At least 2 months before flight, each subject performed 2 or 3 PSL LBNP protocols. In the 4 months before flight, each crew member performed 2 or 3 ramp protocols. The postflight LBNP ramp test was done within 4 to 6 hours of landing (R+0), and at 3 other times between R+1 and R+8.
Before flight, all crew members completed the LBNP ramp test. On day R+0, 5 of 10 were unable to complete the test due to presyncopal symptoms; HR remained elevated during all recovery tests. TPR was greater after landing than before flight. Blood analysis on R+0 revealed slight hemoconcentration and augmented catecholamine levels. Catecholamine levels were also increased by LBNP between R+1 and R+8. Leg circumference decreased dramatically after space flight and the decrease persisted for 6 to 8 days after landing. This may represent an acute decrease in muscle mass, not due solely due to dehydration because blood results indicated rapid recovery of body fluids within 48 hours. In comparing postflight response to LBNP and the stand test, LBNP gave no evidence of depressed orthostatic peripheral vascular response, which may be due to the difference between these two types of orthostatic stressors.
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