Background: Regular exercise is associated with enhanced nitric oxide (NO) bioavailability. Flow-mediated dilation (FMD) is used widely to assess endothelial function (EF) and NO release.
Objectives: The aims of this systematic review and meta-analysis were to (i) investigate the effect of exercise modalities (aerobic, resistance or combined) on FMD; and (ii) determine which exercise and participant characteristics are most effective in improving FMD.
Methods: We searched the MEDLINE, Embase, Cochrane Library, and Scopus databases for studies that met the following criteria: (i) randomized controlled trials of exercise with comparative non-exercise, usual care or sedentary groups; (ii) duration of exercise intervention ≥4 weeks; (iii) age ≥18 years; and (iv) EF measured by FMD before and after the intervention. Weighted mean differences (WMDs) with 95% confidence interval were entered into a random effect model to estimate the pooled effect of the exercise interventions.
Results: All exercise modalities enhanced EF significantly: aerobic (WMD 2.79, 95% CI 2.12-3.45, p = 0.0001), resistance (WMD 2.52, 95% CI 1.11-3.93, p = 0.0001) and combined (WMD 2.07, 95% CI 0.70-3.44, p = 0.003). A dose-response relationship was observed between aerobic exercise intensity and improvement in EF. A 2 metabolic equivalents (MET) increase in absolute exercise intensity or a 10% increase in relative exercise intensity resulted in a 1% unit improvement in FMD. There was a positive relationship between frequency of resistance exercise sessions and improvement in EF (β 1.14, CI 0.16-2.12, p = 0.027).
Conclusions: All exercise modalities improve EF significantly and there was a significant, positive relationship between aerobic exercise intensity and EF. Greater frequency, rather than intensity, of resistance exercise training enhanced EF.