Correlates of Active School Transportation During the COVID-19 Pandemic Among Canadian 7- to 12-Year-Olds: A National Study.

BACKGROUND: Active school transportation (AST) is an important source of physical activity for children and a potentially important climate change mitigation strategy. However, few studies have examined factors associated with AST in the context of the COVID-19 pandemic. METHODS: We used baseline data from a longitudinal survey to investigate correlates of AST during the second wave of COVID-19 (December 2020). We collected survey data from 2291 parents of 7- to 12-year-olds across Canada and linked this information with data on neighborhood walkability and weather from national databases. We assessed potential correlates representing multiple levels of influence of the social-ecological model. We used gender-stratified binary logistic regression models to determine the correlates of children's travel mode to/from school (dichotomized as active vs motorized), while controlling for household income. We examined the correlates of travel mode for both the morning and afternoon trips. RESULTS: Consistent correlates of AST among Canadian children during the COVID-19 pandemic included greater independent mobility, warmer outdoor temperature, having a parent who actively commuted to work or school, living in a household owning fewer vehicles, and living in a more walkable neighborhood. These findings were largely consistent between boys and girls and between morning and afternoon school trips. CONCLUSIONS: Policymakers, urban planners, and public health workers aiming to promote AST should focus on these correlates while ensuring that neighborhoods are safe for children. Future research should monitor the prevalence and correlates of AST as COVID-19 restrictions are removed.

Children's Independent Mobility, School Travel, and the Surrounding Neighborhood.

INTRODUCTION: Children's active travel to and from school (AST) and children's independent mobility (CIM) are consistently positively associated with physical activity (PA); however, few researchers have investigated associations between objective measures of the environment and indicators of AST and CIM in national samples. METHODS: A national sample of 2,067 Canadian parents of 7- to 12-year-old children was recruited in December 2020. Regression analyses were used in 2023 to assess the association between geographic information system measures of park density, blue space, population density, greenspace, intersection density, and CIM and AST to and from school. RESULTS: Children in areas with high versus low park density (>0.025 vs. ≤0.025) had higher odds of travel to school via active modes (OR: 1.47 [1.14, 1.91], p=0.003). Children in neighborhoods in the highest quartile for neighborhood greenspace (Normalized Difference Vegetation Index) were more likely to travel to home actively than those in areas of lower greenspace (OR: 1.70 [1.18, 2.45], p=0.004). On average, children living in areas in the highest versus the lowest quartile for intersection density were more likely to engage in AST to (OR: 2.43 [1.58, 3.75], p<0.001) and from (OR: 2.77 [1.80, 4.29], p<0.001) school. CONCLUSIONS: The observed associations underscore a need for city planners and policymakers to ensure sufficient access to parks and neighborhood greenspace, especially if findings are confirmed in longitudinal studies. More research is needed to investigate the role of intersection density in supporting AST and CIM.

Canadian children's independent mobility during the COVID-19 pandemic: A national survey.

Independent mobility (IM) is associated with children's physical activity and indicators of social, motor, and cognitive development. We surveyed Canadian parents of 7- to 12-year-olds (n = 2291) about social-ecological correlates of IM in the second wave of COVID-19 (December 2020). We used multi-variable linear regression models to identify correlates of children's IM. Our final model (R2 = 0.353) included four individual-, eight family-, two social environment- and two built environment-level variables. The correlates of boys' and girls' IM were similar. Our findings suggest that interventions to support children's IM in a pandemic context should target multiple levels of influence.

Appearance satisfaction mediates the relationship between recreational screen time and depressive symptoms in adolescents.

