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In the context of epidemiological transitions in Latin American countries evidence is scarce. In Colombia, despite a broad policy framework for healthy lifestyles promotion, surveillance of movement behaviours including physical activity and sedentary behaviours has been limited. Therefore, this thesis aims to: a) Describe indicators of physical activity and sedentary behaviours among Colombian children and adolescents; b) determine the factors associated with meeting physical activity guidelines, engaging in active play, using active transportation and spending excessive recreational screen time among Colombian children and adolescents; and c) draw international comparisons of physical activity and sedentary behaviour indicators. To accomplish this, cross-sectional data from the National Survey of Nutrition in Colombia 2015-2016 and the Global Matrix of Physical Activity in Children and Youth 3.0 were analyzed. This dissertation compiles five research manuscripts prepared and submitted for publication in peer-reviewed scientific journals. Paper one describes physical activity indicators and correlates among Colombian children and found that a low proportion of children and adolescents in Colombia are physically active, with a consistently lower prevalence among females across all age groups. Paper two depicts the national situation of active transportation to school, indicating a non-negligible prevalence of this behaviour and several correlates to guide the design of strategies to promote walking and biking to school in Colombia. Paper three focused on recreational screen time and its correlates and found a high prevalence of excessive recreational screen time that increases with age. Paper four puts Colombian data in global context with nine other countries with a similar human development index participating in the Global Matrix 3.0 initiative. This study compared grades of behavioural and sources of influence indicators and found similarly low performance across countries. In paper five a latent profile analysis approach was used to build active transportation profiles that contribute to understand active commuting to school across 49 countries from the Global Matrix 3.0. This dissertation helps fill gaps in knowledge in Colombia, and middle-income countries more broadly, providing national estimates of physical activity and sedentary behaviours of children aged 3-17 years for the first time in the surveillance history of the country.

Prolonged time sitting has been linked to an increased risk of cardiovascular diseases (CVD), cardiovascular mortality (CVM), all-cause mortality, diabetes and some cancers. Workers in occupations where there is no alternative to sitting can best be defined as compulsory sedentary workers , which involve bus and lorry drivers amongst others. Limited research is available on the health behaviours and health profiles of individuals working within these occupations. This thesis adopts a mixed methods approach and fits within the MRC framework for the development of complex interventions to specifically investigate bus and lorry drivers sedentary behaviours and physical activity levels in association with their cardiovascular health. Chapter 3 describes a pilot study, which results showed bus drivers accumulate 12 hours sitting on workdays and presented higher than the recommended ranges for BMI, body fat, waist circumference and blood pressure. Chapter 4 explores the validity of using an ActiGraph accelerometer compared to the activPAL to assess bus drivers sedentary behaviours. Results highlight that compared to the activPAL, the ActiGraph underestimates sedentary time during workdays (151minutes/day) and working hours (172min/day). Chapter 5 phenotypes UK lorry drivers sedentary behaviours and non-sedentary behaviours during workdays and non-workdays and examines lorry drivers markers of cardiovascular health. Lorry drivers accumulate 13 hours sitting on workdays and 8 hours on non-workdays and presented an ill-cardiovascular profile. Chapter 6 examines the effects of an intervention designed to promote PA and reduce sedentary time on a range of cardiovascular risk factors in a sample of lorry drivers. Chapter 7 presents a process evaluation of the Structured Health Intervention for Truckers (SHIFT) programme described in Chapter 6. This thesis highlights that bus and lorry drivers accumulate the highest amount of sitting time reported up to date, together with high levels of physical inactivity and an ill-cardiovascular profile. However, positive changes in cardiovascular risk factors were observed when drivers increased their daily average of step counts. Overall, these results emphasise that targeting bus and lorry drivers health behaviours should be a public health priority.

