Study protocol for the ACTIVE SCHOOL study investigating two different strategies of physical activity to improve academic performance in Schoolchildren.

BACKGROUND: Previous research has suggested that school-based physical activity (PA) interventions may have a positive impact on academic performance. However, existing literature on school-based interventions encompasses various forms of PA, spanning from vigorous intensity PA outside the academic classes to light intensity PA and movement integrated into academic learning tasks, and results on academic performance are inconclusive. ACTIVE SCHOOL will implement two different PA interventions for one school year and assess the effects on the pupils' academic performance, with math performance as the primary outcome. METHODS/DESIGN: The ACTIVE SCHOOL project consists of two phases: 1) Development phase and 2) Randomized Controlled Trial (RCT). In phase one, two interventions were developed in collaboration with school staff. The two interventions were tested in an 8-weeks feasibility study. In phase two, a RCT-study with three arms will be conducted in 9-10-year-old children for one school year. The RCT-study will be carried out in two intervention rounds during the school years 2023/2024 and 2024/2025. Schools will be randomized to one of two interventions or control;1) Run, Jump & Fun intervention (4 × 30 min/week of moderate-to-vigorous physical activity; 2) Move & Learn intervention (4 × 30 min/week focusing on embodied learning in math and Danish lessons); or 3) a control condition, consisting of normal teaching practices. Outcome measures include academic performance, PA level, cognitive functions, cardiorespiratory fitness, anthropometry, well-being and school motivation (collected before, during and after the intervention period). A process evaluation will be conducted to assess implementation. DISCUSSION: The ACTIVE SCHOOL study will expand knowledge regarding the impact of PA on academic performance. The study will have the potential to significantly contribute to future research, as well as the scientific and educational debate on the best way to implement PA to support education and learning. TRIAL REGISTRATION: The study was registered on the 25th of October 2022 in ClinicalTrials.gov, NCT05602948.

The metabolic syndrome is frequent in children and adolescents with type 1 diabetes compared to healthy controls.

OBJECTIVE: There is a rise in overweight and obesity among children and adolescents with type 1 diabetes (T1D) in parallel with the rise in the metabolic syndrome (MetS) among children and adolescents. The aim of the study was to describe the prevalence and characteristics of MetS in children and adolescents with T1D compared to their healthy counterparts. RESEARCH DESIGN AND METHODS: The study includes two Danish cohorts; (i) the Copenhagen cross sectional cohort 2016 of 277 children and adolescents with T1D that attend the pediatric outpatient clinic at a large hospital in greater Copenhagen and (ii) the CHAMPS-study DK which is a population-based cohort study of Danish children and adolescents (control cohort). Participants were categorized to have MetS if at least two of the following criteria were met: (i) systolic and/or diastolic blood pressure ≥ 90th percentile, (ii) waist circumference ≥90th percentile, and (iii) triglyceride ≥90th percentile and/or HDL ≤10th percentile. RESULTS: The prevalence of children with Mets in the T1D cohort was higher than in the control cohort (p = 0.002). Moreover, participants with T1D had MetS at a lower level of BMI (p < 0.001) and waist circumference (p < 0.001) than participants with MetS from the control cohort (z-scores = 0.90 and 1.51). Participants with MetS were younger than the other T1D participants (median 12.8 [9.9,14.8] vs. median 14.6 [11.2,16.9] years, p = 0.006). CONCLUSIONS: Children and adolescents with T1D have an increased risk of MetS compared to healthy controls and clinicians and caretakers should consider early prevention and health promotion strategies.

Intake of n-3 LCPUFA and trans-fatty acids is unrelated to development in body mass index and body fat among children.

