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=8

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=<p><bold>Objective:</bold> 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).</p><p><bold>Methods:</bold> We prospectively recruited 29 MI patients after percutaneous coronary intervention who began CR within 2 weeks after hospital discharge. Eleven patients (seven men; four women; age: 61 ± 11 yrs) who completed ≥24 supervised HIIT sessions with metabolic gas exchange measured during HIIT once weekly for 8 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 &lt; 12). Metabolic gas exchange, heart rate (HR), and blood pressure during HIIT were measured.</p><p><bold>Results:</bold> The mean oxygen uptake (<inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>˙</mml:mo></mml:mover><mml:mtext>O</mml:mtext></mml:mrow></mml:math></inline-formula><sub>2</sub>) during HIIs across 88 sessions of HIITs [91 (14)% of <inline-formula><mml:math id="M2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>˙</mml:mo></mml:mover><mml:mtext>O</mml:mtext></mml:mrow></mml:math></inline-formula><sub>2peak</sub>, median (interquartile range, IQR)] was significantly higher than the lower limit of target <inline-formula><mml:math id="M3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>˙</mml:mo></mml:mover><mml:mtext>O</mml:mtext></mml:mrow></mml:math></inline-formula><sub>2</sub> zone (75% of <inline-formula><mml:math id="M4" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>˙</mml:mo></mml:mover><mml:mtext>O</mml:mtext></mml:mrow></mml:math></inline-formula><sub>2peak</sub>) recommended for the HII (<italic>p</italic> &lt; 0.001). Exercise intensity during RPE-prescribed HIITs, determined as %<inline-formula><mml:math id="M5" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>˙</mml:mo></mml:mover><mml:mtext>O</mml:mtext></mml:mrow></mml:math></inline-formula><sub>2peak</sub>, was highly repeatable with intra-class correlations of 0.95 (95% CI 0.86– 0.99, <italic>p</italic> &lt; 0.001). For cardiorespiratory adaptations from the first to the last session of HIIT, treadmill speed, treadmill grade, treadmill power, <inline-formula><mml:math id="M6" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>˙</mml:mo></mml:mover><mml:mtext>O</mml:mtext></mml:mrow></mml:math></inline-formula><sub>2HII</sub>, %<inline-formula><mml:math id="M7" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>˙</mml:mo></mml:mover><mml:mtext>O</mml:mtext></mml:mrow></mml:math></inline-formula><sub>2peak</sub>, and V<sub>E</sub> during HIIs were increased (all <italic>p</italic> &lt; 0.05), while no difference was found for HR, %HR<sub>peak</sub> and systolic blood pressure (all <italic>p</italic> &gt; 0.05). <inline-formula><mml:math id="M8" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>˙</mml:mo></mml:mover><mml:mtext>O</mml:mtext></mml:mrow></mml:math></inline-formula><sub>2peak</sub> increased by an average of 9% from pre-CR to post-CR. No adverse events occurred.</p><p><bold>Conclusion:</bold> 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 <inline-formula><mml:math id="M9" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>˙</mml:mo></mml:mover><mml:mtext>O</mml:mtext></mml:mrow></mml:math></inline-formula><sub>2</sub> during exercise training without increased perception of effort or excessive increases in heart rate or blood pressure.</p>