Low-Volume and High-Intensity Aerobic Interval Training May Attenuate Dysfunctional Ventricular Remodeling after Myocardial Infarction: Data from the INTERFARCT Study.

Background: Aerobic high-intensity interval training (HIIT) has demonstrated benefits for ventricular remodeling after myocardial infarction (MI) through various mechanisms. Despite this, the optimal training volume is not well known. The present study aimed to assess the effects of different (low vs. high volume) aerobic HIIT compared to an attentional control (AC) group on echocardiographic and biochemical indicators of left ventricular (LV) remodeling in adults after MI. Methods: Randomized clinical trial conducted on post-MI patients with preserved ventricular function. Participants were assigned to three study groups. Two groups performed HIIT 2 d/week, one group with low-volume HIIT (20 min, n = 28) and another with high-volume HIIT (40 min, n = 28). A third group was assigned to AC (n = 24) with recommendations for unsupervised aerobic training. Left ventricular echocardiographic parameters and cardiac biomarker levels (N-terminal pro-b-type natriuretic peptide, NT-proBNP; soluble growth stimulation expressed gene 2, ST2; troponin T; and creatine kinase) were assessed at baseline and after the intervention (16 weeks). Results: Eighty participants (58.4 ± 8.3 yrs, 82.5% male) were included. Both low- and high-volume HIIT showed increases (p < 0.05) in left ventricular end-diastolic diameter (1.2%, 2.6%), and volume (1.1%, 1.3%), respectively. Interventricular septal and posterior walls maintained their thickness (p = 0.36) concerning the AC. Significant (p < 0.05) gain in diastolic function was shown with the improvements in E (-2.1%, -3.3%), e' waves (2.2%, 5.5%), and the deceleration time (2.1%, 2.9%), and in systolic function with a reduction in global longitudinal strain (-3.2%, -4.7%), respectively. Significant (p < 0.05) reductions of N-terminal pro-B-type natriuretic peptide (NT-proBNP) (-4.8%, -11.1%) and of ST2 (-21.7%, -16.7%)were found in both HIIT groups respectively compared to the AC group. Creatine kinase elevation was shown only in high-volume HIIT (19.3%, p < 0.01). Conclusions: Low-volume HIIT is proposed as a clinically time-efficient and safer strategy to attenuate dysfunctional remodeling by preventing wall thinning and improving LV function in post-MI patients.

Vascular-endothelial adaptations following low and high volumes of high-intensity interval training in patients after myocardial infarction.

BACKGROUND: Determinants of coronary artery disease, such as endothelial dysfunction and oxidative stress, could be attenuated by high-intensity aerobic interval exercise training (HIIT). However, the volume of this type of training is not well established. OBJECTIVE: To assess the impact of two volumes of HIIT, low (LV-HIIT, <10 min at high intensity) and high (HV-HIIT, >10 min at high intensity), on vascular-endothelial function in individuals after an acute myocardial infarction (AMI). MATERIALS AND METHODS: Clinical trial in 80 AMI patients (58.4 ± 8.3 years, 82.5% men) with three study groups: LV-HIIT (n = 28) and HV-HIIT (n = 28) with two sessions per week for 16 weeks and control group (CG, n = 24) with unsupervised physical activity recommendations. Endothelial function (brachial flow-mediated dilation, FMD), atherosclerosis (carotid intima-media thickness ultrasound, cIMT), and levels of oxidized low-density lipoprotein (ox-LDL) as a marker of oxidative stress were determined before and after the intervention period. RESULTS: After the intervention, in the exercise groups, there was an increase in FMD (LV-HIIT, ↑58.8%; HV-HIIT, ↑94.1%; p < 0.001) concurrently with a decrease in cIMT (LV-HIIT, ↓3.0%; HV-HIIT, ↓3.2%; p = 0.019) and LDLox (LV-HIIT, ↓5.2%; HV-HIIT, ↓8.9%; p < 0.001), with no significant changes in the CG. Furthermore, a significant inverse correlation was observed between ox-LDL and endothelial function related to the volume of HIIT training performed (LV-HIIT: r = -0.376, p = 0.031; HV-HIIT: r = -0.490, p < 0.004), with no significance in the CG (r = 0.021, p = 0.924). CONCLUSION: In post-AMI patients, HIIT may lead to a volume-dependent enhancement in endothelial function, attributed to a decrease in oxidative stress, with added beneficial effects in reducing vascular wall thickness. An LV-HIIT program, with less than 10 min at high intensity per session, has proven enough efficiency to initiate favorable vascular-endothelial adaptations, potentially reducing cardiovascular risk among patients with coronary artery disease. TRIAL REGISTRATION: INTERFARCT, ClinicalTrials.gov: NCT02876952.

