Does it fit better? Measures of physical activity among adolescents in relation to health indicators.

BACKGROUND: Measuring physical activity (PA) is one of the pillars of successful health promotion; however, we struggle to find a tool enabling the identification of risk groups. The current standard approach of assessing moderate-to-vigorous physical activity (MVPA) every day does this inadequately. The aim of this study is to explore whether three other indicators of adolescents' PA can identify such risk groups in a better way. METHODS: We used data on 888 11- to 15-year-old adolescents (mean age = 13.5, 56% boys) from the Health Behaviour in School-aged Children study conducted in 2018 in Slovakia. Sufficient PA was indicated by the following four indicators: (i) MVPA every day, (ii) MVPA 5-7 days a week, (iii) engagement in organized sports (team or individual) and (iv) combining MVPA 5-7 days a week and engagement in organized sports. We used binary logistic regression analysis to assess the association of various indicators of adolescents' PA with body composition, cardiovascular fitness and self-rated health (SRH), considering age and gender. RESULTS: Being active based on various indicators was associated with better health outcomes, with the strongest associations for the indicator combining MVPA 5-7 days a week and engagement in organized sports. The only exceptions were the non-significant associations of active adolescents (being active 5-7 days per week or engaged in organized sports) with cardiovascular fitness and SRH. CONCLUSIONS: Measuring PA using an indicator that combines MVPA 5-7 days a week and engagement in organized sports is the most valid using three health indicators as criteria.

Body image, body composition and environment: do they affect adolescents' physical activity?

BACKGROUND: Most adolescents are less physically active than recommended, despite the strong effort of various stakeholders to promote physical activity (PA). Body image and body composition may play an important role not only in directly facilitating adolescents' PA but also in enabling environment-related factors. As evidence is lacking, we aimed to assess the associations of adolescents' PA with body-related and environment-related factors, whether this differs by age and gender, and whether these factors interact. METHODS: We used data on 888 11- to 15-year-old adolescents (mean age = 13.5, 56% boys) from the Health Behaviour in School-aged Children study conducted in 2018 in Slovakia. We used multinomial logistic regression analysis to assess the association of adolescents' PA with body-related factors (body image, body composition) and environment-related factors (PA-promoting environment, less leisure constraints), taking into account age and gender. RESULTS: Adolescents who perceived their body as not too fat were more likely to be physically very active rather than inactive [odds ratios (ORs)/95% confidence interval (CI) 2.15/1.44-3.22], and similarly those who were not overweight/obese (3.24/2.09-5.01) and perceived less leisure constraints (1.74/1.44-2.11). In older adolescents and in girls, the association of adolescents' PA with body composition and environment-related factors was stronger. The association of adolescents' PA with perceiving less leisure constraints was stronger among adolescents who did not perceive their body as too fat (OR/95% CI 1.98/1.26-3.14), and for those who were not overweight/obese (OR/95% CI 1.62/1.01-2.57). CONCLUSION: Adolescents' PA is associated with both body-related and environment-related factors. These associations are stronger in girls and older adolescents, if co-occurring.

Barriers and enablers for sufficient moderate-to-vigorous physical activity: The perspective of adolescents.

BACKGROUND: Interventions to improve physical activity (PA) among adolescents continue to be a public health priority. To promote PA more effectively, we need to identify the main factors contributing to (not) engagement in PA in the perspective of adolescents themselves. Thus, we explored the barriers and enablers for sufficient moderate-to-vigorous physical activity (MVPA) in adolescents from their point of view. METHODS: We used qualitative data collected as part of the international Health Behaviour in School-Aged Children study. We obtained data from 14-17 years old adolescents from the first year of Slovak high school. We conducted 11 online, semi-structured individual and group interviews with 24 participants in total (7 boys; mean age = 15.17, SD = 0.87) in Slovakia. We analysed the data using consensual qualitative research and thematic analysis. RESULTS: In the statements of adolescents, four main themes were identified regarding factors contributing to (not) engagement in PA among adolescents. 'Myself as a source' represents the importance of adolescents' own efforts, knowledge, physical predispositions and PA experience. 'How PA can be done' represents school as an opportunity for PA, and PA teachers and sports coaches as specialists who can create an enabling environment for sports. 'Others as a source' represents the social circle that can set a positive sports example and can encourage adolescent's efforts in PA. 'Factors outside' represents other factors that can inspire adolescents, e.g. by giving them a comfortable space and time to exercise, or can be a barrier to PA. CONCLUSION: The potential factors that include adolescents' perspectives can be more leveraged in designing supportive, inclusive, enjoyable, and skills-appropriate PA programmes.

Are adolescents' physical activity and body-related factors associated with medically attended injuries?

Background: Injuries are the major cause of disability and death during adolescence, representing a significant public health burden among youth. Body-related factors such as body composition and cardiovascular fitness (CVF) may affect adolescents' vulnerability to injuries. As evidence is lacking, we aimed to explore the associations of medically attended injuries with adolescents' physical activity (PA) and body-related factors, and whether these associations are modified by age, gender and family affluence. Methods: We used data on 888 11- to 15-year-old adolescents (mean age = 13.5, 56% boys) from the Health Behaviour in School-aged Children study conducted in 2018 in Slovakia. We used binary logistic regression analysis to assess the association of medically attended injuries with adolescents' PA and body-related factors (body composition, CVF), considering age, gender and family affluence. Results: Adolescents were more likely to report medically attended injuries if they were physically very active (odds ratio/confidence interval OR/CI:2.76/1.83-4.15) or active (OR/CI:1.91/1.27-2.87) rather than inactive. Body-related factors were not associated with medically attended injuries among adolescents. Moreover, age, gender and family affluence did not modify the association of medically attended injuries with adolescents' PA and body-related factors. The only exception was the modifying effect of gender: the association of medically attended injuries with being very active was stronger in boys (OR/CI: 3.04/1.32-6.99). Conclusion: Very physically active adolescent boys are the most vulnerable group of adolescents in terms of injuries. PA promotion programmes should further consider gender-specific strategies aimed at preventing injuries.

Is BMI a Valid Indicator of Overweight and Obesity for Adolescents?

Background: Overweight and obesity are mostly monitored via the Body Mass Index (BMI), based on self-reported or measured height and weight. Previous studies have shown that BMI as a measure of obesity can introduce important misclassification problems. The aim of this study was to assess the validity of overweight and obesity classification based on self-reported and on measured height and weight versus the proportion of body fat as the criterion. Methods: We used data on 782 adolescents (mean age = 13.5, 55.8% boys) from the Health Behaviour in School-Aged Children (HBSC) study conducted in 2018 in Slovakia. We obtained self-reported (height and weight) and objective measures (height, weight) and the proportion of fat (as the criterion measure) measured via bioimpedance body composition analysis (BIA) with an InBody 230 from the adolescents. Results: Both measured and self-reported BMI indicated overweight and obesity with relatively low sensitivity (66-82%), but high specificity (90-92%). The superior accuracy of measured BMI in comparison to self-reported BMI was confirmed by the area under the curve (AUC) based on the receiver operating characteristics (ROC) curves (AUC measured/self-reported: 0.94/0.89; p < 0.001). The misclassification of overweight and obesity was significantly higher when using self-reported BMI than when using measured BMI. Conclusion: Both self-reported and measured BMI as indicators of overweight and obesity underestimate the prevalence of adolescents with overweight and obesity.