BACKGROUND: Research suggests there is an association between high levels of recreational screen time and depression among adolescents; however, mechanisms driving this association remain unknown. The present study examined appearance and weight satisfaction and disordered eating behaviors as mediators in the relationship between recreational screen time and depressive symptoms in adolescents. METHOD: Longitudinal data on screen time, depressive symptoms, disordered eating behaviors, and appearance and weight satisfaction from 304 adolescents (194 females, Mage = 13.40) were analyzed through a moment structure model. RESULTS: Results revealed appearance dissatisfaction mediated the direct effect of recreational screen time on depressive symptoms (Estimate = 0.48, SE = .18, 95% CI [0.12, 0.84]), and that recreational screen time was significantly related to lower appearance satisfaction (Estimate = -0.06, SE = .02, 95% CI [-0.10, -0.01]), which was significantly predictive of more severe depressive symptoms (Estimate = -1.49, SE = .62, 95% CI [-2.71, -0.28]). CONCLUSIONS: These findings suggest that modulating screen time may be an efficacious strategy to reduce appearance dissatisfaction and depressive symptoms during adolescence.

Associations between physical activity motives and trends in moderate-to-Vigorous physical activity among adolescents over five years.

This study examined the longitudinal associations between five physical activity (PA) motives and moderate-to-vigorous PA (MVPA) across a 5-year period spanning late childhood to middle adolescence.METHODS: Data (n = 937; 55% girls; mean age = 10.33 years) were drawn from the Monitoring Activities for Teenagers to Comprehend their Habits study. PA motives and MVPA were assessed 15 times over the course of 5 years. Measurement invariance for the Motives for Physical Activity Measure-Revised (MPAM-R) questionnaire was established, and sex-stratified mixed-effects regression models were analysed.MVPA increased until a mean age of 12.18 years for girls and 12.89 years for boys before decreasing through the final assessment. From late childhood to middle adolescence, for boys, enjoyment motives were positively (ß(95% CI) = 6.14(3.86-8.43)), while fitness motives were negatively (ß(95% CI) = -4.80(-8.0, -1.59)) associated with MVPA. Whereas, for girls, competence motives were positively ß(95% CI) = 3.44(1.59-5.28)) associated with MVPABoys may benefit from PA interventions, if these were primarily aimed at increasing ones' enjoyment, whereas developing a girl's competence may provide greater contributions to a girl's future PA behaviours. PA interventions should avoid promoting the desire to be active to improve fitness, particularly among boys.

Examining the Bidirectional Association Between Body Esteem and Body Mass Index During Adolescence.

OBJECTIVE: Research on body esteem (weight and appearance esteem) and weight suggests that having a positive body esteem may be associated with more stable weight trajectories during adolescence, and adolescents with higher weight report lower levels of body esteem. However, bidirectional relationships between body esteem and weight have not yet been examined. This 3-year longitudinal study examined (1) bidirectional relationships between body esteem and body mass index (BMI) and (2) how BMI and body esteem changed together throughout adolescence. METHODS: Participants (N = 1163 adolescents, at time 1 [T1] baseline; 60.3% female) from a school-based community sample completed surveys approximately annually for 3 years. RESULTS: Latent growth modeling revealed that (a) among boys and girls, appearance and weight esteem scores decreased over time, (b) higher initial BMI scores were associated with slower decreases in appearance esteem over time. However, evidence for bidirectionality was not found, in which baseline appearance and weight esteem did not predict changes in BMI over time and vice versa. CONCLUSION: Results suggest that changes in BMI and body esteem are co-occurring (rather than predictive) throughout adolescence. The decreasing trajectory of body esteem over time suggests the need for prevention efforts to improve body esteem throughout adolescence.

One size does not fit all: identifying clusters of physical activity, screen time, and sleep behaviour co-development from childhood to adolescence.

