Longitudinal changes in device-measured physical activity from childhood to young adulthood: the PANCS follow-up study

BACKGROUND

There is a lack of longitudinal studies examining changes in device-measured physical activity and sedentary time from childhood to young adulthood. We aimed to assess changes in device-measured physical activity and sedentary time from childhood, through adolescence, into young adulthood in a Norwegian sample of ostensibly healthy men and women.

METHODS

A longitudinal cohort of 731 Norwegian boys and girls (49% girls) participated at age 9 years (2005-2006) and 15 years (2011-2012), and 258 of these participated again at age 24 years (2019-2021; including the COVID-19 pandemic period). Physical activity and sedentary time were measured using ActiGraph accelerometers. Linear mixed models were used to analyse changes in physical activity and sedentary time and whether low levels of childhood physical activity track, i.e., persist into young adulthood (nchange=721; ntracking=640).

RESULTS

The most prominent change occurred between the ages of 9 to 15 years, with an increase in sedentary time (150 min/day) and less time spent in light (125 min/day), moderate (16 min/day), and vigorous physical activity (8 min/day). Only smaller changes were observed between the ages of 15 and 24 years. Changes in moderate-to-vigorous physical activity from childhood to young adulthood differed between subgroups of sex, tertiles of body mass index at baseline and tertiles of peak oxygen uptake at baseline. While the tracking models indicated low absolute stability of physical activity from childhood to young adulthood, children in the lowest quartiles of moderate-to-vigorous (OR:1.88; 95%CI: 1.23, 2.86) and total physical activity (OR: 1.87; 95%CI: 1.21, 2.87) at age 9 years were almost 90% more likely to be in these quartiles at age 24 years compared to those belonging to the upper three quartiles at baseline.

CONCLUSIONS

We found a substantial reduction in physical activity and increase in time spent sedentary between age 9 and 15 years. Contrary to previous studies, using mainly self-reported physical activity, little change was observed between adolescence and young adulthood. The least active children were more likely to remain the least active adults and could be targeted for early intervention.

Effects of a school-based physical activity intervention on cardiometabolic health five years after cessation

BACKGROUND

While there have been several school-based physical activity (PA) interventions targeting improvement in cardiovascular disease (CVD) risk factors, few have assessed long-term effects. The aim of this paper was therefore to determine intervention effects on CVD risk factors five years after cessation.

METHODS

Two schools were assigned to intervention (n=125) or control (n=134). The intervention school offered 210 min/week more PA than the control school over two consecutive years (4^th and 5^th grades). Follow-up assessment was conducted five-year post intervention (10^th grade) where 180-210 (73-85%) children provided valid data. Outcomes were CVD risk factors: triglyceride (TG), total-to-high-density-lipoprotein-cholesterol ratio (TC:HDL ratio), insulin resistance (HOMA), blood pressure (BP), waist circumference (WC), and cardiorespiratory fitness (VO_2peak ). Variables were analyzed individually and as a composite score through linear mixed models, including random intercepts for children.

RESULTS

Analyses revealed significant sustained five-year intervention effects for HDL (ES=.22), diastolic BP (ES=.48), VO_2peak (ES=.29), and composite risk score (ES=.38). These effects were similar to the immediate results following the intervention. In contrast, while TC:HDL ratio initially decreased post intervention (ES=.27), this decrease was not maintained at five-year follow-up (ES=.09), whereas WC was initially unchanged post intervention (ES=.02), but decreased at five-year follow-up (ES=.44).

CONCLUSION

The significant effects of a two-year school-based PA intervention remained for CVD risk factors five years after cessation of the intervention. As cardiometabolic health can be maintained long-term after school-based PA, this paper demonstrates the sustainability and potential of schools in the primary prevention of future CVD risk in children.

P5296A healthier lifestyle increases circulating pro-atrial natriuretic peptide concentrations in overweight children

Background

Higher concentrations of atrial natriuretic peptides (ANP) are associated with a poor prognosis among patients with cardiovascular disease (CVD). Counter-intuitively, higher ANP concentrations in healthy populations are associated with an ideal American Heart Association Cardiovascular Health score, which includes high level of physical activity, normal body mass index (BMI), optimal levels of lipids, blood pressure (BP) and glucose. Along this line, overweight individuals have lower than expected ANP concentrations, and it has been proposed that this natriuretic handicap could play a role in overweight related disorders. The mechanism behind the natriuretic handicap is still not clear, but presence of insulin resistance with hyperinsulinemia has been implicated.

