Simulated hypoxia does not further improve aerobic capacity during sprint interval training

Aim. The aim of this study was to investigate the use of hypoxic sprint interval training (SIT) for the improvement of aerobic capacity. Method. Twenty-seven participants (mean +/- SD), age 21 +/- 1 yrs, body mass 72.4 +/- 9.7 kg and height 175 +/- 7 cm, completed an (V) over dotO(2peak) Incremental Exercise Test and time to exhaustion (TTE) trial (80% (V) over dotO(2peak)) pre and post SIT. Participants were randomly assigned to either, control (CONT), normoxic (NORM) or hypoxic (FiO(2): 0.15) (HYP) conditions. SIT involved 30s sprints interspersed with 4min rest. The number of sprints progressed from four to seven over six sessions separated by 1-2 days rest. Two-way mixed design ANOVA was performed to determine changes between conditions. Results. (V) over dotO(2peak) improved (P<0.05) pre to post SIT in NORM (11.2 +/- 10.8%) and HYP (10.9 +/- 6.2%), but not CONT (0.7 +/- 14.3%). TTE post SIT was significantly improved from pre SIT in NORM and HYP but not CONT (CONT=1 +/- 6, NORM=56 +/- 25, HYP=34 +/- 25%, P<0.05). Peak and recovery heart rate was lower in NORM (P<0.05) than HYP as SIT sessions progressed. SpO(2) (%) was lower in HYP (86.1 +/- 4.3%) compared to NORM (97.1 +/- 0.7%), decreasing within all HYP sessions, and increasing with SIT. Conclusion. Hypoxic and normoxic SIT caused improvement in (V) over dotO(2peak) and TTE compared to a control. Hypoxic SIT did not cause further improvements, indicating hypoxia based SIT offers no additional benefit for improvement of endurance performance.