the cardiopulmonary region, and the increase during exercise pulmonary component of this volume contributes to the early period of restitution greater than on Earth, the displacement of the blood vessels in the underlying areas. This assumption seems all the more justified, considering the possible in zero gravity, the existence of a free stretch and increase the elasticity of the veins of the leg due to decreased transmural pressure.
One reason for the decrease in EE of the heart after exercise (or reduction reaction) can be altered vascular tone [Michel E. L. et al.]. In addition, after the load is the deposition of blood in the arterioles have just worked the muscles of the lower limbs, in weightlessness — as a result of reducing the role of peripheral muscular “hearts” in the movement of blood to the heart.
Apparently, the combined impact of these factors leads immediately after the cessation of work to the deposition of blood in the lower parts of the body, reduction of venous flow to the cavities of the heart, reduced end-diastolic volume of the left ventricle and as a consequence identified in our studies, the practical lack of increase in EE or even decrease with increasing intensity of work.
Our results are in full accordance with the data of echocardiographic studies (see O. Yu. Atkov et al. in this monograph) on the restructuring phase patterns diastole in long-term space flights, observed V. I. Alferova.
In weightlessness after the load of various capacities (750-1050 mg/min) increase in IOC are always secured under the dominant influence of chronotropic function of the heart by enhancing sympathetic adrenergic stimulation, the most manifested with increased load, i.e. the change of the mechanism of formation of the IOC in response to physical work.
Summarizing the research . towards the study of Central and regional circulation of man in short-term and long-term space flights, it should be noted that the observed changes in the terms of peace manifested primarily by a redistribution of the pulse blood and tone the regional vessels (head, forearms, shins) with little overall deviation from preflight values of EE of the heart and the IOC. Marked change of response to functional load tests in the form of exposure ODNT and DPN on a Bicycle Ergometer.
During the tests with DPN on the 1st minute period of restitution decreased role of EE heart in the formation of the IOC with increasing chronotropic function of the heart. The sample with the application ODNT in long-term flights had a normalizing effect on the tone of the small vessels of the brain, which in turn confirmed the reversible nature of the vascular responses in flight conditions. Identified during the flights, the changes were due to restructuring of the overall hemodynamic status of the human body in weightlessness and to some extent depended on the duration of the flight and the location of the vascular area relative to the heart. These changes reflect the process of adaptation to the space flight environment and pointed to the preservation of the compensatory capacity of the cardiovascular system in flights lasting up to 237 days.
The obtained data was complemented with previously accumulated information about the effect of weightlessness on the cardiovascular system. Along with this they are allowed to put the specialists in space medicine new tasks, which require the continuation of studies on the phenomenology and to clarify the mechanisms of hemodynamic changes caused by the influence not only of weightlessness and other space flight factors.