Clinical aspects of crew health

While the primary goal of the Apollo Program was to land men on the moon
and return them safely to Earth, there were other very important medical objectives.
The earlier Mercury and Gemini programs bad raised some concerns about the health
and safety of future crews. For example, the high metabolic energy expenditure of
extravehicular activity during the Gemini missions was unexpected. Before Apollo
astronauts could safely explore the lunar surface, reliable predictors of energy cost
and real-time monitoring techniques had to be developed. Physiological changes were
noted in individual crewmen, some more consistently than others. The most
important of these changes was in cardiopulmonary status demonstrated by
decreased exercise capacity, loss of red blood cell mass, and cardiovascular deconditioning demonstrated by a decrease in the effectiveness of antigravity cardiovascular responses during postflight stress testing.