PURPOSE: Canada was the first to adopt comprehensive 24-h movement guidelines that include recommendations for physical activity, screen time and sleep to promote health benefits. No studies have investigated the concurrent development of these behaviours in youth. The objectives were to assess adherence to the Canadian 24-h movement guidelines for children and youth and estimate co-development of self-reported moderate-to-vigorous intensity physical activity (MVPA), screen time and sleep during 8-years from childhood to adolescence. METHODS: Nine hundred and twenty three participants of the MATCH study self-reported their MVPA, screen time and sleep duration at least twice over 8 years. MVPA and screen time were measured three times per year (24 cycles), and sleep was measured once per year (8 cycles). Guideline adherence was dichotomised as meeting each specific health behaviour recommendation or not. Multi-group trajectory modeling was used to identify unique trajectories of behavioural co-development. Analyses were stratified by sex. RESULTS: Between 10 and 39% of youth did not meet any recommendation at the various cycles of data collection. More than half of youth met only one or two recommendation, and roughly 5% of participants met all three recommendations at one or more study cycle throughout the 8 years of follow-up. Four different trajectories of behavioural co-development were identified for boys and for girls. For boys and girls, a complier (good adherence to the guideline recommendations; 12% boys and 9% girls), a decliner (decreasing adherence to the guideline recommendations; 23% boys and 18% girls) and a non-complier group (low adherence to the guideline recommendations; 42% boys and 42% girls) were identified. In boys, a MVPA-complier group (high MVPA-low screen time; 23%) was identified, whereas in girls a screen-complier group (moderate screen time-low MVPA; 30%) was identified. CONCLUSIONS: There is a need to recognise that variations from general trends of decreasing MVPA, increasing screen time and decreasing sleep exist. Specifically, we found that although it is uncommon for youth to adhere to the Canadian 24-h movement guidelines, some youth displayed a high likelihood of attaining one or multiple of the behavioural recommendations. Further, patterns of adherence to the guidelines can differ across different sub-groups of youth.

Physical activity mediates the relationship between outdoor time and mental health.

Both spending time outdoors and participating in physical activity improve mental health. Given that the outdoor environment provides an ideal location for physical activity, better understanding of the relationships among time spent outdoors, physical activity and positive mental health is needed to help guide interventions. The aim was to examine if physical activity moderates or mediates the relationship between outdoor time and positive mental health. Two-hundred-forty-two participants (15 ±â€¯1 years old, 59% girls) from New Brunswick, Canada were included in the current analysis. Youth self-reported time spent outdoors and moderate-to-vigorous physical activity (MVPA) three times between October 2016 and June 2017. Data on their mental health were collected in October 2017. Values of outdoor time and MVPA were averaged across the three time points to represent the exposure and mediator variables, respectively. Mental health, dichotomized as flourishing/not flourishing, was the outcome in the mediation analysis. An interaction term tested if the mediation effect depended on outdoor time. Analyses were undertaken in 2019 using the mediation package in R. In univariate analyses, both MVPA (p < 0.001) and outdoor time (p = 0.05) were positive predictors of flourishing mental health. In mediation analyses, a small indirect mediation (OR: 1.02, 95% CI: 1.01-1.04) and no direct (1.00, 0.98-1.05) effect were noted, suggesting that MVPA mediates the effect of outdoor time on positive mental health. This effect did not vary as a function of outdoor time (interaction: 1.00, 0.99-1.01). Physical activity mediates the relationship between outdoor time and positive mental health. Outdoor time could promote positive mental health among youth through increases in physical activity.

Validation of a child version of the Three-Factor Eating Questionnaire in a Canadian sample: a psychometric tool for the evaluation of eating behaviour.

