[Impedancimetry of the hydration status and body composition of head-down tilted males]

Studies of the hydration status and body composition of 6 normal males was performed before and after 7-d head-down tilt (-8 degrees) with the use of a portable impedance-measuring device. Fluid sectors in the organism tended to proportionally reduce. By the end of the experiment, the total body fluid was found reduced by 6.4 = 0.9%; the intracellular and extracellular volumes fluids were reduced by 6.4 +/- 0.9% and 6.5 +/- 0.9 %, respectively. Body mass changed but little, and not to the same extent in each subject. Lean body mass measured with the device showed a small reduction (2.0 +/- 0.6 %), whereas the fatty body mass grew in all subjects by 14.0 +/- 3.1% on the average. These results lead to the conclusion that during the 7d head-down tilt the hydration status of the human body grew low concurrent with loss in muscular mass and increase in the body fatty mass.