BACKGROUND: The number of children and adolescents with obesity has increased worldwide. Some studies have found an increase in the intake of n-3 long-chain polyunsaturated fatty acid (LCPUFA) to be beneficial for weight and obesity status. The objectives of this study were to examine if intake of trans-fatty acids (TFA) and n-3 LCPUFA at school start was associated with weight and body fat development in the following 3 and 7 years, and if substituting other fats for n-3 LCPUFA in regression models influenced weight and body fat development. METHODS: A total of 285 children (boys:130, girls:155) were included in this study. Weight, height and skinfold thickness (SF) of children were measured at age 6, 9 and 13 years by trained research personnel. Multivariate linear regression models were used to investigate the associations between n-3 LCPUFA or TFA intake and subsequent changes in body mass index (BMI) or SF. To investigate substitution effects, we constructed regression models including information on n-3 LCPUFA and all other energy given components of the diet, except for the nutrient to be substituted (all other fats and specific subgroups; saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) and other polyunsaturated fatty acids (PUFAs)). RESULTS: No significant associations were observed between intake of TFA or n-3 LCPUFA and changes in BMI and SF. Also, results from regression analysis showed substituting other fats for n-3 LCPUFA did not associate with BMI or SF development. CONCLUSION: The lack of associations between n-3 LCPUFA and TFA and adiposity suggests that fat composition in the diet does not play a major role in obesity development among school-aged children.

Three-Year Intervention Effects on Food and Beverage Intake-Results from the Quasi-Experimental Copenhagen School Child Intervention Study (CoSCIS).

The diet of Danish children is often not in accordance with dietary guidelines. We aimed to evaluate changes in the intake of selected foods and beverages during a multi-component school-based physical activity intervention, and to investigate if changes were modified by socioeconomic status (SES). The study included 307 children (intervention group: 184; comparison group: 123) with information on dietary intake pre- and post-intervention as well as on SES. Linear regression models were conducted to assess the effect of the intervention on changes in dietary factors. Children from the intervention group increased their intake of whole-grain bread during the intervention (group means: 6.1 g/d (95% CI: 2.2 to 10.0) vs. 0.3 g/d (95% CI: -3.1 to 3.7) in the comparison group, p = 0.04). A significant interaction between SES and group allocation was observed to change in fruit intake (p = 0.01). Among children from low SES families, only those from the comparison group decreased their fruit intake (group means: -40.0 g/d (95% CI: -56.0 to -23.9) vs. 9.3 g/d (95% CI: -16.1 to 94) in the intervention group, p = 0.006). The present study found no convincing effect of introducing a multi-component intervention on dietary intake except a small beneficial effect on whole-grain bread consumption. However, beneficial intervention effects in fruit intake were found particularly among children from low SES families.

School-based interventions modestly increase physical activity and cardiorespiratory fitness but are least effective for youth who need them most: an individual participant pooled analysis of 20 controlled trials.

OBJECTIVES: To determine if subpopulations of students benefit equally from school-based physical activity interventions in terms of cardiorespiratory fitness and physical activity. To examine if physical activity intensity mediates improvements in cardiorespiratory fitness. DESIGN: Pooled analysis of individual participant data from controlled trials that assessed the impact of school-based physical activity interventions on cardiorespiratory fitness and device-measured physical activity. PARTICIPANTS: Data for 6621 children and adolescents aged 4-18 years from 20 trials were included. MAIN OUTCOME MEASURES: Peak oxygen consumption (VO2Peak mL/kg/min) and minutes of moderate and vigorous physical activity. RESULTS: Interventions modestly improved students' cardiorespiratory fitness by 0.47 mL/kg/min (95% CI 0.33 to 0.61), but the effects were not distributed equally across subpopulations. Girls and older students benefited less than boys and younger students, respectively. Students with lower levels of initial fitness, and those with higher levels of baseline physical activity benefitted more than those who were initially fitter and less active, respectively. Interventions had a modest positive effect on physical activity with approximately one additional minute per day of both moderate and vigorous physical activity. Changes in vigorous, but not moderate intensity, physical activity explained a small amount (~5%) of the intervention effect on cardiorespiratory fitness. CONCLUSIONS: Future interventions should include targeted strategies to address the needs of girls and older students. Interventions may also be improved by promoting more vigorous intensity physical activity. Interventions could mitigate declining youth cardiorespiratory fitness, increase physical activity and promote cardiovascular health if they can be delivered equitably and their effects sustained at the population level.

