ATG5 and Atrophy: Similarly, no significant change was observed in mRNA expression of Atrogin1, ATG5, or myostatin by real-time RT-PCR, demonstrating that unlike the previous report [6] in which 8% O2 hypoxia induced significant glycolytic reduction of the muscle fiber area in the extensor digitorum longus muscle, the intensity of continuous and intermittent 16% O2 hypoxia was too low to cause glycolytic muscular atrophy.