OBJECTIVE: To examine score validity and reliability of a child version of the twenty-one-item Three-Factor Eating Questionnaire (CTFEQ-R21) in a sample of Canadian children and adolescents and its relationship with BMI Z-score and food/taste preferences. DESIGN: Cross-sectional study. SETTING: School-based. PARTICIPANTS: Children (n 158), sixty-three boys (mean age 11·5 (sd 1·6) years) and ninety-five girls (11·9 (sd 1·9) years). RESULTS: Exploratory factor analysis revealed that the CTFEQ-R21 was best represented by four factors with item 17 removed (CFFEQ-R20), representing Cognitive Restraint (CR), Cognitive Uncontrolled Eating (UE 1), External Uncontrolled Eating (UE 2) and Emotional Eating (EE), accounting for 41·2 % of the total common variance with good scale reliability. ANOVA revealed that younger children reported higher UE 1 and CR scores than older children, and boys who reported high UE 1 scores had significantly higher BMI Z-scores. Children with high UE 1 scores reported a greater preference for high-protein and -fat foods, and high-fat savoury (HFSA) and high-fat sweet (HFSW) foods. Higher preference for high-protein, -fat and -carbohydrate foods, and HFSA, HFSW and low-fat savoury foods was found in children with high UE 2 scores. CONCLUSIONS: The study suggests that the CFFEQ-R20 can be used to measure eating behaviour traits and associations with BMI Z-score and food/taste preferences in Canadian children and adolescents. Future research is needed to examine the validity of the questionnaire in larger samples and other geographical locations, as well as the inclusion of extraneous variables such as parental eating or socio-economic status.

Revising the motivation and confidence domain of the Canadian assessment of physical literacy.

BACKGROUND: The Motivation and Confidence domain questionnaire in the Canadian Assessment of Physical Literacy (CAPL) was lengthy (36 single items that aggregate to five subscales), and thus burdensome to both participants and practitioners. The purpose of this study was to use factor analysis to refine the Motivation and Confidence domain to be used in the CAPL-Second Edition (CAPL-2). METHODS: Children, primarily recruited through free-of-charge summer day camps (n = 205, Mage = 9.50 years, SD = 1.14, 50.7% girls), completed the CAPL-2 protocol, and two survey versions of the Motivation and Confidence questionnaire. Survey 1 contained the Motivation and Confidence questionnaire items from the original CAPL, whereas Survey 2 contained a battery of items informed by self-determination theory to assess motivation and confidence. First, factor analyses were performed on individual questionnaires to examine validity evidence (i.e., internal structure) and score reliability (i.e., coefficient H and omega total). Second, factor analyses were performed on different combinations of questionnaires to establish the least burdensome yet well-fitted and theoretically aligned model. RESULTS: The assessment of adequacy and predilection, based on 16 single items as originally conceptualized within the CAPL, was not a good fit to the data. Therefore, a revised and shorter version of these scales was proposed, based on exploratory factor analysis. The self-determination theory items provided a good fit to the data; however, identified, introjected, and external regulation had low score reliability. Overall, a model comprising three single items for each of the following subscales was proposed for use within the CAPL-2: adequacy, predilection, intrinsic motivation, and perceived competence satisfaction. This revised domain fit well within the overall CAPL-2 model specifying a higher-order physical literacy factor (MLRχ2(63) = 81.45, p = 0.06, CFI = 0.908, RMSEA = 0.038, 90% CI (0.00, 0.060)). CONCLUSIONS: The revised and much shorter questionnaire of 12 items that aggregate to four subscales within the domain of Motivation and Confidence is recommended for use in the CAPL-2. The revised domain is aligned with the definition of motivation and confidence within physical literacy and has clearer instructions for completion.

Associations between 24 hour movement behaviours and global cognition in US children: a cross-sectional observational study.