Chronotropic Responses to Exercise and Recovery in Myocardial Infarction Patients Taking ß-Blockers Following Aerobic High-Intensity Interval Training: AN INTERFARCT STUDY.

PURPOSE: The objectives of this study were to compare the effects of two different high-intensity interval training (HIIT) programs (low-volume vs high-volume) on chronotropic responses during exercise and recovery, and to contrast the results of the HIIT groups together to only physical activity recommendations in post-myocardial infarction (MI) patients taking ß-blockers. METHODS: Resting heart rate (HRrest), peak HR (HRpeak), HR reserve (HRreserve = HRpeak-HRrest), HR recovery (HRR) as the difference between HRpeak and post-exercise HR, and chronotropic incompetence were assessed in 70 patients (58 ± 8 yr) following MI with a cardiopulmonary exercise test to peak exertion before and after a 16-wk exercise intervention period. All participants were randomized to either attention control (AC) (physical activity recommendations) or one of the two supervised HIIT groups (2 d/wk). RESULTS: After the intervention, no significant between-HIIT group differences were observed. The HRpeak increased (P < .05) in low- (Δ= 8 ± 18%) and high-volume HIIT (Δ= 6 ± 9%), with a small decrease in AC (Δ=- 2 ± 12%, P > .05) resulting in large differences (P < .05) between HIIT and AC. The HRreserve increased (P < .05) in high-volume HIIT. The HRR slightly increased (P < .05) in low-volume (5th min, Δ= 19 ± 31%) and high-volume HIIT (2nd min, Δ= 15 ± 29%, and 5th min, Δ= 19 ± 28%). CONCLUSION: These findings suggest that both low- and high-volume HIIT elicit similar improvements in chronotropic responses after MI, independent of ß-blocker treatment. Supervised HIIT was more effective than giving physical activity recommendations alone. Low-volume HIIT is presented as a potent and time-efficient exercise strategy that could enhance the sympathovagal balance in this population.

Sex Differences in Cardiometabolic Health Indicators after HIIT in Patients with Coronary Artery Disease.

PURPOSE: Cardiorespiratory fitness (CRF) is an independent predictor of mortality, and females typically achieve smaller improvements in CRF than males after exercise-based cardiac rehabilitation. High-intensity interval training (HIIT) has been shown to produce superior improvements in CRF than traditional cardiac rehabilitation, but the sex differences are unknown. The purpose of this systematic review and meta-analysis was to evaluate sex differences for changes in CRF and cardiometabolic health indicators after HIIT in adults with coronary artery disease (CAD). METHODS AND RESULTS: A systemic search of five electronic databases for studies examining the effect of HIIT on measured CRF and cardiometabolic health indicators in adults with CAD was performed. Data (published and unpublished) from 14 studies were included in the meta-analyses with approximately eightfold greater male than female participation (n = 836 vs n = 103). Males with CAD achieved a near-significant absolute improvement in CRF (mean difference [MD] = 1.07, 95% confidence interval [CI] = -0.08 to 2.23 mL·kg-1⋅min-1, P = 0.07) after HIIT when compared with control; there were insufficient data to conduct such an analysis in females. Significantly smaller improvements in CRF were experienced by females than males (MD = -1.10, 95% CI = -2.08 to -0.12 mL·kg-1⋅min-1, P = 0.03); there was no sex difference for the relative (percentage) change in CRF after HIIT. Females achieved significantly smaller reductions in body mass index (MD = -0.25, 95% CI = -0.03 to -0.47 kg·m-2, P = 0.02) and fasting blood glucose (MD = -0.38, 95% CI = -0.05 to -0.72, P = 0.03); no sex differences were observed for other cardiometabolic health indicators. CONCLUSION: There are no sex differences for relative improvements in CRF after HIIT; however, females are greatly underrepresented in trials. Future studies should increase female participation and perform sex-based analyses to determine sex-specific outcomes following HIIT.

