The Effects Of Normobaric Hypoxia And High-Intensity Interval Training On Measures Of Hemodynamics

PURPOSE: To evaluate the effects of high-intensity interval training (HIIT) at normobaric hypoxia (NH) on measures of hemodynamics. METHODS: Ten active adults completed a HIIT intervention at a randomized condition (sea level (SL); low NH (900 m); moderate NH (2500 m), high NH (4300 m)). After acclimating to the condition for 45 minutes (Rest), participants completed a HIIT intervention consisting of six bouts of HIIT cycling separated by three minutes and 30 seconds of active recovery (AR). Hemodynamic variables included systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and rate pressure product (RPP). They were assessed at Rest, during the final AR (AR6), and five minutes following the last bout of exercise (Post). 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, AR6, Post). RESULTS: There was a significant (p&It0.05) main effect of time for HR (bpm), SBP (mmHg), DBP (mmHg), MAP (mmHg), and RPP (mmHg). At all conditions, HR (SL: Rest: 62 ± 9; AR6: 156 ± 21; Post: 104 ± 15; 900 m: Rest: 61 ± 10; AR6: 161 ± 10; Post: 109 ± 19; 2500 m: Rest: 64 ± 11; AR6: 167 ± 14; Post: 104 ± 14; 4300 m: Rest: 67 ± 14; AR6: 171 ± 11; Post: 111 ± 19) increased following Rest, and AR6 was greater than Post. Additionally, at all conditions, SBP (SL: Rest: 116 ± 7; AR6: 154 ± 16; Post: 134 ± 13; 900 m: Rest: 119 ± 8; AR6: 152 ± 10; Post: 133 ± 13; 2500 m: Rest: 120 ± 10; AR6: 153 ± 12; Post: 136 ± 14; 4300 m: Rest: 116 ± 10; 4300 m AR6: 149 ± 15; Post: 136 ± 14) increased following Rest. At Rest, MAP was lower than AR6 and Post at SL (Rest: 66 ± 5; AR6: 69 ± 7; Post: 60 ± 2) and 900 m (Rest: 68 ± 5; AR6: 70 ± 8; Post: 68 ± 7), and at 900 m, AR6 was higher than Post. Finally, RPP (SL: Rest: 71 ± 13; AR6: 216 ± 42; Post: 139 ± 21; 900 m: Rest: 73 ± 15; AR6: 204 ± 34; Post: 145 ± 28; 2500 m: Rest: 78 ± 17; AR6: 202 ± 30; Post: 141 ± 22; 4300 m: Rest: 79 ± 21; AR6: 208 ± 30; Post: 152 ± 31) increased following Rest, and Post was lower than AR6, at all conditions. No other significant main effects, conditions, or interactions were observed. CONCLUSIONS: Combining HIIT and NH did not further augment measures of hemodynamics compared to HIIT at SL. Thus, engaging in HIIT at NH does not increase cardiovascular stress or the risk of experiencing a cardiovascular event compared to HIIT at SL.