High-intensity interval training versus moderate-intensity continuous training on exercise capacity and health-related quality of life in patients with coronary artery disease: An updated systematic review and meta-analysis

Background: Despite the well-known positive effects of exercise in patients with coronary artery disease, the best exercise training protocol is still under discussion. Objective: We performed a systematic review and a meta-analysis to investigate the effects of high-intensity interval training (HIIT) versus moderate-intensity continuous training (MICT) on exercise capacity and healthrelated quality of life (HRQoL) in patients with coronary artery disease. Methods: We searched MEDLINE/PubMed, the Cochrane Library EMBASE, and the PEDro database for randomized controlled trials that evaluated the effects of HIIT versus MICT. Mean difference and 95 % confidence intervals (CI) were calculated. Results: 27 studies, with 1454 patients, met the eligibility criteria. Twenty-four studies with 1259 patients assessed peak oxygen consumption (VO2peak) as an outcome. The HIIT group showed an increase of VO2peak (MD = 2.11 mL/kg/min; 95 % CI: 1.14, 3.07; I2 = 78 %; N = 1259) compared with the MICT group. Six studies with 316 patients assessed HRQoL as outcome. No differences in physical, emotional, and social domains of HRQoL were found between the HIIT and MICT groups. In the subgroup analysis of 10 studies with isocaloric exercise training, the HIIT and MICT groups showed similar VO2peak (MD = 0.72 mL/kg/min; 95 % CI:0.03, 1.48; I2 = 44 %; N = 453). Conclusions: Our meta-analysis showed low-quality evidence that HIIT training was more effective than MICT for improving VO2peak but not HRQoL in patients with coronary artery disease. However, when the analysis was limited to isocaloric protocols no difference between HIIT and MICT was found for VO2peak.