Adaptation to Exercise Training in Conduit Arteries and Cutaneous Microvessels in Humans: An Optical Coherence Tomography Study

Introduction Exercise training has antiatherogenic effects on conduit and resistance artery function and structure in humans and induces angiogenic changes in skeletal muscle. However, training-induced adaptation in cutaneous microvessels is poorly understood, partly because of technological limitations. Optical coherence tomography (OCT) is a novel high-resolution imaging technique capable of visualizing cutaneous microvasculature at a resolution of 30 μm. We utilized OCT to visualize the effects of training on cutaneous microvessels, alongside assessment of conduit artery flow-mediated dilation (FMD). Methods We assessed brachial FMD and cutaneous microcirculatory responses at rest and in response to local heating and reactive hyperemia: pretraining and posttraining in eight healthy men compared with age-matched untrained controls (n = 8). Participants in the training group underwent supervised cycling at 80% maximal heart rate three times a week for 8 wk. Results We found a significant interaction (P = 0.04) whereby an increase in FMD was observed after training (post 9.83% ± 3.27% vs pre 6.97% ± 1.77%, P = 0.01), with this posttraining value higher compared with the control group (6.9% ± 2.87%, P = 0.027). FMD was not altered in the controls (P = 0.894). There was a significant interaction for OCT-derived speed (P = 0.038) whereby a significant decrease in the local disk heating response was observed after training (post 98.6 ± 3.9 μm·s-1 vs pre 102 ± 5 μm·s-1, P = 0.012), whereas no changes were observed for OCT-derived speed in the control group (P = 0.877). Other OCT responses (diameter, flow rate, and density) to local heating and reactive hyperemia were unaffected by training. Conclusions Our findings suggest that vascular adaptation to exercise training is not uniform across all levels of the arterial tree; although exercise training improves larger artery function, this was not accompanied by unequivocal evidence for cutaneous microvascular adaptation in young healthy subjects.