[Body position of the human during hypokinesia and water-salt metabolism].

Two groups of 5 healthy volunteers each were exposed for 7 days to: 1) group 1 to horizontal bed rest and 2) group 2 to head-down tilt at -6 degrees. The purpose of the study was to determine the effect of body position on fluid-electrolyte metabolism and renal function. During the control period (14 days), bed rest and the recovery period the consumption of fluids and mineral substances and their renal excretion were measured. The typical changes in fluid-electrolyte metabolism during head-down tilt developed faster than during horizontal bed rest. The fluid-electrolyte balance became negative in the course of the exposure and returned to normal during the recovery period. The group 2 subjects showed greater body weight losses due to both fluid and muscle mass losses.