Human amino acid excretion patterns during and following prolonged multistressor tests

As a feasibility study, two men were tested in a series of simulated flights which comprised a factorial experiment. Plysiologic data were collected during a 2-d baseline period, four 36-h experimental periods, and four recovery periods. The experimental conditions were as follows: a) uncomplicated simulated flight, b) flight complicated by extreme environmental dryness, c) flight complicated by mild hypoxia, and d) flight complicated by both dryness and -ypoxia. Throughout each flight the subjects alternately worked 2 h and rested 2 h, performing on psychomotor measuring devices during each work period. Five other men were studied under baseline conditions and during a 48-h simulated flight complicated by hypoxia. Urinary nitrogenous metabolites, including individual amino acids, were examined for sensitivity to the stressor complexes. Certain of the amino acids had high stressor sensitivity, tending to differentiate the effects of the single, double, and triple stressor complexes. They also differentiated the physiologic states in the experimental and recovery periods.