[Vascular mechanisms of adaptation to head-down tilt body posture].

Using occlusion plethysmography and rheography, the state of peripheral circulation of 18 test subjects during 25 exposures to head-down tilt was investigated. The test subjects were subdivided into two groups: nine subjects actively changed their body position by 90 degrees and nine others were passively transferred to the head-down position at an angle of -12 degrees. It was found that regular training facilitated the development of vascular mechanisms which assisted adaptation to the head-down tilt: it decreased the tone of resistance vessels of the arms and legs and that of capacitance vessels of the legs; it increased the tone of cerebral resistance and capacitance vessels.