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.