Metabolic response during intermittent graded sprint running in moderate hypobaric hypoxia in competitive middle-distance runners

The purpose of this study was to determine whether the metabolic response and running performance during intermittent graded sprint running were affected by moderate hypobaric hypoxia (H; 2,500 m above sea level) in competitive middle-distance runners. Nine male runners performed intermittent graded sprint running until exhaustion, to evaluate the metabolic response and running performance in H and normobaric normoxia (N). The test constructed of incremental (25 m min⁻¹) 20 s running bouts (4° inclination) interspaced with 100 s recovery periods. Maximal running speed was not different between conditions [453 (7) m min⁻¹ vs. 458 (4) m min⁻¹ in N vs. H]. at each speed was lower in H than N (ANOVA; P < 0.05). Although, oxygen deficit at each speed was not different between N and H (ANOVA; P = 0.1), total accumulated in all bouts was significantly higher in H than N [165 (10) ml kg⁻¹ in N and 173 (10) ml kg⁻¹ in H]. The ratio of was similar in all bouts, but higher in H than N. These results suggest that intermittent graded sprint running performance is not affected by moderate hypobaria despite a reduction in the energy supplied by aerobic metabolism due to a compensatory increase in the energy supplied by the anaerobic metabolism in competitive middle-distance runners.