Impact of training intensity on cardiovascular responses in patients with coronary artery disease: extended systematic review and meta-analysis

Introduction: intensity plays a major role for optimal benefits from exercise for coronary artery disease (CAD) patients. The superior effect between high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) is still uncertain. Objective: To investigate the effect of different aerobic exercise intensities on exercise capacity, hs-CRP, and lipid profile among CAD patients. Methodology: an extensive search was carried out in databases such as PubMed, Scopus, ClinicalKey and ScienceDirect (from the earliest data available to May 2024) for randomised controlled trials comparing HIIT and MICT among CAD patients. Mean differences and 95% confidence interval (CI) were calculated using random effect model in Revman version 5.4, a funnel plot was used for publication bias and heterogeneity was reported using I2 statistics. Results: thirty-five studies were identified, which included 1879 CAD patients. HIIT resulted in a significant improvement in peak VO2 weighted mean difference (1.39 ml/kg/min, p <0.00001, 95% CI: 0.87 – 1.90, n = 1461, I2=0%) compared with MICT. Moreover, HIIT resulted in a significant improvement in total cholesterol (TC) weighted mean difference (-0.08, p = 0.03, 95% CI: -0.15 – -0.01, n = 738, I2=26%) compared with MICT. Both intensities improved in hs-CRP, LDL-C, HDL-C, and TG but there were no statistically significant differences. Conclusions: this study confirmed that HIIT provides greater improvement in peak VO2 and may be an important part of an effective exercise program for CAD patients. More well-designed, randomised controlled trials are needed to establish the safety of HIIT via inflammatory markers.