Acceleration tolerance at night with acute fatigue and stimulants.
BACKGROUND
The impact of pharmacological agents on aviators concerns all flight surgeons. This study tested the related hypotheses that acute fatigue reduces +Gz tolerance and endurance, and that stimulants can partially reverse this impact. Additionally, the researchers attempted to develop a test battery sensitive enough to detect subtle differences in aviator cognition and performance among conditions.


METHODS
To determine the effect of fatigue on +Gz tolerance and the impact of stimulant use, 10 male centrifuge subjects, mean age 32, from Brooks City-Base, TX, were tested in a repeated measures study under five nighttime conditions following an average of 22 h of sustained wakefulness during their circadian nadir. Using a within-subject design, subjects received placebo, dextroamphetamine 10 mg, modafinil 200 mg, methylphenidate 10 mg, and pemoline 37.5 mg at night, and were tested during a daytime control session. Cognitive/performance tests were administered before each centrifuge run.


RESULTS
No difference in +Gz tolerance or endurance was detected among conditions. The cognitive/performance tests also did not detect any differences. Subject perception that anti-G straining maneuver (AGSM) difficulty was greater during the night placebo condition than during the daytime control, methylphenidate and modafinil night conditions reached statistical significance (P = 0.005, 0.012, 0.022, respectively).


CONCLUSIONS
Physiological changes during the circadian nadir following acute sleep deprivation do not appear to negatively impact +Gz tolerance. A standardized protocol sufficiently sensitive to detect subtle behavioral and performance effects would be useful to test and compare the effect of other pharmacological agents on aviators.
Ramsey
Carol S
CS
Human Effectiveness Directorate, Biosciences & Protection Division, Aircrew Protection Branch, Air Force Research Laboratory, Brooks City-Base, TX, USA. csramsey@juno.com
Werchan
Paul M
PM
Isdahl
Wayne M
WM
Fischer
Joseph
J
Gibbons
John A
JA
D000054:Acceleration; D000222:Adaptation, Physiological / Q000187:drug effects / Q000502:physiology*; D000328:Adult; D000337:Aerospace Medicine; D000661:Amphetamine / Q000494:pharmacology; D000704:Analysis of Variance; D001559:Benzhydryl Compounds / Q000494:pharmacology; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D003071:Cognition; D005221:Fatigue / Q000188:drug therapy / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008774:Methylphenidate / Q000494:pharmacology; D000077408:Modafinil; D010389:Pemoline / Q000494:pharmacology; D010807:Physical Endurance / Q000187:drug effects / Q000502:physiology*; D012892:Sleep Deprivation / Q000188:drug therapy / Q000503:physiopathology
D001559:Benzhydryl Compounds; D000697:Central Nervous System Stimulants; D008774:Methylphenidate; D010389:Pemoline; D000661:Amphetamine; D000077408:Modafinil