NORMOBARIC EXPOSURE DOES NOT ALTER HYPOBARIC AEROBIC PERFORMANCE
Muza, S., Fulco, C., Beidleman, B., Jones, J., Staab, J., Elliott, S., Lammi, E., & Cymeerman, A. (2009). Lowlander time-trial performance at 4300m is not improved following normobaric intermittent hypoxic exposure conditioning. ACSM 55th Annual Meeting Indianapolis, Presentation Number, 1263.
"Normobaric intermittent hypoxic exposure conditioning may induce beneficial physiological adaptations that improve physical performance during subsequent ascents to high altitudes." This study determined if three hours in a hypoxia room exercising 65% HRmax, repeated for 6-7 consecutive days, improved cycle time trial performance at 4,300 m (in a hypobaric chamber) approximately 60 hours after the last exposure. Male lowlanders (N = 17) were initially exposed to 4300 m (446 mm Hg), followed by ~12 days of sea level residence to deacclimatize. Then 11 received the true intermittent hypoxic exposure treatment, and six received a sham intermittent hypoxic exposure treatment followed by 2.5 days of no intermittent hypoxic exposure before the second exposure to 4300 m.
Over 6-7 days of intermittent hypoxic exposure sessions, true intermittent hypoxic exposure resting SaO2 increased while the sham condition did not change. Seven Ss could not complete the time trial at 4300 m. Thus, time trial analysis was limited to the time to reach the halfway point. Compared to the first hypobaric exposure, after intermittent hypoxic exposure there was no improvement in time trial performance in either group and no difference between groups.
Implication. Although the intermittent hypoxic exposure treatment protocol induced ventilatory acclimatization in normobaric hypoxia, no performance benefits were present at high altitude 2.5 days after the intermittent hypoxic exposure ended. This suggests that intermittent normobaric hypoxic exposure does not induce adaptations beneficial to improving exercise performance in a hypobaric environment.
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