Does Additional Physical Education Improve Exam Performance at the End of Compulsory Education? A Secondary Analysis from a Natural Experiment: The CHAMPS-Study DK.

It remains unclear whether the provision of additional physical activity in school improves academic outcomes. We conducted a secondary analysis of the Childhood Health, Activity, and Motor Performance School Study Denmark (CHAMPS-study DK), a natural experiment based on a trebling of curricular physical education, to investigate whether children receiving additional physical education performed better on their academic exams at the conclusion of compulsory education (i.e., 9th grade). Children from six intervention schools received 3-7 years of exposure to 270 weekly minutes of physical education (sports schools), while children from four control schools received the 90-min national standard (normal schools). Academic performance was based on the standard Danish 7-point scale (ranging from -03 to 12) and retrieved from national registries. The primary outcome was calculated as the average exam grade. Comparisons of participants at sports and normal schools were adjusted for individual socioeconomic factors and school-level academic environment. There were no differences in the pooled exam performance among 691 sports- and 510 normal-school participants (0.20 (95% confidence interval: -0.12 to 0.52)). Results for subject-specific exams indicated similar results. This analysis from a non-randomized natural experiment did not provide evidence that simply adding additional physical education is sufficient to affect academic performance relative to the national standard.

Weekly variation in markers of cardiometabolic health - the possible effect of weekend behavior - a cross-sectional study.

BACKGROUND: Adolescents' health-related behavior varies from weekday to weekend. Only few studies, however, have examined to which degree such variation will affect markers of cardiometabolic health. Therefore, the primary aim of this study is to examine if markers of cardiometabolic health differ between different days of the week in adolescents. METHODS: This cross-sectional school-based study included up to 581 participants, 11-17 years old. Markers of metabolic health were insulin, glucose, triglyceride, HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C) and blood pressure. Linear mixed regression modelling was used to examine the cardiometabolic profile across weekdays. RESULTS: Significant declining trends were observed across the week in adolescents' levels of cardiometabolic health markers. Lower levels of insulin (16.1%), glucose (2.6%) and triglyceride (24.7%) were observed on Fridays compared to Mondays (p ≤ 0.006). Gradual improvement in measurement profiles across weekdays was less apparent for HDL-C, LDL-C, systolic blood pressure and diastolic blood pressure (P ≥ 0.06). Analyses stratified by sex suggested a more noticeable pattern of gradual improvement across weekdays in boys than in girls. CONCLUSION: Significantly lower levels of insulin, glucose and triglyceride were observed in adolescents on Fridays compared to Mondays. However, when sex specific analyses were performed significant profile variations were only observed across the week in boys. More research is needed to better understand which behavioral factors in particular seem to influence weekly variation in markers of cardiometabolic health - especially since such variation potentially will have an impact on how assessments of markers of cardiometabolic health optimally should be planned, standardized and carried out, both in research and in medical practice.

Motor-Enriched Encoding Can Improve Children's Early Letter Recognition.

