[Study of the phase structure of the cardiac cycle during the test with decompression of the lower part of the body in long-term (140-185 days) space flights].

Before and during prolonged space flights changes of systolic time intervals in response to LBNP tests were qualitatively similar and corresponded to the syndrome of myocardial hypodynamics due to insufficient venous return. However, the level of the changes and their contribution to the cardiac cycle were different in flight and on the ground. Greater changes in systolic time intervals seen in flight may be attributed to larger blood shifts to the abdomen and legs.