In recent years, physical activity and fitness transitions, described as declines in physical activity and aerobic fitness, coupled with increased sedentary behaviour, have been observed among school-aged children. Consequently, the prevalence of childhood overweight/obesity has also increased considerably. While there is a wealth of evidence supporting such behavioural transitions in higher income countries, there exists a paucity of data on the situation in lower income countries, such as those in Sub-Saharan Africa (SSA). The premise of this thesis was to investigate the robustness of these relationships in other global regions. The first objective was to investigate the evidence for an overweight/obesity, physical activity, and fitness transition among SSA’s school-aged children. Systematic review methodology was used to examine temporal trends and correlates of overweight/obesity, physical activity, fitness, and sedentary behaviour in apparently healthy or population based samples of children (5 - 17 years). The second objective of this thesis was to determine the prevalence and correlates of overweight/obesity and physical activity among Kenyan children aged 9 to 11 years, having contextualised Kenya within the broader situation in SSA. Further, the relationships between self-reported and directly assessed measures of physical activity and sedentary time by weight status in Kenyan children were investigated. The third objective was to examine moderate-to-vigorous physical activity (MVPA) patterns accrued by time of day among Kenyan children using the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE)-Kenya data. Activity patterns in the Kenyan setting were then compared to similar ISCOLE-Canada data from Canadian children, revealing differences and similarities in the accumulation of MVPA, light physical activity, and sedentary time. Systematic review data syntheses revealed a trend towards increasing proportions of overweight/obesity among Sub-Saharan Africa’s school-aged children. Further, urbanization and higher socioeconomic status (SES) were associated with decreased physical activity and aerobic fitness, and increased sedentary behaviours and body composition measures. ISCOLE-Kenya data analyses found a prevalence of childhood overweight/obesity of 20.8% in Nairobi, with few children meeting global physical activity guidelines (12.6%). Mean daily sedentary time was 398 minutes, time spent in light physical activity was 463 minutes, and time spent in MVPA was 36 minutes. Higher SES and parental education attainment were associated with a higher likelihood of children being overweight/obese and a lower likelihood of children meeting the physical activity recommendations. Data analyses also revealed considerable discrepancies in both self-report and direct measures of physical activity by weight status, and weak to moderate correlations between self-report and direct measures of physical activity. Under/healthy weight children had significantly higher directly measured mean daily minutes of MVPA compared to overweight/obese children (39 verses 20 minutes); had lower mean weekend-day minutes of sedentary time (346 verses 365 minutes); and had a higher proportion who met physical activity guidelines (15.5% versus 2.6%). Lastly, while MVPA patterns among urban Kenyan children were largely similar to those of urban Canadian children with regard to relationships by sex, BMI category, and weekday/weekend days; in the Kenyan sample, much unlike many higher income countries, lower SES was associated with higher MVPA.

In recent years, physical activity and fitness transitions, described as declines in physical activity and aerobic fitness, coupled with increased sedentary behaviour, have been observed among school-aged children. Consequently, the prevalence of childhood overweight/obesity has also increased considerably. While there is a wealth of evidence supporting such behavioural transitions in higher income countries, there exists a paucity of data on the situation in lower income countries, such as those in Sub-Saharan Africa (SSA). The premise of this thesis was to investigate the robustness of these relationships in other global regions. The first objective was to investigate the evidence for an overweight/obesity, physical activity, and fitness transition among SSA’s school-aged children. Systematic review methodology was used to examine temporal trends and correlates of overweight/obesity, physical activity, fitness, and sedentary behaviour in apparently healthy or population based samples of children (5 - 17 years). The second objective of this thesis was to determine the prevalence and correlates of overweight/obesity and physical activity among Kenyan children aged 9 to 11 years, having contextualised Kenya within the broader situation in SSA. Further, the relationships between self-reported and directly assessed measures of physical activity and sedentary time by weight status in Kenyan children were investigated. The third objective was to examine moderate-to-vigorous physical activity (MVPA) patterns accrued by time of day among Kenyan children using the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE)-Kenya data. Activity patterns in the Kenyan setting were then compared to similar ISCOLE-Canada data from Canadian children, revealing differences and similarities in the accumulation of MVPA, light physical activity, and sedentary time. Systematic review data syntheses revealed a trend towards increasing proportions of overweight/obesity among Sub-Saharan Africa’s school-aged children. Further, urbanization and higher socioeconomic status (SES) were associated with decreased physical activity and aerobic fitness, and increased sedentary behaviours and body composition measures. ISCOLE-Kenya data analyses found a prevalence of childhood overweight/obesity of 20.8% in Nairobi, with few children meeting global physical activity guidelines (12.6%). Mean daily sedentary time was 398 minutes, time spent in light physical activity was 463 minutes, and time spent in MVPA was 36 minutes. Higher SES and parental education attainment were associated with a higher likelihood of children being overweight/obese and a lower likelihood of children meeting the physical activity recommendations. Data analyses also revealed considerable discrepancies in both self-report and direct measures of physical activity by weight status, and weak to moderate correlations between self-report and direct measures of physical activity. Under/healthy weight children had significantly higher directly measured mean daily minutes of MVPA compared to overweight/obese children (39 verses 20 minutes); had lower mean weekend-day minutes of sedentary time (346 verses 365 minutes); and had a higher proportion who met physical activity guidelines (15.5% versus 2.6%). Lastly, while MVPA patterns among urban Kenyan children were largely similar to those of urban Canadian children with regard to relationships by sex, BMI category, and weekday/weekend days; in the Kenyan sample, much unlike many higher income countries, lower SES was associated with higher MVPA.

