The health impact of sedentary behaviour in children and youth

Abstract

Emerging evidence suggests that sedentary behaviour is independently associated with cardiometabolic disease risk in school-aged children and youth. This thesis includes 4 related studies in the pursuit of 2 objectives: 1) To determine the cross-sectional association of sedentary time, interruptions in sedentary time, sedentary bout length, and total movement variability with markers of cardiometabolic disease risk among children and youth, and 2) To examine the impact of 1-day of prolonged sedentary behaviour, with and without interruptions or structured physical activity, on markers of cardiometabolic disease risk, hunger, food intake and spontaneous physical activity levels in children and youth. In Study 1, we found that interruptions in sedentary time and short bouts of sedentary time were beneficially associated with clustered cardiometabolic disease risk in boys and girls aged 8-11 years, independent of total sedentary time, moderate-and-vigorous physical activity (MVPA), and other confounders (all p<0.05), while the opposite was true for screen based sedentary behaviours. In Study 2, we found that movement variability (minute-to-minute changes in movement intensity) was negatively associated with clustered cardiometabolic disease risk and systolic blood pressure independent of MVPA, sedentary time and other covariates in a representative sample of American children and youth aged 12-17 years (all p<0.05). In Studies 3 and 4, we found that prolonged sitting, with or without interruptions and structured MVPA did not result in acute changes in markers of cardiometabolic disease risk, nor subsequent ad libitum food intake or physical activity levels in healthy children aged 10-14 years (all p ≥0.05). Taken together, the studies that make up this thesis suggest that optimal levels of cardiometabolic disease risk are most likely to be seen in children who limit their time engaging in screen-based sedentary behaviours, who frequently interrupt their sedentary time, and who have high levels of variability in their movement behaviours.iii ContributionsThe work in this thesis is my own, and I take full responsibility for its contents. Ethics applications were required for Studies 1, 3 and 4, and details of ethics approval are provided in Appendix A. A list of co-authors from the studies that make up this thesis can be found below.

Associations between mother's and children's moderate-to-vigorous physical activity and sedentary time in the family context

“…Nonetheless, reports show that a large proportion of children do not meet current PA guidelines (i.e., at least 60 min of PA daily ( U.S. Department of Health and Human Services, 2008 )) ( Kann et al, 2016 , Chung et al, 2012 , Song et al, 2013 ). Relatedly, sedentary time (ST) is independently associated with negative health outcomes such as obesity and cardiometabolic risk ( Saunders, 2014 , Tremblay et al, 2011 ) and although there are no formal guidelines for ST in children, evidence shows that ST increases in youth as they get older: ( Janssen et al, 2016 , Pearson et al, 2017 ) Youth at age 7 years average just over 50% of their waking hours in sedentary behaviors, with that amount increasing to over 75% of the waking day in youth aged 15 years. Thus, improved methods for enhancing PA and limiting sedentary behaviors in children are needed, and implementing such methods while children are still young will have long-term benefits.…”

Preparing physically educated citizens in physical education. Expectations and practices (Preparar ciudadanos fisicamente bien educados en Educación Física. Expectativas y prácticas)

“…This has likely contributed to the growing attention paid worldwide to the number of people who are not active 2017, Retos, 31, 245-251 © Copyright: Federación Española de Asociaciones de Docentes de Educación Física (FEADEF) ISSN: Edición impresa: 1579-1726. Edición Web: 1988-2041 enough, whatever their age, gender or socioeconomic status (WHO, 2016), and to the place of sedentariness in daily life (Saunders, 2014;SBRN, 2012).…”

Perceptions and Practices of Physical Activity Among Colombian Overweight/Obese Schoolchildren

“…Although PA plays an important role in weight management, children are not meeting the recommended levels of PA (Moore et al, 2010) and are more likely to engage in sedentary behaviors along with a high consumption of energy-dense food and drinks (Hale & Guan, 2015; Saunders, 2014; Tremblay et al, 2011). Although physical education (PE) programs aim to promote PA and reach most school-aged youth, PA levels within PE lessons are often low (Lonsdale et al, 2013).…”