Author(s): GREGORY, D., PEREIRA, T., GULUZADE, N., MATUSHEWSKI, B., MURIAS, J., KEIR, D., Institution: UNIVERSITY OF WESTERN ONTARIO, Country: CANADA, Abstract-ID: 2236

INTRODUCTION:
Background: High-intensity interval training (HIIT) is often compared to moderate-intensity continuous exercise. However, these comparisons manipulate intensity and obscure whether delivery mode elicits a unique exercise stimulus. Purpose: We compared metabolic and cardiovascular responses between work-, time-, and intensity domain-matched interval and continuous exercise.
METHODS:
Methods: Sixteen adults (8 females; 22±5 years, 171.8±12.2 cm, 73.0±14.0 kg) underwent three laboratory visits including: a step-ramp-step cycling test to determine the power outputs (PO) at gas exchange threshold (GET) and respiratory compensation point (RCP), and two randomized work-, intensity-, and time-matched severe-intensity bouts of interval (HIIT) and continuous (HCT) exercise. HIIT consisted of 10, 45-s work intervals at ~140%RCP with 45-s recovery at 80%GET and HCT involved duration-matched constant-PO cycling above RCP (~101-109%RCP); selected to match total work of HIIT. Open-circuit inert gas breathing-derived cardiac output (Q̇) and blood pressure were measured every other interval in HIIT and at matched time points in HCT. Breath-by-breath gas exchange and heart rate were continuously monitored by transmitter belt and mass spectrometer-pneumotach combination.
RESULTS:
Results: PO averaged 184±78 W in HCT and 240±99 (intervals) and 115±51 W (recoveries) in HIIT. Two-way repeated measures ANOVA revealed main effects of time but not condition for all variables. Peak oxygen uptake did not differ (p=0.438) amongst HIIT (2.81±0.94 L∙min-1), HCT (2.85±1.01 L∙min-1) and ramp exercise (3.01±1.22 L∙min-1). No between-condition differences were observed for peaks in Q̇ (20.7±5.2 vs 19.9±5.6 L∙min-1, HIIT vs HCT, p=0.139), heart rate (180±9 vs 177±11 bpm, p=0.100), stroke volume (116±32 vs 113±32 mL, p=0.271), systolic pressure (179±28 vs 185±32 mmHg, p=0.539), nor arteriovenous oxygen difference (13±22 vs 14±2 mLO2/dL, p=0.167).
CONCLUSION:
Conclusion: HIIT and HCT elicit comparable acute cardiovascular and metabolic responses. Mode of exercise delivery may not alter the stimulus imposed on the cardiovascular system provided intensity is matched.