The aim of this study was to test the hypothesis that intermittent hypoxic interval training improves sea level cycling performance more than equivalent training in hypoxia or normoxia.Methods:
Thirty-three well-trained cyclists and triathletes (25.9 ± 2.7 yr, V̇O2max 66.1 ± 6.1 mL·min−1·kg−1) were divided into three groups: intermittent hypoxic (IHT, N = 11, PIO2 of 100 mm Hg), intermittent hypoxic interval training (IHIT, N = 11) and normoxia (Nor, N = 11, PIO2 of 160 mm Hg) and completed a 7-wk training program, consisting of two high-intensity (100 or 90% relative peak power output) interval training sessions each week. Each interval training session was performed in a laboratory on the subject's own bicycle, in normoxic or hypoxic conditions for the Nor and the IHT group, respectively. The IHIT group performed warm-up and cool-down plus recovery from each interval in hypoxic conditions. In contrast to IHT, interval exercise bouts were performed in normoxic conditions.Results:
Mean power output during a 10-min cycle time trial improved after the first 4 wk of training by 5.2 ± 3.9, 3.7 ± 5.9, and 5.0 ± 3.4% for IHIT, IHT, and Nor, respectively, without significant differences between groups. Moreover, mean power output did not show any significant improvement in the following 3 wk in any group. V̇O2max (L·min−1) increased only in IHIT during the training period (8.7 ± 9.1%; P < 0.05). No changes in cycling efficiency or in hematological variables (P > 0.05) were observed.Conclusion:
Four weeks of interval training induced an improvement in endurance performance. However, short-term exposure to hypoxia (∼114 min·wk−1) did not elicit a greater increase in performance or any hematological modifications.