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

Background To examine the effect of high-intensity interval training (HIIT) on metabolic syndrome (MetS) and body composition in cardiac rehabilitation (CR) patients with myocardial infarction (MI). Methods We retrospectively screened 174 consecutive patients with MetS enrolled in CR following MI between 2015 and 2018. We included 56 patients who completed 36 CR sessions and pre-post dual-energy X-ray absorptiometry. Of these patients, 42 engaged in HIIT and 14 in moderate-intensity continuous training (MICT). HIIT included 4-8 intervals of high-intensity (30-60 s at RPE 15-17 [Borg 6-20]) and low-intensity (1-5 min at RPE < 14), and MICT included 20-45 min of exercise at RPE 12-14. MetS and body composition variables were compared between MICT and HIIT groups. Results Compared to MICT, HIIT demonstrated greater reductions in MetS (relative risk = 0.5, 95% CI 0.33-0.75, P < .001), MetS z-score (- 3.6 +/- 2.9 vs. - 0.8 +/- 3.8, P < .001) and improved MetS components: waist circumference (- 3 +/- 5 vs. 1 +/- 5 cm, P = .01), fasting blood glucose (- 25.8 +/- 34.8 vs. - 3.9 +/- 25.8 mg/dl, P < .001), triglycerides (- 67.8 +/- 86.7 vs. - 10.4 +/- 105.3 mg/dl, P < .001), and diastolic blood pressure (- 7 +/- 11 vs. 0 +/- 13 mmHg, P = .001). HIIT group demonstrated greater reductions in body fat mass (- 2.1 +/- 2.1 vs. 0 +/- 2.2 kg, P = .002), with increased body lean mass (0.9 +/- 1.9 vs. - 0.9 +/- 3.2 kg, P = .01) than the MICT. After matching for exercise energy expenditure, HIIT-induced improvements persisted for MetS z-score (P < .001), MetS components (P < .05), body fat mass (P = .002), body fat (P = .01), and lean mass (P = .03). Conclusions Our data suggest that, compared to MICT, supervised HIIT results in greater improvements in MetS and body composition in MI patients with MetS undergoing CR.