It is not known how effective specific types of motor-enriched activities are at improving academic learning and early reading skills in children. The aim of this study was to investigate whether fine or gross motor enrichment during a single session of recognizing letters "b"/"d" can improve within-session performance or delayed retention the following day in comparison to letter recognition practice without movement. Furthermore, the aim was to investigate children's motivation to perform the specific tasks. We used a randomized controlled intervention study-design to investigate the effect of 10-min motor-enriched "b"/"d" letter training on children's ability to recognize the letters "b" and "d" (n = 127, mean age = 7.61 ± SD = 0.44 years) acutely, and in a delayed retention test. Three groups were included: a fine motor-enriched group (FME), a gross motor-enriched group (GME), that received 10 min of "b" and "d" training with enriched gestures (fine or gross motor movements, respectively), and a control group (CON), which received non motor-enriched "b"/"d" training. The children's ability to recognize "b" and "d" were tested before (T0), immediately after (T1), and one day after the intervention (T2) using a "b"/"d" Recognition Test. Based on a generalized linear mixed model a significant group-time interaction was found for accuracy in the "b"/"d" Recognition Test. Specifically, FME improved their ability to recognize "b"/"d" at post intervention (T0→T1, p = 0.008) and one-day retention test (T0→T2, p < 0.001) more than CON. There was no significant difference in change between GME and CON. For reaction time there were no significant global interaction effects observed. However, planned post hoc comparisons revealed a significant difference between GME and CON immediately after the intervention (T0→T1, p = 0.03). The children's motivation-score was higher for FME and GME compared to CON (FME-CON: p = 0.01; GME-CON: p = 0.01). The study demonstrated that fine motor-enriched training improved children's letter recognition more than non motor activities. Both types of motor training were accompanied by higher intrinsic motivation for the children compared to the non motor training group. The study suggests a new method for motor-enriched letter learning and future research should investigate the underlying mechanisms.

Dynamic Balance, but Not Precision Throw, Is Positively Associated with Academic Performance in Children.

We analyzed the longitudinal association between dynamic balance and throwing skill with academic performance and whether waist circumference mediated these relationships. The current one-year longitudinal study followed 1020 first (mean age 7.87 ± 0.34 years) through fifth grade (mean age 11.87 ± 0.37 years) children, measured twice in 2010 and 2011. Dynamic balance and precision throw were measures of motor competence. Waist circumference was measured with a measuring tape at the umbilicus level. Academic performance was assessed by a combined score of standardized Danish language and math tests. Structural equation modeling was used for analysis. All coefficients are standardized. Balance was associated with academic performance when both sexes were combined (ß = 0.126, 95% CI: 0.074 to 0.179), and waist circumference partially mediated the relationship (ß = 0.021, 95% CI: 0.008 to 0.034). For boys, balance was associated with academic performance, but waist circumference did not mediate the association. For girls, balance presented direct, mediated (via waist circumference), and total associations with academic performance. Dynamic balance is an important gross motor function that was longitudinally related to academic performance, and waist circumference partially mediated the relationship. Precision throw was not found to be associated with academic performance in both sexes combined or when analyzed separately.

Substituting prolonged sedentary time and cardiovascular risk in children and youth: a meta-analysis within the International Children's Accelerometry database (ICAD).

BACKGROUND: Evidence on the association between sitting for extended periods (i.e. prolonged sedentary time (PST)) and cardio-metabolic health is inconsistent in children. We aimed to estimate the differences in cardio-metabolic health associated with substituting PST with non-prolonged sedentary time (non-PST), light (LIPA) or moderate-to-vigorous physical activity (MVPA) in children. METHODS: Cross-sectional data from 14 studies (7 countries) in the International Children's Accelerometry Database (ICAD, 1998-2009) was included. Accelerometry in 19,502 participants aged 3-18 years, together with covariate and outcome data, was pooled and harmonized. Iso-temporal substitution in linear regression models provided beta coefficients (95%CI) for substitution of 1 h/day PST (sedentary time accumulated in bouts > 15 min) with non-PST, LIPA or MVPA, for each study, which were meta-analysed. RESULTS: Modelling substitution of 1 h/day of PST with non-PST suggested reductions in standardized BMI, but estimates were > 7-fold greater for substitution with MVPA (- 0.44 (- 0.62; - 0.26) SD units). Only reallocation by MVPA was beneficial for waist circumference (- 3.07 (- 4.47; - 1.68) cm), systolic blood pressure (- 1.53 (- 2.42; - 0.65) mmHg) and clustered cardio-metabolic risk (- 0.18 (- 0.3; - 0.1) SD units). For HDL-cholesterol and diastolic blood pressure, substitution with LIPA was beneficial; however, substitution with MVPA showed 5-fold stronger effect estimates (HDL-cholesterol: 0.05 (0.01; 0.10) mmol/l); diastolic blood pressure: - 0.81 (- 1.38; - 0.24) mmHg). CONCLUSIONS: Replacement of PST with MVPA may be the preferred scenario for behaviour change, given beneficial associations with a wide range of cardio-metabolic risk factors (including adiposity, HDL-cholesterol, blood pressure and clustered cardio-metabolic risk). Effect estimates are clinically relevant (e.g. an estimated reduction in waist circumference of ≈1.5 cm for 30 min/day replacement). Replacement with LIPA could be beneficial for some of these risk factors, however with substantially lower effect estimates.

