Human amino acid excretion during and following an extended airborne alert.

The urinary excretion of free amino acids was measured in 15 men who participated in a continuous airborne alert for an extended period of time. These men made up one of three teams which took turns so as to assure that at least one team remained airborne in an EC-135J aircraft at all times during the 96-h alert. The team making up the test group herein reported was airborne for 8.5 h on each of four successive days; flights were flown during the daytime. The data strongly suggest that the participants experienced anticipatory stress during the early part of the first two flight days of the alert, after which the excretion of amino acids was virtually unaltered. Additionally, amino acid excretion during the 24-h period following the alert was essentially in accord with baseline values established for another groups of subjects.