title: Acceleration endurance with pressure breathing during G with and without a counterpressure vest.
abstract: BACKGROUND
  The purpose of this study was to test whether pressure breathing during G (PBC) without a counterpressure vest negatively influences G endurance or increases breathing fatigue during extended duration high-G exposures.
  
  
  METHODS
  While using PBG, 10 subjects underwent 2 trials of +3 Gz exposures: once when wearing a counterpressure vest and once without. The exposures consisted of a relaxed, gradual G onset run until peripheral or central light loss, a straining rapid onset GC run to +6 Gz for 15 s, and a simulated aerial combat maneuver (SACM) G profile consisting of 10-s periods varying between +5 Gz and +9 Gz, during which subjects executed a hand-eye tracking task. The SACM endpoint was light loss or exhaustion. Subjects provided ratings of subjective effort and discomfort after the SACM.
  
  
  RESULTS
  Significant differences were found between the vest and no-vest conditions for only 3 of 19 measures: heart rate under G and two measures of tracking ability. The vast majority of data indicated no difference between the vest and no-vest conditions for performance under G.
  
  
  CONCLUSIONS
  This experiment supports previous studies and expands those previous results by increasing the duration of PBG exposure shown to not be influenced by wearing of the vest. We conclude that there is likely no practical advantage to wearing a counterpressure vest during PBG.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Walker
authors.forename: Todd
authors.initials: T
authors.lastname: Dart
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Morgan
authors.forename: Ulf I
authors.initials: UI
authors.lastname: Balldin
mesh_terms: D000054:Acceleration; D000328:Adult; D000337:Aerospace Medicine; D002498:Centrifugation; D005260:Female; D006112:Gravitation; D005676:Gravity Suits; D006339:Heart Rate; D006801:Humans; D018471:Hypergravity; D008297:Male; D010807:Physical Endurance; D011312:Pressure; D012119:Respiration; D055815:Young Adult