BACKGROUND: Childhood and adolescence are crucial periods for brain development, and the behaviours during a typical 24 h period contribute to cognitive performance. The Canadian 24-Hour Movement Guidelines for Children and Youth recommend at least 60 min physical activity per day, 2 h or less recreational screen time per day, and 9-11 h sleep per night in children aged 8-11 years. We investigated the relationship between adherence to these recommendations and global cognition. METHODS: In this cross-sectional observational study, we obtained data from the first annual curated release of the Adolescent Brain Cognitive Development study, a 10-year longitudinal, observational study. Data were collected from 21 study sites across the USA between Sept 1, 2016, and Sept 15, 2017. The participants were 4524 US children aged 8-11 years from 20 study sites. Exposures of interest were adherence to the physical activity, recreational screen time, and sleep duration guideline recommendations. The primary outcome was global cognition, assessed with the NIH Toolbox (National Institutes of Health, Bethesda, MD, USA), which we analysed with multivariable linear mixed-effects models to examine the relations with movement behaviour variables. FINDINGS: Complete movement behaviour data were available for 4520 participants. The mean number of guideline recommendations met was 1·1 (SD 0·9). Overall, 2303 (51%) participants met the sleep recommendation, 1655 (37%) met screen time, and 793 (18%) met the physical activity recommendation. 3190 (71%) participants met at least one recommendation, whereas 216 (5%) of participants met all three recommendations. Global cognition was positively associated with each additional recommendation met (ß=1·44, 95% CI 0·82-2·07, p<0·0001). Compared with meeting none of the recommendations, associations with superior global cognition were found in participants who met all three recommendations (ß=3·89, 95% CI 1·43 to 6·34, p=0·0019), the screen time recommendation only (ß=4·25, 2·50-6·01, p<0·0001), and both the screen time and the sleep recommendations (ß=5·15, 3·56-6·74, p<0·0001). INTERPRETATION: Meeting the 24 h movement recommendations was associated with superior global cognition. These findings highlight the importance of limiting recreational screen time and encouraging healthy sleep to improve cognition in children. FUNDING: National Institutes of Health.

Changes in the Brain-Derived Neurotrophic Factor Are Associated with Improvements in Diabetes Risk Factors after Exercise Training in Adolescents with Obesity: The HEARTY Randomized Controlled Trial.

Obesity in youth increases the risk of type 2 diabetes (T2D), and both are risk factors for neurocognitive deficits. Exercise attenuates the risk of obesity and T2D while improving cognitive function. In adults, these benefits are associated with the actions of the brain-derived neurotrophic factor (BDNF), a protein critical in modulating neuroplasticity, glucose regulation, fat oxidation, and appetite regulation in adults. However, little research exists in youth. This study examined the associations between changes in diabetes risk factors and changes in BDNF levels after 6 months of exercise training in adolescents with obesity. The sample consisted of 202 postpubertal adolescents with obesity (70% females) aged 14-18 years who were randomized to 6 months of aerobic and/or resistance training or nonexercise control. All participants received a healthy eating plan designed to induce a 250/kcal deficit per day. Resting serum BDNF levels and diabetes risk factors, such as fasting glucose, insulin, homeostasis model assessment (HOMA-B-beta cell insulin secretory capacity) and (HOMA-IS-insulin sensitivity), and hemoglobin A1c (HbA1c), were measured after an overnight fast at baseline and 6 months. There were no significant intergroup differences on changes in BDNF or diabetes risk factors. In the exercise group, increases in BDNF were associated with reductions in fasting glucose (ß = -6.57, SE = 3.37, p = 0.05) and increases in HOMA-B (ß = 0.093, SE = 0.03, p = 0.004) after controlling for confounders. No associations were found between changes in diabetes risk factors and BDNF in controls. In conclusion, exercise-induced reductions in some diabetes risk factors were associated with increases in BDNF in adolescents with obesity, suggesting that exercise training may be an effective strategy to promote metabolic health and increases in BDNF, a protein favoring neuroplasticity. This trial is registered with ClinicalTrials.gov NCT00195858, September 12, 2005 (funded by the Canadian Institutes of Health Research).

Refining the Canadian Assessment of Physical Literacy based on theory and factor analyses.

