[Strength and mineral composition of human vertebrae during prolonged bed rest]

Reduction of the strength of vertebrae not associated with osteoporosis has been revealed in patients who underwent strict bed rest for 20-40 days and died from sudden complications. The strength of vertebrae of humans who died in an accident was assumed as normal. A comprehensive analysis has shown that reduction of the strength was caused by alterations in the chemical composition of vertebral mineral substances, particularly by the diminution of the calcium content.