Effects of aerobic training on brachial artery flow-mediated dilation in healthy adults: a meta-analysis of inter-individual response differences in randomized controlled trials.

BACKGROUND

This study aimed to investigate: (a) the effects of aerobic training (AT) on brachial artery endothelial function, measured by flow-mediated dilatation (FMD) and whether changes in FMD are associated with changes in other cardiovascular health markers in healthy adults; (b) whether intra-individual response differences (IIRD) in FMD improvement exist following AT; and (c) the association between participants' baseline characteristics and exercise-induced changes in FMD.

METHODS

The search conducted across six databases (PubMed, Web of Science, CINAHL, EMBASE, the Cochrane Central Register of Controlled Trials, and EBSCOhost) identified 12 eligible studies. We conducted both traditional meta-analyses identifying the effects of the intervention and IIRD. IIRD meta-analysis was performed to assess if true IIRD between AT and the control group exists for FMD. The methodological quality of included studies was assessed by the PEDro scale, while GRADE assessment was used for certainty of evidence evaluation.

RESULTS

In total, 12 studies with 385 participants (51% male, 46.3 ± 17.3 [years]) were included in the current review. Meta-analysis revealed improvement in FMD post-AT (small MD = 1.92%, 95% CI 0.90 to 2.94, p = 0.001). The standard deviation of change scores in the intervention and control groups suggests that most of the variation in the observed change from pre-to-post intervention is due to other factors (e.g., measurement error, biological variability etc.) unrelated to the intervention itself. However, subgroup meta-analysis revealed that significantly trivial IIRD exists following AT in prehypertensive individuals.

CONCLUSIONS

The study found small improvements in FMD, suggesting an average 19.2% reduction in cardiovascular disease (CVD) risk, with some individuals-such as prehypertensive individuals-potentially experiencing even greater benefits from AT. However, a meta-analysis based on IIRD suggests that factors unrelated to AT predominantly explain FMD changes. Further research is needed to better understand response variability in individuals with cardiovascular risk factors, and longer studies are required to assess IIRD in the general population.