Modeling cerebrovascular dynamics during transitions in exercise intensity.

Cerebral blood flow is a tightly controlled variable that is regulated by multiple integrative physiological mechanisms. Many of the factors that influence cerebral blood flow change during exercise in an intensity-dependent manner, leading to complex interactions, with the net effect of all factors dictating the blood flow response. Research to-date has largely focused on investigating cerebrovascular responses to exercise during discrete steady-state stages, but recently, dynamic modeling of the cerebrovascular response to transitions in exercise intensity has gained interest as a novel way to study cerebrovascular health and function. Indeed, studying the dynamic adjustment of a variable in response to an external stimulus provides important information about the integrity and function of the controlling system. In the context of the cerebrovascular response to exercise, it is important to recognize that the primary stimulus inducing a change in cerebral blood flow is not simply just an increase in external work being performed, but rather the integrative exercise response that includes changes in arterial blood pressure, cardiac output, arterial partial pressure of carbon dioxide, autonomic nervous system activity, and cerebral metabolism. However, disentangling the contribution of separate factors and mechanisms to the dynamic cerebrovascular response to exercise is complicated. Accordingly, in this review we 1) provide an overview of different modeling approaches that have been applied to investigate cerebrovascular kinetics during exercise transitions, 2) discuss considerations when modeling cerebrovascular responses to exercise, and 3) provide perspectives to help inform modeling approaches for future work.