Abstract
This study investigated the relationship between aerobic efficiency during cycling exercise and the increase in physical performance with acute hyperoxic exposure (FiO2 ~31%) (HOX) and also tested the hypothesis that fat oxidation could be increased by acute hyperoxia. Fourteen males and four females were recruited for two sessions, where they exercised for 2 × 10 min at 100 W to determine efficiency. HOX and normoxia (NOX) were administered randomly on both occasions to account for differences in nitrogen exchange. Thereafter, a progressive ramp test was performed to determine VO2max and maximal power output (W max). After 30 min rest, workload was set to 80% of maximal power output (W max) for a time to exhaustion test (TTE). At 100W gross efficiency was reduced from 19.4% during NOX to 18.9% during HOX (P ≤ 0.0001). HOX increased fat oxidation at 100 W by 52% from 3.41 kcal min‐1 to 5.17 kcal min‐1 (P ≤ 0.0001) with a corresponding reduction in carbohydrate oxidation. W max increased by 2.4% from 388.8 (±82.1) during NOX to 397.8 (±83.5) during HOX (P ≤ 0.0001). SaO2 was higher in HOX both at the end of the maximal exercise test and TTE. Subjects with a high level of efficiency in NOX had a larger improvement in Wmax with HOX, in agreement with the hypothesis that an optimum level of efficiency exists that maximizes power production. No association between mitochondrial excess capacity and endurance performance was found; increases in oxygen supply seemed to increase maximal aerobic power production and maintain/increase endurance capacity at the same relative workload.
Highlights
For a number of decades it has been known that exercise performance may be improved by the breathing of hyperoxic gases, the rationale behind this intervention being that more oxygen is delivered to the working tissues, both by an increase in the amount of dissolved oxygen in the blood and by an increase in the saturation of hemoglobin
These effects are made evident by the abolished exercise-induced arterial hypoxemia (EIAH) experienced in some individuals and the increased maximal oxygen consumption (VO2max) shown during severe exercise (Powers et al 1989) Since EIAH is more pronounced in well-trained individuals than those who are more sedentary, it is reasonable to assume that the former group experiences a larger benefit from hyperoxic breathing
After calculating the thermic equivalent from different ratios of substrate oxidation according to Mansell and Macdonald (1990), fat oxidation was increased by 52% from (3.41 kcal minÀ1) in NOX to (5.17 kcal minÀ1) in HOX (P ≤ 0.0001)
Summary
For a number of decades it has been known that exercise performance may be improved by the breathing of hyperoxic gases, the rationale behind this intervention being that more oxygen is delivered to the working tissues, both by an increase in the amount of dissolved oxygen in the blood and by an increase in the saturation of hemoglobin These effects are made evident by the abolished exercise-induced arterial hypoxemia (EIAH) experienced in some individuals and the increased maximal oxygen consumption (VO2max) shown during severe exercise (Powers et al 1989) Since EIAH is more pronounced in well-trained individuals than those who are more sedentary, it is reasonable to assume that the former group experiences a larger benefit from hyperoxic breathing.
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