The Relationship Between Peak Aerobic Capacity and Skin Microvascular Reactivity in Middle Aged and Older Adults

Abstract

Endurance trained athletes have a high peak aerobic capacity (V̇O₂ peak) and greater endothelial-mediated vasodilation in many vascular beds including the skin when compared to age- and sex-matched untrained adults. Aerobic exercise training increases V̇O₂ peak and there is some evidence to suggest this may result in part from an improvement in endothelial-cell function in large (e.g., macrovasculature) and small (e.g., microvascular) blood vessels. A potential relationship between V̇O₂ peak and skin microvascular function is understudied especially in older adults where V̇O₂ peak and endothelial cell function decline with aging naturally (i.e., healthy aging) and in response to pathology (e.g., ischemic heart disease (IHD)). This thesis examines V̇O₂ peak and changes in skin blood flow (SkBF) to vasodilatory provocation assessments in middle aged and older adults 47 to73 years with and without IHD in order to identify possible relationships between V̇O₂ peak and vasodilatory capacity within the skin microcirculation. Identification of such a relationship would support an emerging position that the skin microcirculation can serve as a surrogate to study and understand the microvascular function of other tissue beds that are more difficult to interrogate (e.g., cardiac). It may be possible to use the skin microcirculation to monitor and track how exercise training or other interventions influence the control and regulation of blood flow within the body's microvascular beds. The primary finding reported in this thesis is that the vasodilatory capacity within the skin microcirculation assessed by resting provocation assessments (i.e., iontophoresis, local heating and PORH) is not strongly associated with V̇O₂ peak but it is strongly-moderately correlated to absolute VO2 during submaximal exercise and V̇O₂ peak. In general, stronger relationships were observed for patients with IHD compared to those who are healthy. Interestingly, exercise training improved V̇O₂ peak and skin vasodilation in response to provocation; however, the amount of improvement in skin vasodilation for a given improvement in V̇O₂ peak were not proportional implying the changes were independent of one another. Although both skin microvascular function and V̇O₂ peak improved with exercise training, more work is required to elucidate how the two physiologic processes interact and to determine how well changes in skin microvascular regulation reflect microvascular function in other tissues.