BACKGROUND: The Canadian Assessment of Physical Literacy (CAPL) is a 25-indicator assessment tool comprising four domains of physical literacy: (1) Physical Competence, (2) Daily Behaviour, (3) Motivation and Confidence, and (4) Knowledge and Understanding. The purpose of this study was to re-examine the factor structure of CAPL scores and the relative weight of each domain for an overall physical literacy factor. Our goal was to maximize content representation, and reduce construct irrelevant variance and participant burden, to inform the development of CAPL-2 (a revised, shorter, and theoretically stronger version of CAPL). METHODS: Canadian children (n = 10,034; Mage = 10.6, SD = 1.2; 50.1% girls) completed CAPL testing at one time point. Confirmatory factor analysis was used. RESULTS: Based on weak factor loadings (λs < 0.32) and conceptual alignment, we removed body mass index, waist circumference, sit-and-reach flexibility, and grip strength as indicators of Physical Competence. Based on the factor loading (λ < 0.35) and conceptual alignment, we removed screen time as an indicator of Daily Behaviour. To reduce redundancy, we removed children's activity compared to other children as an indicator of Motivation and Confidence. Based on low factor loadings (λs < 0.35) and conceptual alignment, we removed knowledge of screen time guidelines, what it means to be healthy, how to improve fitness, activity preferences, and physical activity safety gear indicators from the Knowledge and Understanding domain. The final refined CAPL model was comprised of 14 indicators, and the four-factor correlated model fit the data well (r ranged from 0.08 to 0.76), albeit with an unexpected cross-loading from Daily Behaviour to knowledge of physical activity guidelines (mean- and variance-adjusted weighted least square [WLSMV] χ2(70) = 1221.29, p < 0.001, Comparative Fit Index [CFI] = 0.947, root mean square error of approximation [RMSEA] = 0.041[0.039, 0.043]). Finally, our higher-order model with Physical Literacy as a factor with indicators of Physical Competence (λ = 0.68), Daily Behaviour (λ = 0.91), Motivation and Confidence (λ = 0.80), and Knowledge and Understanding (λ = 0.21) fit the data well. CONCLUSIONS: The scores from the revised and much shorter 14-indicator model of CAPL can be used to assess the four correlated domains of physical literacy and/or a higher-order aggregate physical literacy factor. The results of this investigation will inform the development of CAPL-2.

Canadian Assessment of Physical Literacy Second Edition: a streamlined assessment of the capacity for physical activity among children 8 to 12 years of age.

BACKGROUND: The Canadian Assessment of Physical Literacy (CAPL) assesses the capacity of children to lead a physically active lifestyle. It is comprised of a battery of standardized assessment protocols that reflect the Canadian consensus definition of physical literacy. The Royal Bank of Canada Learn to Play - Canadian Assessment of Physical Literacy study implemented the CAPL with 10,034 Canadian children (50.1% female), 8 to 12 years of age. Feedback during data collection, necessary changes identified by the coordinating centre, and recent data analyses suggested that a streamlined, second edition of the CAPL was required. The purpose of this paper is to describe the methods used to develop the CAPL second edition (CAPL-2). METHODS: The larger dataset created through the RBC-Learn to Play CAPL study enabled the re-examination of the CAPL model through factor analyses specific to Canadian children 8 to 12 years of age from across Canada. This comprehensive database was also used to examine the CAPL protocols for redundancy or variables that did not contribute significantly to the overall assessment. Removing redundancy had been identified as a priority in order to reduce the high examiner and participant burden. The "lessons learned" from such a large national surveillance project were reviewed for additional information regarding the changes that would be required to optimize the assessment of children's physical literacy. In addition, administrative changes, improvements, and corrections were identified as necessary to improve the quality and accuracy of the CAPL manual and training materials. RESULTS: For each domain of the CAPL, recommended changes based on the factor analyses, qualitative feedback and theoretical considerations significantly reduced the number of protocols. Specific protocol combinations were then evaluated for model fit within the overarching concept of physical literacy. The CAPL-2 continues to reflect the four components of the Canadian consensus definition of physical literacy: Motivation and Confidence, Physical Competence, Knowledge and Understanding, and engagement in Physical Activity Behaviour. The CAPL-2 is comprised of three Physical Competence protocols (plank, Progressive Aerobic Cardiovascular Endurance Run [PACER], Canadian Agility and Movement Skill Assessment [CAMSA]), two Daily Behaviour protocol (pedometer steps, self-reported physical activity), and a 22-item questionnaire assessing the physical literacy domains of Motivation and Confidence, and Knowledge and Understanding. Detailed information about the CAPL-2 is available online ( www.capl-eclp.ca ). CONCLUSIONS: The CAPL-2 dramatically reduces examiner and participant burden (three Physical Competence protocols, two Daily Behaviour protocols, and a 22-response questionnaire; versus eight Physical Competence protocols, three Daily Behaviour protocols and a 72-response questionnaire for the original CAPL), while continuing to be a comprehensive assessment of all aspects of children's physical literacy using the Canadian consensus definition of this term. Like the original, the CAPL-2 continues to offer maximum flexibility to practitioners, who can choose to complete the entire CAPL-2 assessment, only one or more domains, or select individual protocols. Regardless of the assessment selected, scores are available to interpret the performance of each child relative to Canadian children of the same age and sex. All of the protocols included in the CAPL-2 have published reports of validity and reliability for this age group (8 to 12 years). The detailed manual for CAPL-2 administration, along with training materials and other resources, are available free of charge on the CAPL-2 website ( www.capl-eclp.ca ). All CAPL-2 materials and resources, including the website, are available in both English and French.