Introduction : Seulement 7% des Canadiens de 17 ans et moins pratiquent 60 minutes d’activité physique modérée à vigoureuse quotidiennement. La majorité dépasse le temps d’écran quotidien recommandé de deux heures. Plusieurs études transversales indiquent que les deux comportements évoluent indépendamment et ne seraient que faiblement corrélés. Objectifs et hypothèses : Les objectifs de ce mémoire est d’identifier des trajectoires d’activité physique et des trajectoires de temps devant l’écran durant l’adolescence, par sexe, et de décrire la distribution des individus selon l’appartenance simultanée aux deux trajectoires. Nos hypothèses stipulent que des trajectoires différentes seront observées pour les deux sexes et que les deux comportements ne s’influenceront pas. Méthodes : Les données proviennent d’une étude prospective de 1294 adolescents de la région de Montréal, recrutés en 1999 à l’âge de 12-13 ans. Des questionnaires ont été remplis en classe à chaque 3 mois, de la première à la cinquième année du secondaire. Des modélisations de trajectoires de groupe ont identifié des trajectoires d’activité physique et de temps devant l’écran. Une modélisation de trajectoires jointes a rapporté des probabilités d’appartenance aux trajectoires des deux variables. Résultats : Cinq groupes ont été identifiés pour les trajectoires d’activité physique pour les deux sexes. Quatre groupes ont été identifiés pour les garçons et 5 pour les filles concernant le temps passé devant l’écran. 57% des garçons et 46% des filles ont fait des activités physiques pendant 6-7 jours par semaine, durant toute l’adolescence. Toutes les trajectoires de temps devant l’écran accumulent plus de deux heures d’écran quotidiennement. Les probabilités conditionnelles suggèrent une relation entre l’activité physique et le temps devant l’écran. Conclusion : Le développement de l’activité physique et du temps devant l’écran est hétérogène durant l’adolescence. Leur coévolution doit être prise en compte par les professionnels en santé publique. / Introduction: Only 7% of Canadians age ≤ 17 years engage in the recommended 60 minutes or more of moderate-to-vigorous physical activity (PA) daily. Further, most youth surpass the recommended screen time maximum of 2-hours daily. Many cross-sectional studies suggest that PA and screen time are only weakly correlated and that they evolve independently. Objectives and hypotheses: The first objective of this MSc thesis was to model PA and screen time trajectories during adolescence, in boys and girls. The second objective was to describe the distribution of participants according to concurrent membership in the two sets of trajectories. Our hypotheses were that trajectories differ by sex and that PA trajectories are independent of screen time trajectories. Methods: Data were drawn from an ongoing longitudinal study of 1294 adolescents age 12-13 years recruited in 1999-2000 in 10 Montreal-area high schools. Self-report questionnaires were completed during class time, every 3 months from grade 7 to 11. Group-based trajectory modeling identified PA and screen time trajectories. Joint trajectory models provided membership probabilities in both PA and screen time trajectories. Results: Five groups of PA trajectories were identified in both sexes. Four and five screen time trajectory groups were identified in boys and girls, respectively. Half (57%) of boys and 46% of girls engaged in PA 6-7 days weekly during the entire 5-year follow-up. All screen time trajectories were above the recommended 2-hours daily. Conditional probabilities suggested weak associations between PA and screen time. Conclusion: Patterns of PA and screen time are heterogeneous during adolescence. Their co- evolution may need to be considered by public health practitioners.

