PMID 31412869

Research
All papers

High-intensity interval training improves metabolic syndrome and body composition in outpatient cardiac rehabilitation patients with myocardial infarction

Dun Y, Thomas RJ, Smith JR, Medina-Inojosa JR, Squires RW, Bonikowske AR, Huang H, Liu S, Olson TP

Question

Is supervised HIIT associated with greater improvements in metabolic syndrome and body composition than MICT among MI patients in early outpatient cardiac rehabilitation?

Summary

In a retrospective Mayo Clinic cardiac rehabilitation cohort, myocardial infarction patients with metabolic syndrome who self-selected HIIT after an initial MICT week improved metabolic syndrome severity, several metabolic risk factors, body fat, lean mass, and VO2peak more than those who continued MICT. The study was observational and selected only people completing all 36 rehabilitation sessions.

Methodology

  • Outpatient cardiac rehabilitation patients after MI with metabolic syndrome.
  • 56 participants.
  • Treadmill, cycle ergometer, or recumbent stepper.
  • Work intervals: 30-60 seconds initially, progressed to 2-4 minutes.
  • Recovery: 1-5 minutes active recovery.
  • Intensity: RPE 15-17 for high intervals; recovery RPE <14.
  • 20-45 minutes.
  • Up to 3 supervised nonconsecutive days/week.
  • 36 CR sessions, usually 12 weeks.
  • Retrospective observational cohort study
  • Metabolic syndrome, Body composition, and VO2peak were tracked.

Outcomes

MetS

HIIT reduced MetS presence and severity more than MICT.

Relative risk 0.5, 95% CI 0.33-0.75, p<.001; MetS z-score change -3.6 +/- 2.9 vs -0.8 +/- 3.8, p<.001.

Improved

Risk factors

HIIT improved waist circumference, fasting glucose, triglycerides, and diastolic blood pressure more than MICT.

FBG -25.8 vs -3.9 mg/dl, p<.001; TG -67.8 vs -10.4 mg/dl, p<.001; DBP -7 vs 0 mmHg, p=.001.

Improved

Body composition

HIIT reduced fat mass/body fat and increased lean mass more than MICT.

Fat mass -2.1 +/- 2.1 vs 0 +/- 2.2 kg, p=.002; lean mass +0.9 +/- 1.9 vs -0.9 +/- 3.2 kg, p=.01.

Improved

VO2peak

HIIT increased VO2peak more than MICT.

Change +5.0 +/- 2.5 vs +1.4 +/- 0.9 ml/kg/min, p=.03.

Improved

Insights

  • RPE-based intervals can be used when beta blockers or other medications make HR targets less reliable.
  • HIIT evidence in cardiac populations depends on supervised CR infrastructure.
  • Retrospective self-selection makes causality weaker despite large improvements.

Limitations

  • Retrospective observational design.
  • Self-selection into HIIT after week 1.
  • Only patients completing all 36 CR sessions and follow-up tests were included.
  • Only 36% women.
  • Not powered for safety.

Safety

  • All included patients completed 36 CR sessions without a major adverse event.
  • The study was not designed or powered to demonstrate HIIT safety after MI.