Effects of exercise training with intermittent hyperoxic intervention on endurance performance and muscle metabolic properties in male mice

This study aimed to investigate how intermittent hyperoxic exposure (three cycles of 21% O2 [10 min] and 30% O2 [15 min]) affects exercise performance in mice. Three hours after the acute exposure, there was an observed increase in mRNA levels of phosphofructokinase (Bayes factor [BF] >= 10), mitochondrial transcription factor-A (BF >= 10), PPAR-alpha (BF >= 3), and PPAR-gamma (BF >= 3) in the red gastrocnemius muscle (Gr). Four weeks of exercise training under intermittent (INT), but not continuous (HYP), hyperoxia significantly (BF >= 30) increased maximal exercise capacity compared to normoxic exercise-trained (ET) group. INT group exhibited significantly higher activity levels of 3-hydroxyacyl-CoA-dehydrogenase (HAD) in Gr (BF = 7.9) compared to ET group. Pyruvate dehydrogenase complex activity levels were significantly higher in INT group compared to ET group in white gastrocnemius, diaphragm, and left ventricle (BF >= 3). NT-PGC1 alpha protein levels in Gr (BF = 7.7) and HAD activity levels in Gr (BF = 6.9) and soleus muscles (BF = 3.3) showed a significant positive correlation with maximal work values. These findings suggest that exercise training under intermittent hyperoxia is a beneficial strategy for enhancing endurance performance by improving fatty acid and pyruvic acid utilization.