Correction to: Physical activity intensity, bout-duration, and cardiometabolic risk markers in children and adolescents.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The longitudinal relationship between motor competence and measures of fatness and fitness from childhood into adolescence / Relação longitudinal entre a coordenação motora e as medidas de gordura e aptidão física da infância à adolescência

Abstract Objectives: To examine longitudinal (seven years) relationships among cardiorespiratory fitness (VO2peak), body fatness, and motor competence. Method: Data were collected as part of the Copenhagen School Child Intervention Study (CoSCIS). Body fatness was assessed by the sum of four skinfolds. VO2peak was measured directly in a continuous running protocol. Motor competence was assessed using the Körperkoordinationtest für Kinder. This study used multilevel linear mixed models to evaluate the reciprocal longitudinal association between body fatness, VO2peak, and motor competence. All regressions were stratified by sex and adjusted by intervention and pubertal status. All variable coefficients were standardized. Results: A reciprocal relationship was observed between children's motor competence with body fatness and VO2peak at the seven-year follow-up (6 -13 years of age). Children with higher motor competence at baseline had a lower risk of having higher body fatness (βboys = −0.45, 95% CI: −0.52 to −0.38; βgirls = −0.35, 95% CI: −0.42 to −0.28) and higher VO2peak (βboys = 0.34, 95% CI: 0.27 -0.40; βgirls = 0.27, 95% CI: 0.20 -0.33) during childhood. Alternatively, higher body fatness or lower levels of VO2peak at baseline were associated with lower motor competence during childhood. Conclusions: These data suggest motor competence, body fatness, and VO2peak demonstrate reciprocal relationships across childhood (6 -13 years of age). Interventions addressing motor competence, cardiorespiratory fitness, and body fatness in early childhood are recommended, as intervention effects are likely to be enhanced because of the mutual reciprocal associations between these three variables.

Resumo Objetivos: Examinar as relações longitudinais (sete anos) entre a aptidão cardiorrespiratória (VO2 pico), gordura corporal e coordenação motora. Método: Os dados foram coletados como parte do Copenhagen School Child Intervention Study (CoSCIS). A gordura corporal foi avaliada pela soma de quatro dobras cutâneas. O VO2 pico foi medido diretamente em um protocolo de corrida contínua. A coordenação motora foi avaliada com o teste de coordenação corporal para crianças (Körperkoordination für Kinder - KTK). Usamos modelos lineares mistos multiníveis para avaliar a associação longitudinal recíproca entre a gordura corporal, o VO2 pico e a coordenação motora. Todas as regressões foram estratificadas por sexo e ajustadas para intervenção e estado puberal. Todos os coeficientes das variáveis foram padronizados. Resultados: Observamos uma relação recíproca entre a coordenação motora e a gordura corporal. As crianças com maior coordenação motora no início do estudo apresentaram menor risco de ter maior nível de gordura corporal (βmeninos = -0,45, IC de 95%: -0,52: -0,38; βmeninas = -0,35, IC de 95%: -0,42: -0,28) e maior VO2 pico (βmeninos = 0,34, IC de 95%: 0,27: 0,40; βmeninas = 0,27, IC de 95%: 0,20: 0,33). Por outro lado, maior nível de gordura corporal ou menores níveis de VO2 pico no início do estudo foram associados a menor coordenação motora durante a infância. Conclusões: Esses dados sugerem que a coordenação motora, gordura corporal e VO2 pico demonstram relações recíprocas durante a infância (6-13 anos). São recomendadas intervenções que abordem a coordenação motora, a aptidão cardiorrespiratória e a gordura corporal na primeira infância, pois os efeitos da intervenção são provavelmente maiores devido às associações recíprocas mútuas entre essas três variáveis.

