Context: Few recent studies indicate that short-term repeated-sprint (RS) training in hypoxia (RSH) improves RS performance compared with identical training under normoxic conditions (RSN) in endurance-trained subjects. Purpose: To determine the effects of RSH against RSN on RS performance under normoxic and moderate hypoxic conditions, using a randomized, doubleblind, crossover experimental design. Methods: Fifteen endurance-trained male subjects (age 25 ± 4 y) performed 4 wk of RS training (3 sessions/wk) in normobaric hypoxia (RSH, FiO2 = 13.8%) and normoxia (RSN, FiO2 = 20.9%) in a crossover manner. Before and after completion of training, RS tests were performed on a cycle ergometer with no prior exercise (RSNE), after an incremental exercise test (RSIE), and after a time-trial test (RSTT) in normoxia and hypoxia. Results: Peak power outputs at the incremental exercise test and time-trial performance were unaltered by RSH in normoxia and hypoxia. RS performance was generally enhanced by RSH, as well as RSN, but there were no additional effects of RSH over RSN on peak and mean sprint power output and the number of repeated sprints performed in the RSNE, RSIE, and RSTT trials under normoxic and hypoxic conditions. Conclusions: The present double-blind crossover study indicates that RSH does not improve RS performance compared with RSN in normoxic and hypoxic conditions in endurance-trained subjects. Therefore, caution should be exercised when proposing RSH as an advantageous method to improve exercise performance.
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