Metabolic Effects of Breathing Hyperoxic Gas Mixtures During Heavy Exercise

Abstract

The extent to which hyperoxia influences whole body metabolism and glycogen utilization during submaximal exercise was studied in seven males. Subjects completed two 30-min exercise bouts on a bicycle ergometer at 80% of maximum aerobic power under normoxic and hyperoxic conditions. During each submaximal exercise session, oxygen consumption (V̇O₂), ventilation (V̇_E), heart rate, and blood lactate were measured. Before and after each submaximal task, a muscle biopsy was taken from the vastus lateralis muscle and analyzed biochemically to determine muscle glycogen levels. V̇O₂, V̇CO₂, and muscle glycogen utilization were similar under the two conditions. Although the respiratory exchange ratio (RER) was significantly reduced under hyperoxia, the magnitude of the difference was small (0.04 RER units). Under hyperoxia, blood lactate was significantly lowered, which may reflect an enhanced conversion of pyruvate to alanine. The observed significant decrease in V̇_E and heart rate under hyperoxia may reflect responses of the peripheral chemo- and baroreceptors.

Key words

normoxia - hyperoxia - glycogen - oxygen consumption - carbon dioxide production - blood lactate