Physical activity in childhood and adolescence : health benefits and environmental determinants

Abstract

Background: Physical inactivity is associated with higher risk of various diseases, but how physical activity (PA) can improve the well-being of youth in the community remains uncertain. According to socio-ecological model, PA is influenced by multilevel factors, but the role of school PA environment and socioeconomic status remains elusive. Objective: A series of studies were conducted to: (1) study the impact of PA on youth’s mental health and its potential mechanism (2) develop a community-based PA intervention model and evaluate its effectiveness on improving well-being, (3) examine the existence of any socioeconomic disparity in PA levels and its associated risk on obesity and hypertension, and (4) explore the relationship between school PA environment and childhood obesity. Methods: Objectives 1, 3, and 4 were investigated using cross-sectional epidemiological studies. Objective 2 was examined using a sequential study design. First, a formative mixed-mode study was conducted to examine the adolescents’, parents’ and teachers’ perceived barriers of PA to guide the design of a sports mentorship intervention model. Next, a randomised controlled trial was implemented. Physical and mental health outcomes were measured using self-completed health-related quality-of-life surveys, direct physical fitness tests, and standardized measurements on the youth’s blood pressure and growth parameters. Results: Objective 1 identified resilience, a psychological asset of adolescents, as the only significant mediator (proportion of mediation=60%) between PA and mental health. The formative part of Objective 2 identified competing activity and incorrect perception as the most significant barriers for PA intervention. Based on these findings, a sports mentorship programme was developed. The intervention lasted for one academic year and consisted of 18 weekly 90-minute sessions of sports for exercise and skill building. The programme was also designed to promote resilience and motivation. Intention-to-treat analysis showed significant benefits for mental well-being (Cohen’s d 0.25, p=0.001), self-efficacy (0.22, p=0.01), resilience (0.19, p=0.02), and physical fitness (0.18–28, p<0.03). Subgroup analysis showed significant reductions in fat composition among inactive students. Objective 3 identified six school PA factors that were associated with a lower risk of obesity, namely school campus size (risk ratio 0.93, p=0.02), number of PA facilities (0.87, p<0.001), PE teacher’s experience (0.93, p<0.001), perceived benefits of PA (0.96, p=0.02), school PA ethos (0.91, p<0.001), and number of PA programmes (0.93, p<0.001). A school with at least three protective factors had much lower risk of obesity (0.68, p<0.001). Lastly, Objective 4 revealed both family and neighbourhood socioeconomic statuses were associated with physical inactivity. Lower SES status was associated with childhood obesity and hypertension. Conclusions: This study supported the benefits of PA on the mental health and physical fitness of youth and identified resilience as a potential mediator. The newly developed sports mentorship programme appears to be a promising model to improve the physical and mental health of adolescents. Adding to the socio-ecological model, this study identified the school PA environment and socioeconomic status were important correlates to PA and health. The findings can help to guide development of more effective anti-obesity programme and other school-based health interventions in the future.