title: GXT responses in altitude-acclimatized cyclists during sea-level simulation.
abstract: OBJECTIVE
  This study examined the effects of gender on graded exercise stress test (GXT) response in moderate-altitude (MA)-acclimatized cyclists during sea-level (SL) simulation. It was hypothesized that alterations in arterial saturation would relate to changes in VO2peak.
  
  
  METHODS
  Twenty competitive cyclists (12 males, 8 females) who were residents of MA locations underwent two randomized bicycle GXTs: one under local normoxic hypobaria, and the other under simulated SL conditions.
  
  
  RESULTS
  Under the SL condition, the cyclists demonstrated a significant increase (2-3%) in absolute and relative VO2peak, improved (4%) economy at lactate threshold (LT), and time-adjusted peak power (7%); the range of improvement between individuals varied from -6% to +25%. Simulated SL also resulted in a greater arterial saturation (S(a)O2) at rest and VO2peak, and significantly less desaturation (4 vs 8%) from rest to VO2peak. The individual variability in the change (Delta) in VO2peak was not significantly correlated to SL S(a)O2 or any other S(a)O2 variable analyzed, regardless of whether we examined each gender individually or combined. Significant correlations were found between Delta-peak power and Delta-economy as well as Delta-VO2peak and Delta-GXT time. These correlations as well as degree of improvement varied by gender.
  
  
  CONCLUSIONS
  These data suggest that chronic residence at MA may attenuate the occurrence of exercise-induced arterial hypoxemia and eliminate the relationship between S(a)O2 and Delta-VO2peak that has been reported among SL residents acutely exposed to altitude. Additionally, the improvements that occur in predictors of aerobic performance when MA residents are exposed acutely to SL conditions have a large degree of individual variability, and the mechanism(s) for improvement may vary by gender.
authors.affiliation: Department of Integrative Physiology, University of Colorado, Boulder, CO, USA. michael.brothers@colorado.edu
authors.forename: Michael D
authors.initials: MD
authors.lastname: Brothers
authors.forename: Kristin
authors.initials: K
authors.lastname: Hilger
authors.forename: John M
authors.initials: JM
authors.lastname: Carson
authors.forename: Luisa
authors.initials: L
authors.lastname: Sullivan
authors.forename: William C
authors.initials: WC
authors.lastname: Byrnes
mesh_terms: D000064:Acclimatization; D000328:Adult; D000531:Altitude; D001642:Bicycling / Q000502:physiology*; D003120:Colorado; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods*; D045853:Exhalation / Q000502:physiology; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000209:etiology; D019344:Lactic Acid / Q000032:analysis; D008297:Male; D008448:Maximal Expiratory Flow Rate / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology
chemical_list: D019344:Lactic Acid