Describing the experience of his space exploration Russian astronaut Georgi Grechko said:
"You feel as if you are hanging head downward. The blood rushes to your head. It swells and you get red in the face. Your chest becomes overfilled with blood. In addition, you lose coordination."
Another Russian astronaut Valeri Ryumin had the same sensation:
"At the end of the day you no longer recognize your swollen face in the mirror. You are unable to coordinate your movements. You are constantly bumping into something mostly with your head."
Experience in space flights has shown that in approximately 75 percent of the instances the astronauts acutely feel the effect of weightlessness on their body. Astronauts feel as if they have been turned upside down, they suffer from dizziness, they cannot coordinate their movements and lose their appetite. Naturally this state negatively affects their capacity for work.
Doctors call this condition "space sickness". This is not really a sickness, but man's response to the absence of the force of gravitation and disruptions in normal blood circulation.
During this stage of space flight the sensations of every astronaut are individual. Some become adjusted to weightlessness faster, others slower. In general, however, the unpleasant feelings disappear in seven to ten days. As the sojourne in space grows longer the process of redistribution of blood in the body becomes stabilized.
Some astronauts say that during subsequent flights the process of adaptation to weightlessness is much less painful and shorter. It appears that the body "remembers" this state and this makes it easier for the astronaut to become adjusted to the absence of the force of gravity.