RESUMEN
BACKGROUND/AIMS: In various animal models the application of systemic heat and physical activity (PA) has induced an up-regulation of endothelial nitric oxide synthase. Several experts in the field suggest shear stress as the main mechanism. A review was performed to summarize the results from clinical studies investigating the effect of mild systemic heat (MSH) and PA on endothelium-dependent vasodilation (EDD) in persons at increased cardiovascular risk. METHODS: MEDLINE was searched from 1990 to 2008. Randomized controlled trials (RCTs) investigating the effect of MSH and/or PA on EDD in persons with at least one cardiovascular risk factor were included. RESULTS: For MSH, no RCTs were found, while for PA 12 RCTs could be identified (n = 383 participants). Besides one trial, EDD was assessed as percent flow-mediated dilation (% FMD). Three meta-analyses were performed depending on participants' age as well as type and length of PA intervention. All trials revealed effects in favor of PA compared to a non-intervention control. For example, in a meta-analysis of 3 PA trials including 106 participants and comparing 12-week aerobic exercise with a non-exercise control, EDD was statistically significantly improved (weighted mean difference: 2.14% FMD; 95% confidence interval: 1.12-3.15% FMD). CONCLUSION: The review provides clear evidence that PA improves endothelial function in persons at increased cardiovascular risk. For MSH, evidence from RCTs is lacking. However, because MSH and PA are assumed to be based on the same main mechanism, a comparable effect of MSH on endothelial function may be possible. This should be scrutinized in an RCT.