Distinct Effects of Repeated-Sprint Training in Normobaric Hypoxia and β-Alanine Supplementation

Objective: The present study evaluated the effects of repeated-sprint training in normobaric hypoxia and β-alanine supplementation (BA) on aerobic and anaerobic performance in recreationally active men. Methods: Participants were randomly assigned to one of the following groups: normoxia/β-alanine (NB, n = 11), normoxia/placebo (NP, n = 8), normobaric hypoxia/β-alanine (HB, n = 10) and normobaric hypoxia/placebo (HP, n = 9). All participants completed 8 training sessions over 4 weeks on a cycle ergometer either in normobaric hypoxia (oxygen fraction: FiO ₂ = 14.2%) or normoxia (FiO ₂ = 20.9%). Participants were instructed to consume a daily dosage of 6.4 g of BA or placebo. Changes in performance in a graded exercise test, repeated-sprint test (RST), and 3-minute all-out test (3MT) were examined before and after training and supplementation. Results: No between-group differences were observed for training volume or supplementation compliance. Anthropometric and hematological measures remained unchanged before and after intervention in all groups. A main effect of training condition was shown for oxygen consumption and power output at respiratory compensation point, average power output during the last sprint of the RST, heart rate recovery following the RST, and total work during the 3MT. These measures in the normobaric hypoxia groups were significantly (p < 0.05) higher than the normoxia groups, except for the heart rate recovery following the RST. A main effect of supplement was detected in anaerobic working capacity, with postintervention values in the BA groups being significantly (p < 0.05) higher than the placebo groups. Conclusions: Repeated-sprint training in hypoxia improved aerobic performance, exercise tolerance, cardiovascular recovery, and overall working capacity, while BA maintained the anaerobic working capacity. However, BA did not provide additional benefits with respect to attenuating fatigue or enhancing repeated-sprint performance.