In vivo bone mineral studies on volunteers during a 370-day antiorthostatic hypokinesia test.

Bone mineral of spine, femur, tibia, forearm, calcaneus, hand, and foot was studied on nine volunteers by quantitative computed tomography, neutron activation analysis, single and dual photon absorptiometry during and after long-term hypokinesia. Conditions of long-term space flight were simulated using a 370-day antiorthostatic hypokinesia test. It is shown that the highest mineral losses occur in foot bones including calcaneus. Remedial measures undertaken delay the process of osteoporosis development but do not completely exclude it. The results obtained by different methods are often conflicting. Consequently, the accuracy of the in vivo methods for bone mineral determination must be more thoroughly studied.