# Effect of maximal-intensity and high-intensity interval training on exercise capacity and quality of life in patients with acute myocardial infarction: a randomized controlled trial PMID: 37906165 Journal: European Journal of Physical and Rehabilitation Medicine Published: 2024-02-01 Authors: Nam H, Jeon HE, Kim WH, Joa KL, Lee H ## Question In low-to-moderate-risk patients after acute myocardial infarction, how do MIIT, HIIT, and usual care compare for exercise capacity, health-related quality of life, psychological symptoms, and safety during phase II cardiac rehabilitation? ## Summary This randomized controlled trial compared 9 weeks of hospital-based maximal-intensity interval training (MIIT), hospital-based high-intensity interval training (HIIT), and usual care in adults after acute myocardial infarction who were at low or moderate cardiac rehabilitation risk. MIIT improved VO2max more than HIIT and usual care, while both MIIT and HIIT improved health-related quality of life more than usual care. No heart-related adverse events were reported during the intervention, although three hospital-based participants reported pre-existing chronic musculoskeletal pain. ## Population - Ninety-one adults after acute MI treated with primary PCI and classified as low or moderate cardiac rehabilitation risk. - Sample size: 91 - Age: Mean ages by group: MIIT 56.07 +/- 10.48 years, HIIT 58.69 +/- 12.38, usual care 56.66 +/- 9.50. - Sex: Women by group: MIIT 3/30, HIIT 4/29, usual care 4/32. - Fitness level: Baseline VO2max by group: MIIT 27.54 +/- 6.29, HIIT 26.73 +/- 8.11, usual care 27.91 +/- 6.85 mL/kg/min. - Health status: Post-acute myocardial infarction after primary PCI; low-to-moderate AACVPR cardiac rehabilitation risk; high-risk and exercise-contraindicated patients excluded. ## Methodology - Prospective, single-blinded, three-group pre-test/post-test randomized controlled study with a nonrandomized usual-care allocation based on participant preference for home or community exercise. - 9 weeks total, including a 2-week adaptation period and 7 weeks of incrementally increased interval training. - Outpatient hospital-based phase II cardiac rehabilitation and home/community usual care in Korea. - Randomized and controlled study design. ## Protocol - MIIT phase II cardiac rehabilitation. - Modality: Treadmill aerobic interval training. - Work intervals: Four 4-minute intervals at 95-100% VO2max. - Recovery: 3-minute active rest at 60% VO2max. - Sets or repetitions: Four 4x4 sets. - Intensity: 95-100% VO2max during work intervals after adaptation. - Session duration: 50 minutes. - Frequency: Twice weekly. - Program length: 9 weeks. - Progression: 2-week adaptation period followed by incremental intensity increase over 7 weeks. - HIIT phase II cardiac rehabilitation plus usual care comparator. - Modality: Treadmill aerobic interval training for HIIT; self-directed home/community exercise for usual care. - Work intervals: HIIT: four 4-minute intervals at 85% VO2max; usual care: not specified. - Recovery: HIIT: 3-minute active rest at 60% VO2max; usual care: not specified. - Sets or repetitions: HIIT: four 4x4 sets; usual care: not specified. - Intensity: HIIT: 85% VO2max during work intervals; usual care: RPE 11-13 instruction at first visit. - Session duration: HIIT: 50 minutes; usual care: not restricted or monitored. - Frequency: HIIT: twice weekly; usual care: not monitored. - Program length: 9 weeks. - Progression: HIIT used the same 2-week adaptation and 7-week progression structure as MIIT; usual-care progression not reported. ## Outcomes ### VO2max Status: improved VO2max improved in all groups, with MIIT greater than HIIT and usual care. Time x group F=30.70, p<0.001; MD MIIT 7.85 (95% CI 6.65-9.05), HIIT 4.60 (3.16-6.03), usual care 1.41 (0.44-2.38); post-hoc a>b>c ### MacNew global HRQoL Status: improved MIIT and HIIT improved MacNew global more than usual care. F=4.99, p=0.010; MD MIIT 0.55 (0.35-0.75), HIIT 0.60 (0.43-0.77), usual care 0.24 (0.07-0.42); b=a>c ### MacNew physical HRQoL Status: improved MIIT and HIIT improved MacNew physical more than usual care. F=3.32, p=0.042; MD MIIT 0.66 (0.34-0.97), HIIT 0.58 (0.36-0.80), usual care 0.23 (0.01-0.48); a=b>c ### MacNew emotional HRQoL Status: improved MIIT and HIIT improved MacNew emotional more than usual care. F=4.56, p=0.013; post-hoc hospital-based groups greater than usual care ### MacNew social HRQoL Status: no clear change No significant time x group interaction was observed for the social subdomain. F=1.18, p=0.311 ### 6MWT Status: improved 6MWT improved significantly in all groups; MIIT differed from usual care, while MIIT and HIIT did not differ. HIIT MD 57.86 m (95% CI 37.06-78.66); usual care MD 18.84 m (8.58-29.11); HIIT vs MIIT p=0.148, HIIT vs usual care p=0.269, MIIT vs usual care p=0.002 ### Psychological outcomes Status: mixed PHQ showed a significant time x group interaction with HIIT improving versus usual care, but FSS, PSQI, KASI, GAD, and PCL-5 had no significant interactions. PHQ p=0.025; HIIT MD -2.21 (95% CI -3.58 to -0.83); FSS p=0.225, PSQI p=0.195, KASI p=0.360, GAD p=0.176, PCL-5 p=0.251 ### Safety Status: no clear change No heart-related adverse events were reported in MIIT or HIIT during 9 weeks; three participants reported pre-existing chronic musculoskeletal pain. ## Practical Insights - In medically screened, monitored post-MI cardiac rehabilitation, increasing 4x4 interval intensity from 85% to 95-100% VO2max produced larger VO2max gains over 9 weeks. - Both MIIT and HIIT improved HRQoL compared with usual care, suggesting hospital-based interval CR benefits extend beyond VO2max. - Safety findings are bounded by low-to-moderate cardiac risk, PCI-treated acute MI, clinical supervision, and continuous monitoring. ## Limitations - Usual-care allocation was based on preference for home/community exercise rather than the same randomization process used for MIIT vs HIIT. - No follow-up assessment for long-term effects. - Specific low-to-moderate-risk post-MI population limits generalization to other recovery stages or high-risk patients. - Usual-care exercise compliance was not monitored. - Group-specific attendance and interval-completion fidelity were not reported. ## Safety And Adherence - No heart-related adverse events, including heart attack, ventricular tachycardia, recurrence of MI, or severe chest pain, were reported during the intervention period. - Two MIIT participants and one HIIT participant reported musculoskeletal pain, described as chronic pain that started before cardiac rehabilitation. - High-risk cardiac rehabilitation patients and those with exercise contraindications were excluded. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/37906165/) (pubmed) - [DOI](https://doi.org/10.23736/S1973-9087.23.08094-2) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10938035/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.