Associations between serum and plasma brain-derived neurotrophic factor and influence of storage time and centrifugation strategy.

The aims of the study were to clarify the impact of storage time and centrifugation strategy on brain-derived neurotrophic factor (BDNF) levels in human serum and plasma samples. In addition, we analyzed associations between BDNF levels, cardiorespiratory fitness and waist circumference. Seventeen healthy males (25.2 (4.1) years) were included in the study. Blood samples were drawn after an overnight fast and treated to different protocols, varying in time before centrifugation and centrifugation strategy. BDNF was analyzed in serum, normal plasma (NP) and platelet-poor plasma (PPP). Also, waist circumference and cardiorespiratory fitness were measured. A large increase was observed in serum BDNF levels during the first hour of clotting. BDNF in NP correlated with PPP, whereas no correlations were found between BDNF in serum and plasma. Though not statistical significant, correlations between fitness and BDNF in serum changed from positive at 30 min. to negative when clotting time was ≥60 min. In conclusion, BDNF levels in serum were affected by clotting time, whereas BDNF levels in plasma were influenced by centrifugation strategy. Importantly, BDNF in serum and plasma appears to reflect two different pools of BDNF. The biological relevance of the velocity of BDNF release during clotting and its dependence upon fitness must be investigated further.

Implementation of a successful long-term school based physical education intervention: Exploring provider and programme characteristics.

There is an ongoing need for research focusing on how to implement physical activity programmes into a school setting. This includes documentation of the extent to which programmes are compatible with the basic views of providers and their local practices. The present study explores the Svendborgproject - a programme tripling the amount of physical education in six public schools, sustaining it for 10-years and documenting a decreased incidence of overweight, obesity and cardiovascular risk factors. The aim was to analyse provider and programme characteristics of the Svendborgproject to gain insights into providers motives for adopting, implementing, and maintaining the programme. Six school heads and six teachers were interviewed to explore how they perceived programme compatibility to their school's practice and their own role as providers. Both teachers and school heads found the additional lessons a valuable asset that fitted existing school values and priorities. Additionally, physical education teachers participated in a course providing new perspectives and teaching methods that aided the implementation of the programme. Lastly, school heads stressed that implementation fidelity was heavily dependent on the dedication of physical education teachers and on having simple programme requirements that made it clear what could be expected of the programme.

Bone mass development is sensitive to insulin resistance in adolescent boys.

PURPOSE: Insulin resistance may exert a negative influence on bone mass in childhood and adolescence. The objective was to assess the association between insulin resistance and total body less head (TBLH) bone mineral content (BMC) and to investigate whether body composition, physical activity or osteocalcin levels may influence this association. METHODS: A longitudinal study with follow-up over more than 6 years was performed and included 562 apparently healthy participants with a mean age of 9.6 years at baseline. Participants underwent DXA scanning at baseline. At the two follow-ups, participants had performed another DXA scanning, had blood samples taken for fasting insulin, glucose and osteocalcin and had physical activity measured with an accelerometer. HOMA-IR was calculated as an index of insulin resistance. RESULTS: HOMA-IR was negatively associated with TBLH BMC in boys at follow-ups (ß = -31.4, p < 0.001) after adjustment for maturity, height, bone area, and baseline level of TBLH BMC. The negative association remained almost unchanged after further adjustments for body composition and physical activity. No association between HOMA-IR and TBLH BMC was found in girls. CONCLUSION: Insulin resistance may be detrimental for bone development through puberty in boys independent of body composition and the level of physical activity.

Physical Activity and Sedentary Time Are Positively Associated With Academic Performance: A 3-Year Longitudinal Study.

