Influence of Acute Moderate Hypoxia on Time to Exhaustion at vV˙O₂max in Unacclimatized Runners

Abstract

Eight unacclimatized long-distance runners performed, on a level treadmill, an incremental test to determine the maximal oxygen uptake (V˙O₂max) and the minimal velocity eliciting V˙O₂max (vV˙O₂max) in normoxia (N) and acute moderate hypoxia (H) corresponding to an altitude of 2400 m (PIO₂ of 109 mmHg). Afterwards, on separate days, they performed two all-out constant velocity runs at vV˙O₂max in a random order (one in N and the other in H). The decrease in V˙O₂max between N and H showed a great degree of variability amongst subjects as V˙O₂max decreased by 8.9 ± 4 ml × min^-1 × kg^-1 in H vs. N conditions (-15.3 ± 6.3 % with a range from -7.9 % to -23.8 %). This decrease in V˙O₂max was proportional to the value of V˙O₂max (V˙O₂max vs. delta V˙O₂max N-H, r = 0.75, p = 0.03). The time run at vV˙O₂max was not affected by hypoxia (483 ± 122 vs. 506 ± 148 s, in N and H, respectively, p = 0.37). However, the greater the decrease in vV˙O₂max during hypoxia, the greater the runners increased their time to exhaustion at vV˙O₂max (vV˙O₂max N-H vs. tlim @vV˙O₂max N-H, r = -0.75, p = 0.03). In conclusion, this study showed that there was a positive association between the extent of decrease in vV˙O₂max_, and the increase in run time at vV˙O₂max in hypoxia.

Key words

Exercise - altitude - maximal oxygen uptake - fatigue

References

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