Physiological Findings
Few serious biological effects were noted during the early years of space flight. Even the 21-day quarantine of astronauts returning from the Apollo moon mission was , because no infectious agents were . The body that were (often with specially miniature instruments) included heart rate, pulse, body temperature, blood pressure, respiration, speech and alertness, and brain waves. Few changes . Changes in hormones and in of salts in the blood did take place, but these were not detrimental. Eating in weightlessness was accomplished by packaging food in containers that could be squeezed directly into the mouth, and special systems were for collection of fluid and solid wastes. The lack of a natural time in space was for by keeping the astronauts' synchronised with earth time.

changes were because of the close confinement of a few in a small space with limited activity. Few problems were noted, however, perhaps because the astronauts were chosen for their emotional and high , and because they were enough to keep them almost busy. Irradiation was also found to have little effect. Short orbital flights produced about equal to one X-ray - about the same as suborbital flight. The crew on the longer Skylab flight many times this dose. Space flights are planned to avoid when solar flares are expected to , as these can emit dangerous levels of gamma radiation.

However, although it was that gravity is necessary for growth, the magnitude of physiological changes by extended in a microgravity came as something of a surprise. Serious problems, including loss of bone matter and muscle strength, were observed to result from long-term weightlessness, as during the 237-day mission of three cosmonauts aboard a Salyut space station in 1984. Moreover, atrophy of certain muscles, particularly those of the heart, was seen to be especially dangerous because of its effect on the of the entire cardiovascular system. The blood itself was found to be , with a measurable decrease in the number of oxygen-carrying red blood cells.

On a seven-day Space Shuttle mission in 1985, these effects were studied in an experiment using 24 rats and 2 monkeys. Post-flight examination not only the expected loss of bone and muscle strength but a decrease in of growth hormone as well.

These findings are taken into consideration now whenever plans are made for crewed space flight. The busy work of astronauts in space are to include regular exercise , muscle tone. And plans for the operation of permanently crewed space stations now include provisions for changing crews on a regular basis, so as not to subject astronauts to weightlessness for of time.