Athletic endurance training - advantage for space flight?: The significance of physical fitness for selection and training of spacelab crews.

While intensive physical exercise has been part of the conditioning of astronauts and consmonauts for spaceflights, its benefits have been questioned. After reviewing the pertinent literature, it is concluded that the morphological and functional changes obtained with athletic endurance training are rather specific and of no general advantage for the tolerance to space stresses. Particularly during gravitational loads, in the relaxed subject, these changes allow a more pronounced shift of fluid into the lower extremities, with the possible consequence of a reduced tolerance. This unfavourable response, obviously, is accentuated through immersion and weightlessness. The aerobic work capacity is also more impaired in athletes. Based on these conclusions, recommendations for crews and passengers of future Spacelab missions are given with respect to selection and pre-and in-flight physical exercise.