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 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 < 12). Metabolic gas exchange, heart rate (HR), and blood pressure during HIIT were measured.Results: The mean oxygen uptake (2) during HIIs across 88 sessions of HIITs [91 (14)% of 2peak, median (interquartile range, IQR)] was significantly higher than the lower limit of target 2 zone (75% of 2peak) recommended for the HII (p < 0.001). Exercise intensity during RPE-prescribed HIITs, determined as %2peak, was highly repeatable with intra-class correlations of 0.95 (95% CI 0.86– 0.99, p < 0.001). For cardiorespiratory adaptations from the first to the last session of HIIT, treadmill speed, treadmill grade, treadmill power, 2HII, %2peak, and VE during HIIs were increased (all p < 0.05), while no difference was found for HR, %HRpeak and systolic blood pressure (all p > 0.05). 2peak 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 2 during exercise training without increased perception of effort or excessive increases in heart rate or blood pressure.
Highlights
Exercise-based cardiac rehabilitation (CR) is a secondary prevention tool used worldwide to improve physical function and prognosis in patients after myocardial infarction (MI) [1, 2]
The intra-class correlation (ICC) of exercise intensity, %V O2peak, between the Ratings of perceived exertion (RPE)-prescribed High-intensity interval training (HIIT) sessions was 0.95
The values of treadmill speed, treadmill grade, power, V O2, %V O2peak, heart rate (HR), %HRpeak, SBP, VE, VT and f B in the HIIs were significantly greater than those in the LIIs during each exercise session, which was consistent with the values of RPE during the HIIs vs. during the LIIs [15 [2] vs. 11 [2], median (IQR), p < 0.001]
Summary
Exercise-based cardiac rehabilitation (CR) is a secondary prevention tool used worldwide to improve physical function and prognosis in patients after myocardial infarction (MI) [1, 2]. High-intensity interval training (HIIT) has recently emerged as an alternative or adjunct strategy to traditional moderateintensity continuous training [3]. HIIT has been shown to result in similar or greater improvements in aerobic capacity and other health outcomes compared to moderate-intensity continuous training [4]. The relationships between patient safety, perception of effort, and cardiorespiratory responses and adaptations during HIIT sessions in patients after MI have not been reported. Gaps in our understanding of the relationship between effort perception and cardiorespiratory responses limit our ability to provide optimal guidance for prescription, implementation, and safety of HIIT in CR
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