GXT Responses in Altitude-Acclimatized Cyclists during Sea-Level Simulation


Medicine & Science in Sports & Exercise: October 2007 - Volume 39 - Issue 10 - pp 1727-1735
doi: 10.1249/mss.0b013e3181238a3f
BASIC SCIENCES: Original Investigations

Purpose: 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 V˙O2peak.

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 V˙O2peak, 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 (SaO2) at rest and V˙O2peak, and significantly less desaturation (4 vs 8%) from rest to V˙O2peak. The individual variability in the change (Δ) in V˙O2peak was not significantly correlated to SL SaO2 or any other SaO2 variable analyzed, regardless of whether we examined each gender individually or combined. Significant correlations were found between Δ-peak power and Δ-economy as well as Δ-V˙O2peak and Δ-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 SaO2 and Δ-V˙O2peak 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.

Department of Integrative Physiology, University of Colorado, Boulder, CO

Address for correspondence: Michael D. Brothers, USAFA/ADML Human Performance Lab, 2169 Field House Dr., USAF Academy, CO 80840; E-mail: michael.brothers@colorado.edu.

Submitted for publication November 2006.

Accepted for publication May 2007.

©2007The American College of Sports Medicine