Effects of Exercise on Vascular Function, Structure, and Health in Humans

Abstract

Physical activity has profound impacts on the vasculature in humans. Acute exercise induces immediate changes in artery function, whereas repeated episodic bouts of exercise induce chronic functional adaptation and, ultimately, structural arterial remodeling. The nature of these changes in function and structure are dependent on the characteristics of the training load and may be modulated by other factors such as exercise-induced inflammation and oxidative stress. The clinical implications of these physiological adaptations are profound. Exercise impacts on the development of atherosclerosis and on the incidence of primary and secondary cardiovascular events, including myocardial infarction and stroke. Exercise also plays a role in the amelioration of other chronic diseases that possess a vascular etiology, including diabetes and dementia. The mechanisms responsible for these effects of exercise on the vasculature are both primary and secondary in nature, in that the benefits conferred by changes in cardiovascular risk factors such as lipid profiles and blood pressure occur in concert with direct effects of arterial shear stress and mechanotransduction. From an evolutionary perspective, exercise is an essential stimulus for the maintenance of vascular health: exercise is vascular medicine.

Figure 1.

Hemodynamic stimuli and their effects on vascular function and adaptation. (From Green et al. 2017; adapted, with permission.)

Figure 2.

Some examples of studies investigating the impacts of exercise training in humans, including studies using plethysmography and intrabrachial infusion of agonists and antagonists of endothelial pathways (Maiorana et al. 2000) and conduit artery functional assessment using flow-mediated dilation (FMD) (Maiorana et al. 2001). FBF, Forearm blood flow.

Figure 3.

Summary of a bench-to-bedside study incorporating in vivo (A), in situ, and in vitro (B) evidence for shear mediated adaptation in endothelial function in humans as a result of exercise training (Hambrecht et al. 2003). (From Green et al. 2017; adapted, with permission.) Studies were performed on the internal mammary artery. eNOS, Endothelial nitric oxide synthase.

Figure 4.

High-resolution duplex ultrasound image of a brachial artery. Software enables continuous edge-detection and wall tracking of the B mode image, whereas the velocity envelope is also automatically recorded (live feedback of tracking is seen as the yellow tracing). Simultaneous velocity and diameter measures are recoded and saved at ∼30 Hz, and output generated (left). Output includes continuous diameter tracing, blood flow, and shear rate (other variables are also available including velocity, pressure, etc.). These tracings illustrate a typical flow-mediated dilation (FMD) response as a result of 5 min of limb ischemia. Note the large blood flow/shear rate response to cuff deflation and the biphasic (increase and then decrease) response in diameter. FMD is endothelium-dependent and largely nitric oxide (NO)-mediated (Green et al. 2011) and provides a surrogate index of conduit artery function and health in humans (Thijssen et al. 2011a). Longer periods of cuff ischemia, or cuff ischemia whereas performing exercise (e.g., ischemic handgrip), result in maximal diameter and blood flow responses (Naylor et al. 2005) that provide valuable information regarding structural changes (e.g., lumenal enlargement in response to exercise training) in resistance arteries downstream from the conduit arteries. See text for further explanation.

Figure 5.

Impact of manipulating blood flow and shear stress during exercise bouts on the magnitude of functional and structural adaptation to exercise training in humans. These studies all adopted the use of a cuff on one limb to unilaterally decrease shear stress responses to handgrip exercise, leg exercise, forearm heating and leg heating. In all cases, an increase in shear stress was necessary for adaptations in arterial function and/or structure to be expressed (see Green et al. 2017 for further details). Note the pattern of change in function that is typically superseded by changes in structure, particularly in response to handgrip and leg exercise training. FMD, Flow-mediated dilation; IHG, isometric handgrip.