Effects of high-intensity interval training on cardiovascular health: An umbrella review of systematic reviews and meta-analyses

Objectives: Despite considerable evidence on high-intensity interval training (HIIT) for cardiovascular benefits, overlapping studies and lack of systematic synthesis hinder understanding of its full effects and optimal prescription. This umbrella review synthesizes evidence and summarizes the cardiovascular benefits of HIIT across diverse populations. Methods: We searched Embase, PubMed, Web of Science, and Cochrane Library for systematic reviews and meta-analyses on effects of HIIT on cardiovascular health. Evidence was stratified by population type, overlapping evidence was handled by predefined criteria, quality was assessed using AMSTAR 2, and results were visualized using forest plots. Results: Initially, 1017 studies were retrieved, of which 54 were included. The results revealed that HIIT significantly improved blood pressure (SBP: -5.43 to -2.73 mmHg; DBP: -4.35 to -2.41 mmHg), resting heart rate (-4.35 to -2.17 bpm), and left ventricular ejection fraction (3.51% to 5.52%). Compared with other exercise modalities such as moderate-intensity continuous training, HIIT showed significant improvements in left ventricular ejection fraction (3.13% to 3.24%), left ventricular end-diastolic diameter (-4.69 to -2.55 mm), and flow-mediated dilation (0.35% to 2.57%), with comparable effects on blood pressure and heart rate. Conclusion: HIIT demonstrates advantages over other exercise modalities in improving cardiac structure and volume, with comparable effects on blood pressure and heart rate. These benefits were observed across cardiovascular, metabolic, and apparently healthy populations. However, the current evidence does not support protocol-specific recommendations such as long-interval versus short-interval HIIT, and direct comparisons of different HIIT protocols are needed.