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Tallon, Christine Marie

University of British Columbia

Despite extensive literature on cerebral blood flow (CBF) regulation and cerebrovascular function in adults, there is very limited knowledge for the healthy child. Equally, as children’s daily sedentary behaviour increases, relationships between sedentary behaviour, physical activity, and cerebral hemodynamics are also poorly understood. This thesis aimed to determine the impact of sedentary behaviour on cerebrovascular function in healthy children. To achieve this objective four studies were conducted. An initial study (Chapter 3) explored relationships between habitual sedentary behaviour, physical activity, maturation, and CBF at rest in 78 children and adolescents (6 – 17 years), observing a lower internal carotid artery (ICA) shear rate in participants who engaged in >452 min of total sedentary behaviour per day. The second and third studies focused on the measurement of cerebrovascular function in children compared to adults and investigated cerebrovascular reactivity [CVR] to inspired carbon dioxide (F₁CO₂; 6%), indexed by temporal blood velocity changes (v) within the middle cerebral artery (MCA; Chapter 4) and blood flow in the ICA (QICA; Chapter 5), per unit of change in the end-tidal partial pressure of CO₂. Findings of Chapter 4 indicate similar CVR MCAv in children (n=21) and adults (n=20), but a significantly slower onset response to CO₂ in children compared to adults. Similarly, findings of Chapter 5 indicate a similar CVR ICA between children (n=14) and adults (n=17) but a slower onset response in the child. Applying knowledge of the relationship identified in Chapter 3, and the methodology used in Chapters 4 and 5, the fourth study (Chapter 6) investigated whether an acute bout of prolonged sitting (3 h) would alter cerebrovascular function and whether interrupting prolonged sitting with exercise breaks (10 min each hour) affords defence against any sitting-induced cerebrovascular disruption in children (n=31). Findings of Chapter 6 indicate an acute bout of prolonged sitting compromises QICA CVR and the MCAv onset response; however, when sitting was interrupted with exercise breaks these declines were prevented. The findings from this thesis have provided novel evidence of the negative impact sedentary behaviour and prolonged sitting have on cerebrovascular function in the child.

Text

2022-09-28

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/82776

Kinesiology

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/