title: Acceleration tolerance at night with acute fatigue and stimulants.
abstract: 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.
authors: Human Effectiveness Directorate, Biosciences & Protection Division, Aircrew Protection Branch, Air Force Research Laboratory, Brooks City-Base, TX, USA. csramsey@juno.com
authors: Carol S
authors: CS
authors: Ramsey
authors: Paul M
authors: PM
authors: Werchan
authors: Wayne M
authors: WM
authors: Isdahl
authors: Joseph
authors: J
authors: Fischer
authors: John A
authors: JA
authors: Gibbons
mesh_terms: 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
chemical_list: D001559:Benzhydryl Compounds; D000697:Central Nervous System Stimulants; D008774:Methylphenidate; D010389:Pemoline; D000661:Amphetamine; D000077408:Modafinil