Acute effect of different normobaric hypoxic conditions on shuttle repeated sprint performance in futsal players

Abstract

This study aimed to investigate the acute effects of different environmental oxygen conditions on shuttle repeated sprint performance in futsal players. Using a counterbalanced design, 16 male university-level futsal players performed 3 sets of shuttle repeated sprints (6 × 10 s) over a 5m distance with 20 s active rest between reps and 5 min active rest between sets. Participants completed 4 trials in a random order over 4 weeks with different inspired oxygen fractions for each trial (FIO2 = 20.9%, 14.5%, 13.5% and 12.5%). Electromyography (RMSEMG) data was recorded from the vastus lateralis muscle during sprinting. The number of completed shuttles in each 10 s period, blood lactate concentration, rating of perceived exertion, oxygen saturation (SpO2), and cardiorespiratory variables were recorded after each set. We found that after set3, blood lactate concentration was substantially higher (p <0.05) in the 12.5% FIO2 (10.4 ± 2.1 mmol/L) compared to normoxia, 14.5% or 13.5% condition (5.0 ± 1.6, 7.8 ± 1.5, and 9.4 ± 1.9 mmol/L, respectively). Compared to normoxia, the RMSEMG signal was 34.1% lower in the 12.5% condition, 14.1% and 18.6% lower in the 14.5% and 13.5% oxygen condition respectively. Moreover, SpO2 after set3 was substantially lower (p <0.05) in 12.5% (73.7 ± 3.4%) compared to normoxia, 14.5% or 13.5% condition (95.1 ± 1.8, 81.1 ± 2.1, and 79.1 ± 2.4%, respectively). Overall the lower FIO2 conditions produced lower in number of sprints, and highest heart rate, ventilation and rating of perceived exertion levels. In conclusion, FIO2 13.5% is an appropriate choice for shuttle repeated sprint training in hypoxia. Although, FIO2 13.5% was lower in benefitcial responses than FIO2 12.5% but FIO2 12.5% might produce unnecessary and unwanted fatigue from insufficient oxygen to athletes.