Ogawa, T., Fujii, N., Kurimoto, Y., Honda, Y., & Nishiyasu, T. (2008). The effect of hypobaria on ventilation and VO2max during maximal running. ACSM 55th Annual Meeting Indianapolis, Presentation Number, 1268.

"During hypobaric hypoxia (H), maximal exercise pulmonary ventilation (VEmax) is related to the arterial oxyhemoglobin saturation level (SaO2) and the maximal oxygen uptake (VO2max). Resistance to air flow is one of the factors limiting VEmax. It is therefore likely that the airflow resistance of the airway is reduced during maximal exercise under H conditions, since air density declines with descending atmospheric pressure. It is unknown, however, whether reducing airflow resistance by reducing the atmospheric pressure affects VEmax and thus VO2max, SaO2 and exercise performance."

This study examined the effects of lowering the airflow resistance (hypobaria) or hypobaric normoxia (HN), on VEmax, VO2max, SaO2 and exercise performance (an incremental running test). Young males (N = 10) performed the running tests to exhaustion in a hypobaric chamber under conditions of normoxia and hypobaric normoxia.

VO2max and SaO2 were significantly lower in hypobaric hypoxia than in mormoxia. VEmax did not differ between hypobaric hypoxia and normoxia. VEmax was significantly higher in hypobaric normoxia than in normoxia, although VO2max and SaO2 did not differ between them. Running duration was significantly longer in hypobaric normoxia than in normoxia. "These results suggest that the reduced air density under the 3,500 m hypobaric condition increased VEmax and exercise performance, but a 6.6% increase in VEmax did not affect VO2max and SaO2 under the hypobaric normoxia condition."

Implication. Hypobaria, (hypobaric normoxia) itself induces an increase in VEmax and exercise performance, but VO2max and SaO2 do not change.

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