All arteries and veins in the body are lined by a single layer of cells called the endothelium. A healthy endothelium protects arteries and helps resist atherosclerosis. On the other hand, endothelial dysfunction is a hallmark of cardiovascular disease (CVD).
Exercise effectively improves endothelial function, yet the impact of different modalities and intensities remains unclear.
A new study evaluated the effect of aerobic (AE), resistance (RE), and combined exercise (CE) on endothelial function measured by flow-mediated dilation (FMD).
A review and meta-analysis of randomized and non-randomized trials in adults with coronary artery disease or chronic heart failure was conducted. Electronic databases were searched up to April 2025.
Exercise interventions were classified as usual care (UC), moderate-intensity AE (MAE), high-intensity interval AE (HIIE), moderate-intensity RE (MRE), high-intensity RE (HRE), moderate-intensity CE (MCE), and high-intensity CE (HCE). Thirty-seven studies (80 groups; n = 6818) were included.
Compared with UC, MAE, HIIE, MCE, and HCE significantly improved brachial FMD, whereas MRE did not.
HIIE outperformed MAE. Although HCE showed the highest surface under the cumulative ranking curve, this relied on a single group. Sensitivity analyses confirmed HIIE as the most robust high-performing intervention.
Exercise significantly enhances endothelial function in patients with CVD. What kind of exercise is best is debatable.
In this study, HIIE emerged as the most robust and evidence-based modality, demonstrating superior efficacy over moderate continuous exercise. While high-intensity combined protocols (HCE) show significant theoretical potential, randomized trials are urgently needed to confirm their efficacy. Current evidence supports HIIE as a primary strategy for vascular adaptation in cardiac rehabilitation.
The results suggest that HIIE could be integrated as a primary or complementary strategy within cardiac rehabilitation programs, provided it is performed under appropriate clinical supervision.
The study also highlights that exercise-induced improvements were specific to endothelial function, with no significant changes observed in endothelium-independent vasodilation. This indicates that adaptations occur primarily at the endothelial level rather than in vascular smooth muscle.
Beyond identifying the most effective modality, the study underscores that not all forms of exercise produce the same physiological benefits. Intensity, structure, and individual patient characteristics play a decisive role in vascular adaptation.
HIIE exercise modality alternates short bursts of high-intensity effort with recovery periods. This pattern generates repeated fluctuations in blood flow and shear stress—the frictional force exerted by blood on vessel walls—which are key stimuli for endothelial adaptation.
Increased shear stress enhances nitric oxide (NO) bioavailability, a critical mediator of vasodilation and vascular health. These mechanisms explain why higher-intensity exercise produces stronger endothelial responses than moderate continuous training.
