[Mineral density of human skeletal bones in modeling of decreased gravity load]

Bone density in different skeletal compartments was measured in 9 healthy volunteers exposed for 370 days to head-down tilting (-5 degrees). Measurements were carried out using noninvasive techniques: quantitative computer tomography and dual photon absorptiometry (mono- and dichromatic). After bed rest no distinct mineral losses were seen in lumbar vertebrae, femoral diaphysis, tibial diaphysis, or forearm bones of most subjects. Mineral density of the femoral neck decreased in most subjects. The results are discussed with special emphasis on comparative values of the noninvasive methods, variations in the parameters under study during bed rest, and effectiveness of various countermeasures employed.