The effect of hypoxia on the response to interval exercise was determined in eight elite female cyclists during two interval sessions: a sustained 3 x 10-min endurance set (5-min recovery) and a repeat sprint session comprising three sets of 6 x 15-s sprints (work-to-relief ratios were 1:3, 1:2, and 1:1 for the 1st, 2nd, and 3rd sets, respectively, with 3 min between each set). During exercise, cyclists selected their maximum power output and breathed either atmospheric air (normoxia, 20.93% O(2)) or a hypoxic gas mix (hypoxia, 17.42% O(2)). Power output was lower in hypoxia vs. normoxia throughout the endurance set (244 +/- 18 vs. 226 +/- 17, 234 +/- 18 vs. 221 +/- 25, and 235 +/- 18 vs. 221 +/- 25 W for 1st, 2nd, and 3rd sets, respectively; P < 0.05) but was lower only in the latter stages of the second and third sets of the sprints (452 +/- 56 vs. 429 +/- 49 and 403 +/- 54 vs. 373 +/- 43 W, respectively; P < 0.05). Hypoxia lowered blood O(2) saturation during the endurance set (92.9 +/- 2.9 vs. 95.4 +/- 1.5%; P < 0.05) but not during repeat sprints. We conclude that, when elite cyclists select their maximum exercise intensity, both sustained (10 min) and short-term (15 s) power are impaired during hypoxia, which simulated moderate ( approximately 2,100 m) altitude.
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