title: Exercise performance of sea-level residents at 4300 m after 6 days at 2200 m.
abstract: Partial acclimatization resulting from staging at moderate altitude reduces acute mountain sickness during rapid exposure to higher altitudes (e.g., 4300 m). Whether staging also benefits endurance performance has not yet been scientifically evaluated.
  
  
  OBJECTIVE
  Determine the effectiveness of staging at 2200 m on time trial (TT) performance of unacclimatized sea-level residents (SLR) during rapid exposure to 4300 m. There were 10 healthy men (mean +/- SE: 21 +/- 1 yrs) who performed 720 kJ cycle TT at SL and following -2 h of exposure to 4300 m (459 Torr) before (ALT-1) and after (ALT-2) living for 6 d at 2200 m (601 Torr).
  
  
  METHODS
  Hemoglobin concentration ([Hb]), hematocrit (Hct), arterial oxygen saturation (SaO2), ratings of perceived exertion (RPE), and heart rate (HR) were measured before and during exercise.
  
  
  RESULTS
  Compared to SL (73 +/- 6 min), TT performance was impaired (P < 0.01) by 38.1 +/- 6 min at ALT-1, but only by 18.7 +/- 3 min at ALT-2. The 44 +/- 8% TT improvement at 4300 m was directly correlated with increases in exercise SaO2 (R = 0.88, P < 0.03), but not to changes in [Hb] or Hct. In addition, RPE was lower (13 +/- 1 vs.16 +/- 1, P < 0.01) and HR remained at approximately 148 +/- 5 bpm despite performing the TT at a higher power output during ALT-2 than ALT-1 (120 +/- 7 vs.100 +/- 10 W, P < 0.01).
  
  
  CONCLUSIONS
  Partial acclimatization resulting from staging attenuated the impairment in TT performance of SLR rapidly exposed to 4300 m. The close association between improved TT performance and changes in exercise SaO2, compared to a lack of association with changes in [Hb] or Hct, suggest ventilatory acclimatization may have been the major factor contributing to the performance improvement.
authors.affiliation: Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760-5007, USA. Charles.Fulco@us.army.mil
authors.forename: Charles S
authors.initials: CS
authors.lastname: Fulco
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Muza
authors.forename: Beth
authors.initials: B
authors.lastname: Beidleman
authors.forename: Juli
authors.initials: J
authors.lastname: Jones
authors.forename: Janet
authors.initials: J
authors.lastname: Staab
authors.forename: Paul B
authors.initials: PB
authors.lastname: Rock
authors.forename: Allen
authors.initials: A
authors.lastname: Cymerman
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000531:Altitude; D000532:Altitude Sickness / Q000517:prevention & control*; D001784:Blood Gas Analysis; D017079:Exercise Tolerance / Q000502:physiology*; D006801:Humans; D008297:Male; D055815:Young Adult