Williams, Craig ABarker, Alan RAlkhraiji, Mohummed Hamad2023-06-122023-06-122022https://hdl.handle.net/20.500.14154/68355Physical activity in the form of moderate-to-vigorous physical activity (MVPA), sedentary behaviour in the form of recreational screen time (ST), and sleep, are individually associated with cardiovascular disease (CVD) risk factors in adolescents. Commonly, researchers investigate these three movement behaviours in relation to CVD risk factors in isolation. However, after the launch of the Canadian 24-Hour Movement Guidelines for children and youth, there have been calls to integrate all three 24-hour behaviours (PA, ST, & sleep). Furthermore, a scientific statement from the American Heart Association highlights the importance of cardiorespiratory fitness (CRF) as a measurement for health screening in children and adolescents as CRF is a strong predictor of CVD risk. Previous studies have individually explored how the 24-hour movement guidelines or CRF are associated with CVD risk factors in adolescents; however, which of the two (24-hour movement guidelines or CRF) is more strongly associated with CVD risk factors in adolescents is unknown. Currently, most studies have been conducted in North America and Europe, with the Middle East neglected, including Saudi Arabia, which has a very different lifestyle, environment, climate, school system, and culture compared to North America and Europe. Therefore, to address this gap in the literature in the context of Saudi Arabia, the studies included in this thesis aimed to investigate the prevalence of 24-hour movement guidelines and CRF and their relationship with CVD risk factors in adolescents from Saudi Arabia aged 12–15 years old. Chapter 4 narratively reviewed movement guidelines and CRF in relation to CVD risk factors in children and adolescents from the Gulf Cooperation Council Countries, which indicated gaps in the literature investigating the 24-hour movement guidelines. In addition, Chapter 4 highlighted that there is poor evidence for an association between single movement guidelines and CRF with multiple CVD risk factors; most studies have only examined associations with weight status. Chapter 5 examined the reliability and validity of using the Global School-Based Student Health Survey (GSHS) to assess the 24-hour movement guidelines in (n = 120; 50% females) adolescents aged 12–15 years old, from Saudi Arabia and found acceptable reliability and validity. In Chapter 6, the GSHS was used to examine the prevalence of the 24-hour movement guidelines and their associations with overweight/obesity in a sample of (n = 4224; 52% females) participants aged 12–15 years old. The results indicated that only 2.7% achieved the recommended 24-hour movement guidelines and highlighted weak, non-significant associations with the risk of overweight/obesity. In Chapter 7 a subsample of (n = 120; 50% females) participants aged 12–15 years old from the study in Chapter 6 underwent a 24-hour movement guidelines assessment using GENEActiv accelerometers (for MVPA and sleep) and the GSHS (for ST). In addition, CRF was assessed using the Progressive Aerobic Cardiovascular Endurance Run test, and fasting blood samples, blood pressure, and anthropometrics were collected. None of the adolescents in this subsample met all three of the 24-hour movement guidelines, and there were no favourable significant associations with individual or clustered CVD risk factors. In addition, few males (16%) and almost half of the female (46.3%) participants had a healthy CRF. However, in males only, having a CRF was significantly and negatively associated with waist circumference (WC) and clustered CVD risk. Collectively, the results presented in this PhD thesis contribute to enhancing the literature in four ways. Firstly, it demonstrates that there is a lack of studies on the 24-hour movement guidelines and CRF in relation to CVD risk factors for adolescents from the Gulf Cooperation Council countries. Secondly, it is the first study to examine a questionnaire for its reliability and validity to measure the 24-hour movement guidelines, which found an acceptable reliability and validity. Thirdly, it shows that via a questionnaire few adolescents (2.7%) from Saudi Arabia are meeting the 24-hour movement guidelines, which is not significantly associated with being at risk of overweight/obesity. Lastly, it shows that when using device-based accelerometry, none of the adolescents from Saudi Arabia are meeting the 24-hour movement guidelines, which is not significantly associated with individual or clustered CVD risk factors profiles in both sexes. Moreover, healthy CRF was not significantly associated with individual or clustered CVD risk factors in females, while in males, healthy CRF was only significantly and inversely associated with WC and clustered CVD risk factors. Based on the above findings, it is suggested that 24-hour movement guidelines are not favourable strongly associated with individual or clustered CVD risk factors in adolescents of both sexes from Saudi Arabia. In addition, in females it appears that there are no significant associations between CRF and individual or clustered CVD risk factors. Initiatives should be developed to encourage male adolescents from Saudi Arabia aged 12–15 years old to achieve a healthy CRF to reduce the risk of WC and clustered CVD risk factors. However, future longitudinal studies with larger sample sizes would enable further insight into the associations between 24-hour movement guidelines and CRF in relation to CVD risk factors in adolescents from Saudi Arabia and should provide specific recommendations for both sexes.315enepidemiologycardiovascular diseaseschool childrenphysical fitnessphysical activitysleepsedentary timeThesis