Identification and modification of cardiometabolic disease risk factors in South African urban primary school children

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dc.contributor.advisorSemple, S.J.
dc.contributor.advisorMcKune, A.
dc.contributor.advisorKolanisi, U.
dc.contributor.authorvan Biljon, Anneke
dc.date.accessioned2019-10-01T10:14:31Z
dc.date.available2019-10-01T10:14:31Z
dc.date.issued2018
dc.descriptionThesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy in Human Movement Science (Kinderkinetics)in the Faculty of Science and Agriculture at the University of Zululand, 2018.en_US
dc.description.abstractThe initial asymptomatic process of atherosclerosis is known to develop in childhood and is associated with increases in cardiometabolic disease (CMD) risk factors. Low physical activity (PA) levels and sedentary lifestyles have been identified as contributory factors to CMD. In addition, PA levels are known to influence the function of the cardiac autonomic nervous system (ANS), and are a possible mechanism for explaining the association between insufficient PA, morbidity and mortality. Consequently, it has been proposed that sufficient PA may enhance cardiac ANS activity in children. However, there is still a lack of consensus on the exact dosage of exercise required for optimal ANS adaptation. This thesis aims to identify and modify the risk for CMD in urban primary school children. A cross-sectional study was performed to establish PA levels in South African primary school children. This was followed by a study that examined associations between individual CMD risk factors and altered ANS activity. The effect of two different exercise doses on CMD risk factors in overweight children was explored in a pilot study that lead to the quasi experimental study where the effectiveness of isocaloric exercise protocols on CMD risk factors and cardiac autonomic modulation in children were explored. Exercise interventions were set at either 65% to 70% of the maximum heart rate (MHR) in the moderate-intensity continuous training (MICT = 29) group or >80% MHR in the high-intensity interval training (HIIT = 29) group, or the interventions were combined in the alternate (ALT = 27) group. Heart rate variability (HRV) was used to measure cardiac ANS activity. Overall, we found significant discrepancies in PA levels among gender, age and ethnic groups, raising important questions about population group equality in terms of access to participate in PA. The second cross-sectional study established strong associations between individual CMD risk factors and cardiac ANS activity. Lastly, the pilot study showed different cardiometabolic effects induced by moderate-intensity and vigorous-intensity. While the quasi experimental study demonstrated that both the magnitude and components of CMD risk factors and ANS relate to exercise intensity. When the effects of these interventions were examined, enhanced vagal activity (RMSSD, pNN50, SD1) seemed to be achieved through high-intensity interval training (HIIT), when compared with moderate-intensity continuous training (MICT). In conclusion, this thesis provides evidence that HIIT induces more superior cardioprotective effects in children than does MICT. The favourable outcomes of HIIT may have important clinical implications in regards to reducing the risk of developing CMD; however, studies that implement longer terms are required to confirm the findings.en_US
dc.identifier.urihttps://hdl.handle.net/10530/1848
dc.language.isoenen_US
dc.publisherUniversity of Zululanden_US
dc.subjectcardiometabolic diseaseen_US
dc.subjectcardiac autonomic nervous system (ANS)en_US
dc.subjectCMDen_US
dc.titleIdentification and modification of cardiometabolic disease risk factors in South African urban primary school childrenen_US
dc.typeThesisen_US
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