Purpose

We investigated whether an intensive lifestyle intervention with an intended weight loss, including an increased level of physical activity and a healthy diet, could increase plasma concentrations of mid-regional pro-ANP (MR-proANP), a stable marker of ANP secretion, in overweight children. In a mechanistic perspective, we investigated metabolic changes associated with increases in MR-proANP concentrations.

Methods

This study is an extension of the Odense Overweight Intervention Study (OOIS) which included 99 overweight children (11–13 years, 55% girls). The children were randomised to a Day Camp Intervention Arm (DCIA) and a Standard Intervention Arm (SIA) for 6 weeks. DCIA included 3 hours physical activity per day and a healthy diet according to Danish recommendations. SIA included 1 weekly fun-based physical activity session and 1 lifestyle education session. OOIS included measurements of anthropometry, body composition, lipids, BP, glucose and insulin. Linear regression analyses, expressed as unstandardized regression coefficients, were used to examine between-group differences in MR-proANP concentrations and to examine the associations between changes in MR-proANP and variables of interest. As we wanted to study physiological relationships, we pooled both arms to one group to increase power in the latter.

Results

At week 6, children in DCIA had lower BMI (−2.4kg/m2) and lower total body fat (−6.5%) but higher level of fitness (4.1 ml/O2/min/kg) compared to children in SIA. From baseline to week 6 DCIA increased MR-proANP concentrations (B (95% CI): 5.7 (1.2 to 10.2) pmol/l, P=0.014) more than SIA. Of the variables studied, we found an inverse association between fall in insulin and increase in MR-proANP concentrations (B (95% CI): −0.52 (−1.02 to −0.02) pmol/l/mIU/ml, P=0.041). None of the other associations between changes in variables reached statistical significance.

Conclusion

A healthier lifestyle, based on a healthy diet and a higher level of physical activity, increases MR-proANP among overweight children. In a mechanistic perspective, improved insulin sensitivity with lower insulin appears to be a factor that leads to higher MR-proANP.

Acknowledgement/Funding

Trygfonden (Grant number: 7-11-0700)

Gender-specific effects of physical activity on children's academic performance: The Active Smarter Kids cluster randomized controlled trial

Active learning combines academic content with physical activity (PA) to increase child PA and academic performance, but the impact of active learning is mixed. It may be that this is a moderated relationship in which active learning is beneficial for only some children. This paper examine the impact of baseline academic performance and gender as moderators for the effects of active learning on children's academic performance. In the ASK-study, 1129 fifth-graders from 57 Norwegian elementary schools were randomized by school to intervention or control in a physical activity intervention between November 2014 and June 2015. Academic performance in numeracy, reading, and English was measured and a composite score was calculated. Children were split into low, middle and high academic performing tertiles. 3-way-interactions for group (intervention, control)∗gender (boys, girls)∗academic performance (tertiles) were investigated using mixed model regression. There was a significant, 3-way-interaction (p=0.044). Both boys (ES=0.11) and girls (ES=0.18) in the low performing tertile had a similar beneficial trend. In contrast, middle (ES=0.03) and high performing boys (ES=0.09) responded with small beneficial trends, while middle (ES=-0.11) and high performing girls (ES=-0.06) responded with negative trends. ASK was associated with a significant increase in academic performance for low performing children. It is likely that active learning benefited children most in need of adapted education but it may have a null or negative effect for those girls who are already performing well in the sedentary classroom. Differences in gendered responses are discussed as a possible explanation for these results.

TRIAL REGISTRATION

Clinicaltrials.gov registry, trial registration number: NCT02132494.

