The Effects Of Normobaric Hypoxia On Measures Of Performance

PURPOSE: To evaluate the effects of high-intensity interval training (HIIT) at normobaric hypoxia (NH) on measures of performance. METHODS: Ten adults completed a HIIT intervention which was randomized by condition: sea level (SL); low NH (900 m); moderate NH (2500 m), high NH (4300 m). The HIIT intervention consisted of six bouts of HIIT cycling separated by three min and 30 sec of active recovery (AR). The first and last bouts of the cycling were maximal effort, while the remaining bouts were 75% of maximal power. Measures of performance included rate of perceived exertion (RPE), mean power (MP), peak power (PP), and fatigue index (FI). Mean power, PP, and FI were assessed in relative (watts/kg) values during the first and last bout of exercise (EX1, EX6), while RPE was assessed after 45 min of acclimation to the condition (Rest) and at the onset of the first and last AR (AR1, AR6). A two-way repeated analysis of variance (ANOVA) was used to analyze the effects of condition (SL, 900 m, 2500 m, 4300 m) across the repeated factor of time (Rest, AR1, AR6) for RPE, and across the repeated factor of time (EX 1, EX 6) for MP, PP, and FI. RESULTS: A significant (p ≤ 0.05) main effect of time was observed for RPE, MP, and PP. Additionally, a significant (p ≤ 0.05) condition by time interaction was observed for PP. Compared to AR1 and AR6, RPE at Rest was attenuated (SL: Rest: 6 ± 0; AR1: 14 ± 3; AR6: 18 ± 2; 900 m: Rest: 6 ± 0; AR1: 12 ± 5; AR6: 17 ± 3; 2500 m: Rest: 6 ± 0; AR1: 14 ± 5; AR6: 17 ± 4; 4300 m: Rest: 6 ± 0; AR1: 13 ± 5; AR6: 17 ± 4), and AR1 was lower than AR6, at all conditions. Further, MP was lower at EX6 compared to EX1 at all conditions (SL: EX1: 7.32 ± 0.81; EX6: 6.24 ± 1.52; 900 m: EX1: 6.93 ± 0.78, EX6: 5.87 ± 0.64; 2500 m: EX1: 7.37 ± 0.83; EX6: 6.23 ± 0.93; 4300 m: EX1: 7.29 ± 1.30, EX6: 6.29 ± 1.36) values. Further, PP was decreased at EX6 compared to EX1 at SL, 900 m, and 2500, but there were no differences between EX1 and EX6 at 4300 m (SL: EX1: 9.85 ± 1.37; EX6 8.26 ± 1.41; 900 m: EX1: 9.22 ± 1.40, EX6: 7.63 ± 1.00; 2500 m: EX1: 9.99 ± 1.33; EX6: 7.89 ± 0.96; 4300 m: EX1: 9.94 ± 2.16, EX6: 9.33 ± 2.20). No other significant main effects of time, condition, or condition by time interactions were observed. CONCLUSIONS: Performing HIIT cycling increases fatigue, however; NH does not further augment these outcomes. As such, engaging in HIIT cycling at NH does not hinder cycling performance.