BACKGROUND: To analyze the longitudinal association between academic performance and moderate to vigorous physical activity (MVPA), vigorous physical activity (VPA), and sedentary (SED) in a 3-year longitudinal study. A secondary aim was to determine whether MVPA and VPA were indirectly related with academic performance via waist circumference (WC). METHODS: Physical activity (PA) and SED were measured by accelerometers. Academic performance was assessed by national tests in Danish and Math. Structural equation modeling was performed to evaluate whether MVPA, VPA, and SED were associated with academic performance and the potential PA-academic performance indirect relationship via WC. RESULTS: MVPA and VPA were associated with academic performance, mediated via WC (ß = 0.036; 95% confidence interval [CI], 0.002 to 0.070 and ß = 0.096; 95% CI, 0.027 to 0.164, respectively). SED was directly associated with academic performance (ß = 0.124; 95% CI, 0.030 to 0.217, MVPA model and ß = 0.132; 95% CI, 0.044 to 0.221, VPA model). WC was negatively associated with academic performance. CONCLUSIONS: Both PA and SED time were positively associated with academic performance. Based on this, PA should be encouraged in children and youth not only to promote physical health but also to promote academic performance. Future studies should distinguish between school-related SED and other SED activities and their relationship with academic performance.

Muscle Fitness Changes During Childhood Associates With Improvements in Cardiometabolic Risk Factors: A Prospective Study.

BACKGROUND: The role of muscle fitness in controlling cardiometabolic risk factors during childhood is incompletely understood. METHODS: A prospective observational design including 6- to 11-year-old children (n = 512) was used to study associations between 1.5-year changes in handgrip strength, standing vertical jump displacement, the short shuttle run, and a composite of these with changes in composite and single cardiometabolic risk markers. The authors modeled sequential mixed linear regressions controlling for changes in cardiorespiratory fitness, waist circumference, and other putative confounding variables. RESULTS: Statistically significant associations, standardized beta (95% confidence intervals), were observed between changes in composite muscle fitness -0.19 (-0.30 to -0.07), muscular strength -0.15 (-0.25 to -0.06), and agility 0.14 (0.04 to 0.23), but not muscular power -0.06 (-0.14 to 0.03) with changes in the composite risk score. In sex-stratified analysis, associations were robust in girls, but not in boys. Control for changes in cardiorespiratory fitness and waist circumference greatly attenuated associations. Changes in muscle fitness were strongly associated with changes in waist circumference in both girls -0.21 (-0.37 to -0.05) and boys -0.23 (-0.35 to -0.11) after controlling for cardiorespiratory fitness. CONCLUSIONS: Our data support a unique role of muscle fitness in the promotion of metabolic health and prevention of excess adipose tissue accumulation in children.

The longitudinal relationship between motor competence and measures of fatness and fitness from childhood into adolescence.

OBJECTIVES: To examine longitudinal (seven years) relationships among cardiorespiratory fitness (VO2peak), body fatness, and motor competence. METHOD: Data were collected as part of the Copenhagen School Child Intervention Study (CoSCIS). Body fatness was assessed by the sum of four skinfolds. VO2peak was measured directly in a continuous running protocol. Motor competence was assessed using the Körperkoordinationtest für Kinder. This study used multilevel linear mixed models to evaluate the reciprocal longitudinal association between body fatness, VO2peak, and motor competence. All regressions were stratified by sex and adjusted by intervention and pubertal status. All variable coefficients were standardized. RESULTS: A reciprocal relationship was observed between children's motor competence with body fatness and VO2peak at the seven-year follow-up (6-13 years of age). Children with higher motor competence at baseline had a lower risk of having higher body fatness (ßboys=-0.45, 95% CI: -0.52 to -0.38; ßgirls=-0.35, 95% CI: -0.42 to -0.28) and higher VO2peak (ßboys=0.34, 95% CI: 0.27-0.40; ßgirls=0.27, 95% CI: 0.20-0.33) during childhood. Alternatively, higher body fatness or lower levels of VO2peak at baseline were associated with lower motor competence during childhood. CONCLUSIONS: These data suggest motor competence, body fatness, and VO2peak demonstrate reciprocal relationships across childhood (6-13 years of age). Interventions addressing motor competence, cardiorespiratory fitness, and body fatness in early childhood are recommended, as intervention effects are likely to be enhanced because of the mutual reciprocal associations between these three variables.

