Intermittent normobaric hypoxia does not alter performance or erythropoietic markers in highly trained distance runners

This study was designed to test the hypothesis that intermittent normobaric hypoxia at rest is a sufficient stimulus to elicit changes in physiological measures associated with improved performance in highly trained distance runners. Fourteen national-class distance runners completed a 4-wk regimen (5:5-min hypoxia-to-normoxia ratio for 70 min, 5 times/wk) of intermittent normobaric hypoxia (Hyp) or placebo control (Norm) at rest. The experimental group was exposed to a graded decline in fraction of inspired O2: 0.12 (week 1), 0.11 (week 2), and 0.10 (weeks 3 and 4). The placebo control group was exposed to the same temporal regimen but breathed fraction of inspired O2 of 0.209 for the entire 4 wk. Subjects were matched for training history, gender, and baseline measures of maximal O2 uptake and 3,000-m time-trial performance in a randomized, balanced, double-blind design. These parameters, along with submaximal treadmill performance (economy, heart rate, lactate, and ventilation), were measured in duplic...