Vascular responsiveness and oxygen transport during exercise in children and adolescents

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Free living movement in the child is highly sporadic, requiring near instantaneous adjustments in metabolism. The rapid adjustment in blood flow needed to support these movement patterns is best assessed from the dynamic response profile and kinetics. Studies in children rarely use dynamic approaches to exercise testing, seldom consider mechanistic pathways or sex and the accurate assessment of key developmental stages is often absent. This research program will overcome some of the limitations of traditional approaches to studying exercise in children by creating novel and integrative insight into how brain blood flow accommodates rapid changes in metabolism at the onset of exercise. In Objective 1, we will define the kinetic cerebrovascular response to acute exercise of varying intensities and the relationship to sex, age, and maturation. In Objective 2, we will develop an understanding of the regulatory mechanisms underpinning adaptations to acute exercise in early-and late-pubertal girls and boys and in adults. Finally, in Objective 3 we will determine whether participation in exercise training alters the cerebrovascular kinetic response in a developmental manner and if sex and duration of training are important. Overall, the long-term objective of this research program is to better understand how age, sex and maturations influence the factors that govern brain blood flow during exercise. SCIENTIFIC APPROACH: Studies conducted to address these objects use cross-sectional, experimental and longitudinal designs with healthy pre-pubertal and pubertal children and adolescents (8-16 years old; 50% boys) and healthy adults (20-25 years old; 50% male). Our experimental approach incorporates exercise protocols designed to systematically alter the metabolic responses in the child and we evaluate brain blood flow responses using non-invasive ultrasounds measures. Importantly we assess biological age using a minimally invasive technique. NOVELTY AND SIGNIFICANCE: This research programme will provide new information about the factors that regulate brain blood flow during the energetic challenges of exercise in the child, how this differs between girls and boys and how this changes as the child ages and matures. The results from these studies will significantly advance our knowledge of the influence growth and have on cerebrovascular function and has the potential to influence current theories of brain blood flow regulation in the child and adolescent. This work will create a better evidence base from which effective intervention can be designed, establishing whether or not exercise training results in adaptations of cerebrovascular function. Importantly the physiologic factors that determine the cerebrovascular response to exercise and the degree to which these can be altered will be key to developing future research investigating impaired cerebrovascular function due to disease or environment.