Comparison of the effectiveness of high-intensity interval training in hypoxia and normoxia in healthy male volunteers: A pilot study

Aims. The study investigated the effect of high-intensity interval training in hypoxia and normoxia on serum concentrations of proangiogenic factors, nitric oxide, and inflammatory responses in healthy male volunteers. Methods. Twelve physically active male subjects completed a high-intensity interval training (HIIT) in normoxia (NorTr) and in normobaric hypoxia (HypTr) (FiO2 = 15.2%). The effects of HIIT in hypoxia and normoxia on maximal oxygen uptake, hypoxia-inducible factor-1-alpha, vascular endothelial growth factor, nitric oxide, and cytokines were analyzed. Results. HIIT in hypoxia significantly increases maximal oxygen uptake (p=0.01) levels compared to pretraining levels. Serum hypoxia-inducible factor-1 (p=0.01) and nitric oxide levels (p=0.05), vascular endothelial growth factor (p=0.04), and transforming growth factor-β (p=0.01) levels were increased in response to exercise test after hypoxic training. There was no effect of training conditions for serum baseline angiogenic factors and cytokines (p>0.05) with higher HIF-1α and NO levels after hypoxic training compared to normoxic training (F = 9.1; p<0.01 and F = 5.7; p<0.05, respectively). Conclusions. High-intensity interval training in hypoxia seems to induce beneficial adaptations to exercise mediated via a significant increase in the serum concentrations of proangiogenic factors and serum nitric oxide levels compared to the same training regimen in normoxia.