Metabolic response during intermittent graded sprint running in moderate hypobaric hypoxia in competitive...

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 degrees 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]. V(O2) at each speed was lower in H than N (ANOVA; P < 0.05). Although, oxygen deficit (D(O2)) at each speed was not different between N and H (ANOVA; P = 0.1), total accumulated D(O2) 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 D(O2).V(O2)(-1) 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.