EFFECTS OF NORMOBARIC HYPOXIA AND HIGH-INTENSITY INTERVAL TRAINING ON HEMODYNAMICS
The purpose of this study was to evaluate the effects of high-intensity interval training (HIIT) at normobaric hypoxia (NH) on measures of hemodynamics. Ten active adults aged 23±1 years volunteered to complete a HIIT intervention at a randomized condition (sea level (SL); low NH (900m); moderate NH (2500m), high NH (4300m)) separated by 72 hours. After acclimating to the condition for 45 minutes (Rest), participants completed a HIIT intervention consisting of six bouts of high-intensity 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), pulse pressure (PP), and rate pressure product (RPP). They were assessed at Rest, during the final AR (AR6), and five minutes following the final bout of exercise (Post). A two-way repeated analysis of variance (ANOVA) was used to analyze the effects of condition (SL, 900m, 2500m, 4300m) across the repeated factor of time (Rest, AR6, Post) in response to HIIT. There was a significant (p≤0.05) main effect of time for HR, SBP, DBP, MAP, PP, and RPP. At all conditions, HR (SL: Rest: 62±9bpm; AR6: 156±21bpm; Post: 104±15bpm; 900m: Rest: 61±10bpm; AR6: 161±10bpm; Post: 109±19bpm; 2500m: Rest: 64±11bpm; AR6: 167±14bpm; Post: 104±14bpm; 4300m: Rest: 67±14bpm; AR6: 171±11bpm; Post: 111±19bpm) increased following Rest, and AR6 was greater than Post. Additionally, at all conditions, SBP (SL: Rest: 116±7mmHg; AR6: 154±16mmHg; Post: 134±13mmHg; 900m: Rest: 119±8mmHg; AR6: 152±10mmHg; Post: 133±13mmHg; 2500m: Rest: 120±10mmHg; AR6: 153±12mmHg; Post: 136±14mmHg; 4300m: Rest: 116±10mmHg; 4300m AR6: 149±15mmHg; Post: 136±14mmHg) increased following Rest. More so, MAP at Rest was lower than AR6 and Post at SL (Rest: 66±5mmHg; AR6: 69±7mmHg; Post: 60±2mmHg) and 900m (Rest: 68±5mmHg; AR6: 70±8mmHg; Post: 68±7mmHg). At AR6, MAP was higher than Post at 900m. Similarly, PP (SL: Rest: 50±7mmHg; AR6: 85±15mmHg; Post: 64±15mmHg; 900m: Rest: 51±7mmHg; AR6: 82±10mmHg; Post: 63±11mmHg; 2500m: Rest: 48±6mmHg; AR6: 85±14mmHg; Post: 66±10mmHg; 4300m: Rest: 44±6mmHg; AR6: 77±14mmHg; Post: 63±11mmHg) was augmented following Rest at all conditions, and AR6 was higher than Post at SL, at 900m. Finally, RPP (SL: Rest: 71±13mmHg; AR6: 216±42mmHg; Post: 139±21mmHg; 900m: Rest: 73±15mmHg; AR6: 204±34mmHg; Post: 145±28mmHg; 2500m: Rest: 78±17mmHg; AR6: 202±30mmHg; Post: 141±22mmHg; 4300m: Rest: 79±21mmHg; AR6: 208±30mmHg; Post: 152±31mmHg) increased following Rest, and Post was lower than AR6, at all conditions. No other significant main effects, conditions, or interactions were observed. While both NH and HIIT increase measures of hemodynamics, combining HIIT and NH does not further augment such variables. Thus, engaging in HIIT at NH does not increase cardiovascular stress or the risk of experiencing a cardiovascular event compared to HIIT at SL.INTRODUCTION
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