Influence of sleep on developing brain functions and structures in children and adolescents: A systematic review.

This systematic review examined the associations between sleep and brain functions and structures in children and adolescents aged 1-17 ys. Included studies (n = 24) were peer-reviewed and met the a priori determined population (apparently healthy children and adolescents aged 1 y to 17 ys), intervention/exposure/comparator (various sleep characteristics including duration, architecture, quality, timing), and outcome criteria (brain functions and/or brain structures, excluding cognitive function outcomes). Collectively, the reviewed studies report some relationships between inadequate sleep and resultant differences in brain functions or structures. Although the research presented supports and offers more insight into the importance of sleep for the developing brain of children and adolescents, no firm conclusions that apply broadly may be drawn from these results, particularly because of the diversity of the sleep variables and outcomes. However, it is clear that sleeping habits in the pediatric population should be prioritized. Health care providers should continue to recommend healthy sleep practices and adequate time for sleep, as they are essential for overall health, including brain health.

Effects of aerobic training, resistance training, or both on brain-derived neurotrophic factor in adolescents with obesity: The hearty randomized controlled trial.

Brain derived neurotrophic factor (BDNF) is a protein that plays a critical role in modulating cognition in animals and humans. Aerobic exercise often increases BDNF in adults, but effects of this exercise modality and others among adolescents remain uncertain. This study examined the effects of aerobic training, resistance training, and combined training on resting serum BDNF levels in adolescents with overweight and obesity. After a 4-week pre-randomization treatment, 304 post-pubertal, adolescents with overweight or obesity (70% females) aged 14-18 years were randomized to one of four groups for 22 weeks: aerobic training (N = 75), resistance training (N = 78), combined aerobic and resistance training (N = 75), or non-exercising control (N = 76). All participants received dietary counseling targeting a daily energy deficit of 250 kcal. The exercise prescription was 4 times per week, progressing to 45 min/session for the aerobic and resistance groups and 90 min/session for the combined group. Resting serum BDNF levels were measured at baseline and 6-months. Results showed that in both intention-to-treat (ITT) and per protocol (≥70% adherence to prescribed sessions) analyses, there were no significant within- or between-group changes in BDNF. Findings indicate that aerobic training, resistance training or their combination did change serum BDNF levels in adolescents with overweight and obesity. TRIAL REGISTRATION: ClinicalTrials.Gov NCT00195858 http://clinicaltrials.gov/show/NCT00195858, September 12, 2005 (Funded by the Canadian Institutes of Health Research).