Low-Volume High-Intensity Aerobic Interval Training Is an Efficient Method to Improve Cardiorespiratory Fitness After Myocardial Infarction: PILOT STUDY FROM THE INTERFARCT PROJECT.

PURPOSE: To analyze the changes in cardiorespiratory fitness (CRF) and body composition following 2 different (low-volume vs high-volume) high-intensity aerobic interval training (HIIT) programs with Mediterranean diet (Mediet) recommendations in individuals after myocardial infarction (MI) and compared with an attention control group (AC). METHODS: Body composition and CRF were assessed before and after a 16-wk intervention in 70 participants (58.4 ± 8.5 yr) diagnosed with MI. All participants received Mediet recommendations and were randomly assigned to the AC group (physical activity recommendations, n = 14) or one of the 2 supervised aerobic exercise groups (2 d/wk training): high-volume (40 min) HIIT (n = 28) and low-volume (20 min) HIIT (n = 28). RESULTS: Following the intervention, no significant changes were seen in the AC group and no differences between HIIT groups were found in any of the studied variables. Only HIIT groups showed reductions in waist circumference (low-volume HIIT, Δ = -4%, P < .05; high-volume HIIT, Δ = -2%, P < .001) and improvements in CRF (low-volume HIIT, Δ = 15%, P < .01; high-volume HIIT, Δ = 22%; P < .001) with significant between-group differences (attention control vs HIIT groups). CONCLUSIONS: Results suggest that a 16-wk intervention (2 d/wk) of different HIIT volumes with Mediet recommendations could equally improve CRF and waist circumference after MI. Low-volume HIIT may be a potent and time-efficient exercise training strategy to improve functional capacity.

Effects of combined high-intensity aerobic interval training program and Mediterranean diet recommendations after myocardial infarction (INTERFARCT Project): study protocol for a randomized controlled trial.

BACKGROUND: Exercise therapy has long been used for rehabilitation purposes after myocardial infarction (MI) and the benefit of regular physical exercise is also well-established. High-intensity interval training (HIIT) has been proposed to be more effective than continuous exercise for improving exercise capacity and health-related adaptations to low-volume (LV) and HIIT are also known. Furthermore, the Mediterranean diet (Mediet) has been widely reported to be a model of healthy eating for its contribution to a favorable health status and a better quality of life, reducing overall mortality. This study will investigate the effects of different HIIT programs (high-volume [HV] vs LV) and Mediet recommendations in clinical condition, cardiorespiratory fitness, biomarkers, ventricular function, and perception of quality of life after MI, and compared to an attention control group that is recommended to Mediet and physical activity without supervision sessions. METHODS/DESIGN: In this randomized controlled trial, cardiorespiratory fitness, anthropometry, central and peripheral cardiovascular variables, biochemical and nutritional condition, and quality of life will be assessed before and after 16 weeks of intervention in 177 participants diagnosed with MI type 1. All participants will be randomly (1:1:1) assigned to the attention control group or two exercise groups (Mediet recommendations plus supervised aerobic exercise two days/week: (1) HV (40 min) HIIT group and (2) LV (20 min) HIIT group. DISCUSSION: This study will be the first clinical trial comparing the effects of two different volumes of HIIT programs with Mediet recommendations for people after MI. The results of this study will provide good evidence for physical rehabilitation in this population. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02876952 . Registered on 24 August 2016.