Associations Between Aerobic Fitness and Cognitive Control in Adolescents.

Previous research has found positive associations between cognitive control and aerobic fitness in preadolescents and adults; however, fewer studies have investigated these associations in adolescents. Adolescence is of particular interest due to continued maturation of the prefrontal cortex; an area that subserves cognitive control. This study investigated the associations of aerobic fitness and cognitive control in adolescents. An assessment of aerobic fitness (Andersen intermittent running test) and two tests of cognitive control were collected to investigate these associations. Participants completed a test of inhibitory control (flanker task) and a test of cognitive flexibility (switch task). Along with traditional measures of reaction time (RT) and accuracy, diffusion modeling was utilized to combine these measures to calculate latent variables (i.e., drift rate, boundary separation, and nondecision time). Associations between cognitive measures and fitness were assessed with linear regressions while controlling for potential confounding factors. Higher fitness was associated with shorter reaction time and higher accuracy in the flanker task, indicating better inhibitory control performance. In addition, greater aerobic fitness was associated with greater quality of information uptake in the flanker task, as indicated by drift rate. In the switch task, higher aerobic fitness was associated with greater accuracy and longer switch RT indicating a speed-accuracy tradeoff. Results from the switch task diffusion modeling supported this conclusion as indicated by greater fitness associated with greater boundary separation, or response conservativeness. Further, greater drift rate in the switch task was associated with greater fitness. These findings corroborate growing evidence indicating the importance of aerobic fitness for inhibitory control and cognitive flexibility. This study extends the literature by demonstrating these effects in a large sample of adolescents with a computational model of the mechanisms that underlie cognition.

Physical activity intensity, bout-duration, and cardiometabolic risk markers in children and adolescents.

OBJECTIVES: To determine the role of physical activity intensity and bout-duration in modulating associations between physical activity and cardiometabolic risk markers. METHODS: A cross-sectional study using the International Children's Accelerometry Database (ICAD) including 38,306 observations (in 29,734 individuals aged 4-18 years). Accelerometry data was summarized as time accumulated in 16 combinations of intensity thresholds (≥500 to ≥3000 counts/min) and bout-durations (≥1 to ≥10 min). Outcomes were body mass index (BMI, kg/m2), waist circumference, biochemical markers, blood pressure, and a composite score of these metabolic markers. A second composite score excluded the adiposity component. Linear mixed models were applied to elucidate the associations and expressed per 10 min difference in daily activity above the intensity/bout-duration combination. Estimates (and variance) from each of the 16 combinations of intensity and bout-duration examined in the linear mixed models were analyzed in meta-regression to investigate trends in the association. RESULTS: Each 10 min positive difference in physical activity was significantly and inversely associated with the risk factors irrespective of the combination of intensity and bout-duration. In meta-regression, each 1000 counts/min increase in intensity threshold was associated with a -0.027 (95% CI: -0.039 to -0.014) standard deviations lower composite risk score, and a -0.064 (95% CI: -0.09 to -0.038) kg/m2 lower BMI. Conversely, meta-regression suggested bout-duration was not significantly associated with effect-sizes (per 1 min increase in bout-duration: -0.002 (95% CI: -0.005 to 0.0005) standard deviations for the composite risk score, and -0.005 (95% CI: -0.012 to 0.002) kg/m2 for BMI). CONCLUSIONS: Time spent at higher intensity physical activity was the main determinant of variation in cardiometabolic risk factors, not bout-duration. Greater magnitude of associations was consistently observed with higher intensities. These results suggest that, in children and adolescents, physical activity, preferably at higher intensities, of any bout-duration should be promoted.