The effect of a two-year school-based daily physical activity intervention on a clustered CVD risk factor score-The Sogndal school-intervention study

To evaluate changes in clustered cardiovascular disease (CVD) risk factors in 9-year-old children following a 2-year school-based physical activity intervention. In total, 259 children (age 9.3 ± 0.3 years) were invited, of whom 256 participated. The intervention group (63 boys, 62 girls) carried out 60-minute teacher-controlled daily physical activity over two school years. The control group (62 boys, 69 girls) had the curriculum-defined amount of physical education (45 minutes twice each week). Of these, 67% (171 total, 91 intervention) successfully completed both baseline and post-intervention of six CVD risk factors: systolic blood pressure (SBP), triglyceride (TG), total cholesterol-to-high-density lipoprotein cholesterol ratio (TC:HDL ratio), waist circumference (WC), the homeostasis model assessment for insulin resistance (HOMA), and peak oxygen uptake (VO_2peak ). All variables were standardized by sex prior to constructing a cluster score (sum of z scores for all variables). The effect of the intervention on the cluster score was analyzed using linear multiple regression. The cluster score improved after the intervention (ES = .29). Furthermore, the analyses showed significant effects in favor of the intervention group for systolic blood pressure (ES = .35), total cholesterol-to-HDL-c ratio (ES = .23), triglyceride (ES = .40), and VO_2peak (ES = .57). A teacher-led school-based physical activity intervention that is sufficiently long and includes a substantial amount of daily physical activity can beneficially modify children's clustered CVD risk profile.

Validation of SenseWear Armband in children, adolescents, and adults

SenseWear Armband (SW) is a multisensor monitor to assess physical activity and energy expenditure. Its prediction algorithms have been updated periodically. The aim was to validate SW in children, adolescents, and adults. The most recent SW algorithm 5.2 (SW5.2) and the previous version 2.2 (SW2.2) were evaluated for estimation of energy expenditure during semi-structured activities in 35 children, 31 adolescents, and 36 adults with indirect calorimetry as reference. Energy expenditure estimated from waist-worn ActiGraph GT3X+ data (AG) was used for comparison. Improvements in measurement errors were demonstrated with SW5.2 compared to SW2.2, especially in children and for biking. The overall mean absolute percent error with SW5.2 was 24% in children, 23% in adolescents, and 20% in adults. The error was larger for sitting and standing (23%-32%) and for basketball and biking (19%-35%), compared to walking and running (8%-20%). The overall mean absolute error with AG was 28% in children, 22% in adolescents, and 28% in adults. The absolute percent error for biking was 32%-74% with AG. In general, SW and AG underestimated energy expenditure. However, both methods demonstrated a proportional bias, with increasing underestimation for increasing energy expenditure level, in addition to the large individual error. SW provides measures of energy expenditure level with similar accuracy in children, adolescents, and adults with the improvements in the updated algorithms. Although SW captures biking better than AG, these methods share remaining measurements errors requiring further improvements for accurate measures of physical activity and energy expenditure in clinical and epidemiological research.

Cross-sectional and prospective associations between physical activity, body mass index and waist circumference in children and adolescents

Objective

To study the cross‐sectional and prospective associations between physical activity (PA) of different intensities, body mass index (BMI) and waist circumference (WC) in children and adolescents using isotemporal substitution modelling.

Methods

Physical activity (accelerometry), BMI and WC were assessed in 6‐ (n = 970), 9‐ (n = 2,423) and 15‐year‐olds (n = 1,544) in 2005/2006 and 2011/2012. Participants aged 9 years in 2005/2006 were followed prospectively to 2011/12 (age 15). Associations between PA of different intensities (light, moderate and vigorous), BMI and WC were examined using isotemporal substitution models.

Results

Substituting 10 min per day of sedentary time with light PA was associated with higher WC (0.17 to 0.29 cm, p ≤ 0.003)) in all age groups. Substituting 10 min per day of sedentary time with moderate PA was associated with lower WC in 6‐ and 9‐year‐olds (−0.32 to −0.47 cm, p ≤ 0.013)). Substituting 10 min per day of sedentary time with vigorous PA was associated with lower WC in 9‐ and 15‐year‐olds (−1.08 to −1.79 cm, p ≤ 0.015)). Associations were similar with BMI as the outcome. In prospective analyses, substituting sedentary time with light, moderate or vigorous PA at age 9 was not associated with BMI or WC at age 15.

Conclusion

Substituting sedentary time with moderate PA appears favourably associated with adiposity in children, whereas vigorous PA may be required in adolescents. Cross‐sectional associations were not replicated in prospective analyses.