Out with the old, in with the new: Assessing change in screen time when measurement changes over time.

We examined if screen time can be assessed over time when the measurement protocol has changed to reflect advances in technology. Beginning in 2011, 929 youth (9-12 years at time one) living in in New Brunswick (Canada) self-reported the amount of time spent watching television (cycles 1-13), using computers (cycles 1-13), and playing video games (cycles 3-13). Using longitudinal invariance to test a shifting indicators model of screen time, we found that the relationships between the latent variable reflecting overall screen time and the indicators used to assess screen time were invariant across cycles (weak invariance). We also found that 31 out of 37 indicator intercepts were invariant, meaning that most indicators were answered similarly (i.e., on the same metric) across cycles (partial strong invariance), and that 28 out of 37 indicator residuals were invariant indicating that similar sources of error were present over time (partial strict invariance). Overall, across all survey cycles, 76% of indicators were fully invariant. Whereas issues were noted when new examples of screen-based technology (e.g., iPads) were added, having established partial invariance, we suggest it is still possible to assess change in screen time despite having changing indicators over time. Although it is not possible to draw definitive conclusions concerning other self-report measures of screen time, our findings may assist other researchers considering modifying self-report measures in longitudinal studies to reflect technological advancements and increase the precision of their results.

Factor Structure of Responses to the Portuguese Version of Questions About Screen Time-Based Sedentary Behavior Among Adolescents.

BACKGROUND: This study aimed to examine the factor structure of responses to the Portuguese version of questions related to screen time-based sedentary behavior among adolescents. METHODS: This cross-sectional study with a sample of 1083 adolescents aged 14-19 years was conducted in Brazil. The sample was randomly divided into 2 groups for an exploratory factor analysis and for a confirmatory factor analysis. Screen time was investigated by a Portuguese version of questions about time sitting in front of television, computer, and video games on weekdays and weekends. RESULTS: Scree plots showed 2 factors with eigenvalues above 1. One factor was formed by items about television and computer use, and the other factor was formed by items about video game use. The exploratory factor analysis with 2 factors resulted in factor loadings above .60. A second model with 1 factor was estimated and resulted in factor loadings above .55. A confirmatory factor analysis was estimated based on the 2-factor exploratory factor analysis and goodness-of-fit statistics were adequate. Confirmatory factor analysis with 1 factor had goodness-of-fit statistics adequate. CONCLUSIONS: The Portuguese language version of self-report screen time had 2 possible factor solutions, and items demonstrated good factor structure with reasonable reliability making it suitable for use in the future studies.

Physical activity and depressive symptoms after breast cancer: Cross-sectional and longitudinal relationships.

OBJECTIVE: The objective of this study was to examine the cross-sectional and longitudinal relationships between moderate-to-vigorous intensity physical activity (MVPA) and depressive symptoms in women after treatment for breast cancer. METHOD: Accelerometer data on MVPA and self-report data on frequency of depressive symptoms were collected five times at ∼ 3-month intervals from women (Mage at Time 1 = 55.01 ± 10.96 years) who had completed treatment for breast cancer 3 months prior to study inception. Data were analyzed using latent growth modeling with structured residuals. RESULTS: Levels of MVPA decreased, on average, by .52 min every 3 months (p < .001), whereas the frequency of depressive symptoms was stable. MVPA was inversely and significantly related cross-sectionally with depressive symptoms, but not longitudinally. Also, there was no evidence of a bidirectional predictive relationship between MVPA and depressive symptoms. CONCLUSION: Although higher levels of MVPA were associated with less frequent depressive symptoms cross-sectionally in women after treatment for breast cancer, MVPA did not predict frequency of depressive symptoms or vice versa. Common etiologic or shared risk factors underpinning the cross-sectional relationships between depressive symptoms and MVPA should be studied across the transition from treatment to survivorship. (PsycINFO Database Record