AUTHOR=Dun Yaoshan , Hammer Shane M. , Smith Joshua R. , MacGillivray Mary C. , Simmons Benjamin S. , Squires Ray W. , Liu Suixin , Olson Thomas P. 

TITLE=Cardiorespiratory Responses During High-Intensity Interval Training Prescribed by Rating of Perceived Exertion in Patients After Myocardial Infarction Enrolled in Early Outpatient Cardiac Rehabilitation

JOURNAL=Frontiers in Cardiovascular Medicine

VOLUME=Volume 8 - 2021

YEAR=2022

URL=https://www.frontiersin.org/journals/cardiovascular-medicine/articles/10.3389/fcvm.2021.772815

DOI=10.3389/fcvm.2021.772815

ISSN=2297-055X

ABSTRACT=Objective: We aimed to determine the cardiorespiratory responses during, and adaptations to, high-intensity interval training (HIIT) prescribed using ratings of perceived exertion (RPE) in patients after myocardial infarction (MI) during early outpatient cardiac rehabilitation (CR). 

Methods: We prospectively recruited 29 MI patients after percutaneous coronary intervention who began CR within two weeks after hospital discharge. Eleven patients (7 men; 4 women; age: 61 ± 11 yrs) who completed ≥24 supervised HIIT sessions with metabolic gas exchange measured during HIIT once weekly for eight weeks and performed pre- and post- CR cardiopulmonary exercise tests were included in the study. Each HIIT session consisted of 5-8 high-intensity intervals (HIIs, 1-min RPE 14-17 [Borg 6-20 scale]) and low-intensity intervals (LIIs, 4-min RPE < 12). Metabolic gas exchange, heart rate (HR), and blood pressure during HIIT were measured. 

Results: The mean oxygen uptake (V̇O2) during HIIs across 88 sessions of HIITs (91 [14]% of V̇O2peak, median [interquartile range, IQR]) was significantly higher than the lower limit of target V̇O2 zone (75% of V̇O2peak) recommended for the HII (p<0.001). Exercise intensity during RPE-prescribed HIITs, determined as %V̇O2peak, was highly repeatable with intra-class correlations of 0.95 (95% CI 0.86 to 0.99, p<0.001). For cardiorespiratory adaptations from the first to the last session of HIIT, treadmill speed, treadmill grade, treadmill power, V̇O2 HII, %V̇O2peak, and V̇E during HIIs were increased (all p<0.05), while no difference was found for HR, %HRpeak and systolic blood pressure (all p>0.05). V̇O2peak increased by an average of 9% from pre-CR to post-CR. No adverse events occurred. 

Conclusion: Our results demonstrate that HIIT can be effectively prescribed using RPE in MI patients during early outpatient CR. Participation in RPE-prescribed HIIT increases exercise workload and V̇O2 during exercise training without increased perception of effort or excessive increases in heart rate or blood pressure.