Contexte: La dépression chez les jeunes est un problème de la santé publique croissant. L’activité physique (AP), les comportements sédentaires (CS) et le sommeil représentent des facteurs de risque modifiables des symptômes dépressifs. La compréhension de comment le temps passé quotidiennement dans l'ensemble de l'AP, des CS et du sommeil est associée aux symptômes dépressifs peut éclairer les interventions qui aident à prévenir les symptômes dépressifs chez les jeunes adultes. Objectifs: Ce mémoire vise à estimer l'association entre la proportion de temps sur une période de 24 heures alloué à l’AP d’intensité modérée à vigoureuse (APMV), la marche, les CS et le sommeil, et les symptômes dépressifs chez les jeunes adultes. Il vise à estimer le changement des symptômes dépressifs avec la réaffectation du temps entre les comportements. Méthodes: Les données de l'étude Nicotine Dependence in Teens (NDIT), une étude longitudinale en cours qui a recruté 1294 élèves de 7e année dans 10 écoles secondaires à Montréal, au Canada, ont été utilisées. Les données pour ce projet ont été collectées à 20 et 24 ans à l'aide de questionnaires auto-rapportés. Une analyse compositionnelle a été effectuée. La taille de l'effet de l'association a été estimée par un modèle de réaffectation du temps. Résultats: Aucune association statistiquement significative a été observée entre les proportions de temps passé en APMV (p = 0,273), la marche (p = 0,861), le CS (p = 0,723) et le sommeil (p = 0,948) et les symptômes dépressifs chez les jeunes adultes. La réaffectation de 15 minutes d’APMV aux CS est associée à une augmentation de 3% des symptômes dépressifs. La réaffectation de 15 minutes de CS à l’APMV est associée à une réduction de 1% des symptômes dépressifs. Cependant, ces changements étaient également non significatifs. Conclusion: Le temps alloué à l'APMV, la marche, les CS et le sommeil n’étaient pas associés aux symptômes dépressifs chez les jeunes adultes. La réaffectation du temps entre les comportements de mouvement a entraîné des changements non significatifs des symptômes dépressifs. Ces résultats devront être vérifier avant de formuler des recommandations. / Background: Depression among youth is a growing public health burden. Physical activity (PA), sedentary behaviours (SB) and sleep are modifiable risk factors for depressive symptoms. Understanding how the interplay between the mix of time spent in daily in all of PA, SB and sleep is associated with depressive symptoms may inform interventions that help prevent depressive symptoms in young adults Objectives: This thesis aims to estimate the association between the proportion of time spent during a 24-hour period in each of moderate-to-vigorous intensity PA (MVPA), walking, SB and sleep, and depressive symptoms in young adults. It also aims to estimate change in depressive symptoms with the reallocation of time across movement behaviours. Methods: Data were drawn from the Nicotine Dependence in Teens (NDIT) study, an ongoing longitudinal study that recruited 1294 7th grade students in 10 secondary schools in Montreal, Canada. Data were collected using self-report questionnaires at ages 20 and 24. PA, SB and sleep were analyzed using time-use compositional analysis. Effect size of the association was estimated using a compositional time reallocation model. Results: There was no statistically significant association between the proportion of time spent in MVPA (p=0.273),walking (p=0.861), SB (p=0.723) or sleep (p=0.948) and depressive symptoms in young adults. There was 3% increase in depressive symptoms with reallocation of 15 minutes from MVPA to SB and 1% reduction in depressive symptoms with reallocation of 15 minutes from SB to MVPA. However, these changes were similarly non-significant Conclusion: Time-use in MVPA, walking, SB and sleep overall was not associated with depressive symptoms in young adults in our study. Reallocating time between movement behaviours resulted in minimal non-significant changes in depressive symptoms. Replication is needed before our findings can be translated to recommendations.