[Evaluation of the changes in the bone structures of the human axial skeleton in prolonged space flight].

Changes in the mineral content of the left heel bone of the Salyut-6 crewmembers who made 75--184-day flights were measured by direct photon absorptiometry. The postflight results were compared with the predicted rate of bone atrophy. This parameter was derived from the data concerning variations in the mineral content of spongy bones of men and animals exposed to actual and simulated weightlessness for various time intervals. The efficiency of countermeasures against the adverse effect of weightlessness on bones was assessed. It is concluded that crewmembers with a high content of minerals in spongy structures of the axial skeleton and a low basal metabolism should be selected for prolonged space missions.