Impact of intermittent elevations in shear rate on peripheral endothelial function

Blood flowing through arteries is a key stimulus for the release of substances that cause vessels to dilate and further increase blood flow. The physiological ability to stimulate dilation in response to increased blood flow is called endothelial function and is an indicator of the overall health of blood vessels. There are a number of ways to increase blood flow including exercise, limb heating, or hypoxia (low oxygen content) all of which can be beneficial to improving vascular health. A large amount of research indicate that a sustained increase in blood flow over time can improve endothelial function and the ability to transport blood. However, it is not well understood if changing the pattern of blood flow in an intermittent pattern produces further benefits. Thus, the present research explored the impact of intermittent elevations in blood flow, induced by hypoxia and handgrip exercise, on improving endothelial function. In our first study we demonstrated that intermittent elevations in blood flow with hypoxia did not necessarily improve endothelial function, however it was able to prevent a decline following inactivity. Intermittent hypoxia also had similar outcomes compared to continuous hypoxia. Our second study demonstrated that increased blood flow via handgrip exercise, significantly improved endothelial function. Key findings suggest the intermittent nature of the exercise and blood flow pattern improved endothelial function more so than continuous/sustained exercise. Collectively, these two studies suggest that not only is increased blood flow important to improve endothelial function, but increases in an intermittent fashion may be more beneficial.