Effect of Various Regimes of High Intensity Interval Training (HIIT) on Changes in Maximal Oxygen Uptake and Hemodynamic Function

Abstract

Data (Burgomaster et al. 2008; Astorino et al. 2013) demonstrate improved maximal oxygen uptake (VO2max) after 6 and 12 wk of high intensity interval training (HIIT) which enhances exercise performance and health status. A few studies (Daussin et al. 2008; MacPherson et al. 2011) document changes in cardiac output (CO) in response to HIIT in which increases in VO2max occurred, and their results are equivocal. PURPOSE: To examine changes in VO2max and CO in response to various regimes of HIIT. METHODS: Fifty active men and women were randomized to control (CON, n = 24, age = 25.3 ± 4.7 yr) or one of three HIIT regimes, HIIT + sprint interval training (SIT) (n = 10, age = 22.8 ± 7.0 yr), HIIT + HIIT (n = 8, age = 21.8 ± 2.2 yr), or HIIT + periodized training (PER) (n = 8, age = 24.4 ± 6.8 yr). Training was performed 3 d/wk for 6 wk, with 10 sessions of HIIT (6 – 10 bouts of cycling for 60 s separated by 75 s recovery at 90 – 110 % peak power output) completed followed by randomization to one of three regimes for the ensuing 3 wk of the study. VO2max was measured pre- and post-training during progressive exercise, during which pulmonary gas exchange data were obtained. Cardiac output, heart rate (HR), and stroke volume (SV) were continuously estimated using thoracic impedance (Physioflow Enduro). Participants maintained their habitual physical activity during the study, and prior to all assessments, they abstained from exercise for 48 h. RESULTS: VO2max was unchanged in CON, yet a significant groupXtime interaction (p < 0.01) was demonstrated showing higher VO2max in HIIT + SIT (2.85 ± 0.47 L/min to 3.08 ± 0.34 L/min), HIIT + HIIT (2.81 ± 0.62 L/min to 3.02 ± 0.73 L/min), and HIIT + PER (2.64 ± 0.77 L/min to 2.92 ± 0.78 L/min). A significant groupXtime interaction (p = 0.038) was revealed for HR in that it was higher through HIIT. Stroke volume differed across time (p = 0.009) but no interaction occurred (p = 0.31). Cardiac output differed across time (p = 0.006) and a significant groupXtime interaction (p = 0.032) was shown. Compared to CON (20.9 ± 3.3 L/min to 20.8 ± 3.2 L/min), CO was increased in HIIT + SIT (19.9 ± 2.5 L/min to 21.4 ± 1.0 L/min), HIIT + HIIT (21.1 ± 4.0 L/min to 22.2 ± 2.7 L/min), and HIIT + PER (20.0 ± 3.7 L/min to 21.6 ± 4.4 L/min). CONCLUSION: Similar increases in VO2max occur in response to various regimes of HIIT, with greater CO explaining this outcome.