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 (_baFMD) and whether changes in _baFMD are associated with changes in other cardiovascular health markers in healthy adults; (b) whether intra-individual response differences (IIRD) in _baFMD improvement exist following AT; and (c) the association between participants' baseline characteristics and exercise-induced changes in _baFMD.

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 _baFMD. 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 _baFMD 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 _baFMD, 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 _baFMD 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.