Abstract Body (Do not enter title and authors here): Background:
Exercise interventions are foundational in cardiovascular disease prevention and management. High-Intensity Interval Training (HIIT) and Moderate-Intensity Continuous Training (MICT) are widely studied modalities, yet their comparative efficacy on cardiovascular outcomes remains debated.

Objective:
To evaluate and compare the effects of HIIT and MICT on cardiovascular outcomes in adults based on randomized controlled trials (RCTs) published from 2015 to 2025.

Methods:
A systematic search of studies exported from EndNote identified 27 RCTs meeting the following inclusion criteria: adult participants (≥18 years), English language, publication date between 2015–2025, and comparison of HIIT versus MICT with reported cardiovascular outcomes.
Primary outcomes included peak oxygen uptake (VO2 peak), left ventricular function, endothelial function, blood pressure, lipid profiles, and adverse cardiovascular events. Data were extracted and pooled using a random-effects model. Standardized mean differences (SMDs) and risk ratios (RRs) were calculated with 95% confidence intervals (CIs). Heterogeneity was assessed using I^2 statistics.

Results:
Across 27 RCTs (n = 2,743 participants), HIIT significantly improved VO2 peak compared to MICT (SMD: 0.51; 95% CI: 0.34–0.68; p < 0.001; I^2 = 43%). Left ventricular ejection fraction (LVEF) improved modestly with HIIT (SMD: 0.24; 95% CI: 0.10–0.38; p = 0.001). HIIT also demonstrated greater reductions in systolic blood pressure (mean difference: –5.6; 95% CI: –7.2 to –4.0; p < 0.001) and improved endothelial function (flow-mediated dilation: SMD: 0.39; 95% CI: 0.19–0.58; p < 0.001). No significant difference was observed in major adverse cardiovascular events between groups (RR: 0.96; 95% CI: 0.84–1.09; p = 0.51). Adherence and safety profiles were comparable between HIIT and MICT.

Conclusion:
HIIT demonstrates superior improvements in cardiorespiratory fitness, ventricular function, and vascular health compared to MICT in adults, with similar safety and adherence. These findings support the incorporation of HIIT as an effective alternative or adjunct to MICT in cardiovascular prevention and rehabilitation programs. Further long-term studies are warranted to assess the impacts on clinical cardiovascular events.