# High-intensity interval training versus progressive high-intensity circuit resistance training on endothelial function and cardiorespiratory fitness in heart failure: A preliminary randomized controlled trial PMID: 34597330 Journal: PloS one Published: 2021-10-01 Authors: Turri-Silva N, Vale-Lira A, Verboven K, Quaglioti Durigan JL, Hansen D, Cipriano G Jr ## Question Do high-intensity interval training and progressive high-intensity circuit resistance training improve endothelial function and cardiorespiratory fitness, and secondarily muscle strength and physical performance, in stable heart failure patients? ## Summary In a small preliminary randomized trial of stable heart failure patients, 36 supervised sessions of aerobic HIIT and progressive high-intensity circuit resistance training improved cardiorespiratory fitness versus control, but neither training mode improved brachial artery flow-mediated dilation. HIIT showed broader improvements in cycling peak power, isokinetic strength-related measures, and global physical performance, while CRT improved chair-stand time. No medical complications occurred during training. ## Population - Stable heart failure patients on optimal medical therapy, including reduced, mid-range, and preserved ejection fraction classifications. - Sample size: 23 - Age: Mean age by group 55.0 to 60.9 years. - Sex: Male participants: HIIT 5/8, CRT 4/6, control 7/8. - Fitness level: Low cardiorespiratory fitness typical of HF; baseline VO2 peak approximately 16.9 to 20.2 mL/kg/min. - Health status: Stable heart failure, mostly NYHA I-II with some NYHA III; common cardiovascular risk factors. ## Methodology - Preliminary longitudinal parallel randomized controlled trial with three groups: HIIT, circuit-resistance training, and control. - 36 exercise sessions, 3 sessions/week; control follow-up was 12 weeks. - Exercise center/cardiovascular rehabilitation research setting at the University of Brasilia, Brazil; training supervised by physiotherapists with a cardiologist available. - Randomized and controlled study design. ## Protocol - Supervised aerobic HIIT. - Modality: Treadmill and cycle ergometer alternated by session. - Work intervals: 3 minutes high intensity. - Recovery: 4 minutes moderate intensity. - Sets or repetitions: Four 7-minute cycles. - Intensity: High intensity based on CPET-derived HR zones: above the moderate upper limit by up to 10%; moderate intensity around VT1. - Session duration: Approximately 50 minutes, including 10 minutes moderate aerobic work before 28-minute HIIT block. - Frequency: 3 sessions/week. - Program length: 36 sessions. - Progression: 6-10 session familiarization; load increased by speed and then incline if speed was not tolerated. - Progressive high-intensity circuit resistance training and routine control. - Modality: Machine-based circuit resistance training; no-training routine control. - Work intervals: CRT used resistance sets rather than timed work intervals. - Recovery: 1 minute rest between exercises. - Sets or repetitions: 3 circuit series of six exercises; repetitions varied from 6-12 early in each month to 15-20 late in each month. - Intensity: 50% 1RM during familiarization, then 60% 1RM month 1, 70% month 2, 80% month 3. - Session duration: Approximately 50 minutes. - Frequency: 3 sessions/week. - Program length: 36 sessions. - Progression: Monthly 1RM-based load progression with repetition variation. ## Outcomes ### Endothelial function Status: no clear change Neither HIIT nor CRT improved FMD compared with baseline or control. FMD change: HIIT -0.36 (95% CI -5.05 to 4.33), CRT +0.42 (-3.86 to 4.70), control +0.90 (-4.35 to 6.14); between-group differences not significant. ### VO2 peak Status: improved VO2 peak improved within both HIIT and CRT, while control did not improve. HIIT +2.2 mL/kg/min (95% CI 0.2 to 4.1), CRT +3.1 (0.8 to 5.3), control -0.1 (-2.0 to 1.9); abstract reports time*group p<0.05. ### Cycling peak power and strength Status: mixed HIIT improved cycling peak power output and several strength-related measures; CRT had smaller or nonsignificant strength changes. HIIT cycling peak power +18.1 W (95% CI 4.4 to 31.9); HIIT isokinetic torque peak/body weight +12.1% (1.8 to 22.4); average power +20.8 W (4.7 to 36.8). ### Physical performance Status: mixed CRT improved chair-stand completion time, and HIIT improved global physical performance according to authors. CRT chair stand seconds -3.3 (95% CI -6.5 to -0.2); total SPPB time/group result p=0.008. ### Safety Status: no clear change No medical complications were reported during supervised training sessions. ## Practical Insights - In stable HF, high-intensity interval work can be feasible when medically screened, monitored, and supervised. - A familiarization period may be important before requiring target high-intensity intervals in clinical populations. - Fitness benefits should not be assumed to imply vascular endothelial benefits. ## Limitations - Preliminary small trial stopped early because of COVID-19. - Missing outcome data for FMD, SPPB, and muscle strength. - Only one center provided data despite multicenter adaptation. - Results are not directly generalizable to unsupervised consumer HIIT or unstable HF. ## Safety And Adherence - No medical complications occurred during training sessions. - Physiotherapists monitored BP, HR, RPE, excessive tiredness, sweating, paleness, palpitations, and chest pain. - A cardiologist was available in case of health concerns. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/34597330/) (pubmed) - [DOI](https://doi.org/10.1371/journal.pone.0257607) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8486136/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.