Motor competence and cardiorespiratory fitness have greater influence on body fatness than physical activity across time

We investigated the longitudinal associations among physical activity (PA), motor competence (MC), cardiorespiratory fitness (VO_2peak ), and body fatness across 7 years, and also analyzed the possible mediation effects of PA, MC, and VO_2peak on the relationships with body fatness. This was a seven-year longitudinal study with three measuring points (mean ages [in years] and respective sample size: 6.75±0.37, n=696; 9.59±1.07, n=617; 13.35±0.34, n=513). PA (moderate-to-vigorous PA-MVPA and vigorous PA-VPA) was monitored using accelerometers. MC was assessed by the "Körperkoordinationstest für Kinder-KTK" test battery. VO_2peak was evaluated using a continuous running protocol until exhaustion. Body fatness was determined by the sum of four skinfolds. Structural equation modeling was performed to evaluate the longitudinal associations among PA, MC, VO_2peak, and body fatness and the potential mediation effects of PA, MC, and VO_2peak . All coefficients presented were standardized (z-scores). MC and VO_2peak directly influenced the development of body fatness, and VO_2peak mediated the associations between MVPA, VPA, MC, and body fatness. MC also mediated the associations between MVPA, VPA, and body fatness. In addition, VO_2peak had the largest total association with body fatness (β=-0.431; P<.05), followed by MC (β=-0.369; P<.05) and VPA (β=-0.112; P<.05). As PA, MC, and VO_2peak exhibited longitudinal association with body fatness, it seems logical that interventions should strive to promote the development of fitness and MC through developmentally appropriate physical activities, as the synergistic interactions of all three variables impacted body fatness.

The association between angiogenic markers and fetal sex: Implications for preeclampsia research

OBJECTIVE

Current research suggests sexual dimorphism between the male and female fetoplacental units, but with unknown relevance for preeclampsia. We investigated the association between fetal sex and concentrations of the angiogenic markers soluble Fms-like kinase 1 (sFlt-1), placental growth factor (PlGF), and sFlt-1/PlGF ratio in first and second-third trimester in women with/without preeclampsia, and the impact of fetal sex on the prognostic value of angiogenic markers for preeclampsia.

STUDY DESIGN

Observational study in a prospective, population-based cohort of 2110 singleton pregnancies with 150 preeclampsia cases.

RESULTS

Higher sFlt-1 concentrations were observed for women carrying female fetuses in first trimester (all, 1107.65 vs. 992.27pg/ml; preeclampsia cases, 1118.79 vs. 934.49pg/ml, p<0.05) and in second-third trimester (all, 1130.03 vs. 1043.15pg/ml; preeclampsia, 1480.30 vs. 1152.86pg/ml, p<0.05), with similar findings for the sFlt-1/PlGF ratio concentrations in first (29.67 vs. 27.39 p<0.05) and second-third trimester (3.56 vs. 3.22, p<0.05). In first trimester, log transformed concentrations of PlGF, sFlt-1 and sFlt-1/PlGF (all participants) and sFlt-1 (preeclampsia cases) associated with fetal sex in adjusted analyses (p<0.05). In second-third trimester, only log(sFlt-1) associated with fetal sex (all, p=0.028; preeclampsia, p=0.067) In receiver operating curve analysis, prediction of early-onset preeclampsia by sFlt-1/PlGF tended to be superior in pregnancies with female vs. male fetuses (p=0.06).

CONCLUSION

Sexual dimorphism was observed for concentrations of angiogenic markers. Female fetal sex was associated to higher sFlt-1 and sFlt-1/PlGF ratio concentrations in both healthy pregnancies and women developing preeclampsia. Fetal sex should be considered in research and clinical use of angiogenic markers.

Longitudinal influence of musculo-skeletal injuries and extra physical education on physical fitness in schoolchildren

The aims of this study were to investigate if (A) injuries and (B) increased physical education (PE) influenced the development of physical fitness in schoolchildren. Simultaneously, to investigate if a possible PE effect was modified by sport participation outside school hours. This was a longitudinal controlled school-based study. Six schools with 270 min of PE (extra PE) and four schools with 90 min of PE were followed up for 2.5 years. In total, 1054 children were included for analysis (normal PE = 443, extra PE = 611). Development in fitness was analyzed using composite z-scores from six fitness tests measured four times. Information of injury and sport was derived from weekly automated mobile phone text messages surveying the presence of musculo-skeletal pain and organized sport participation. Injury and extra PE both influenced the development of physical fitness. Injury decreased development of physical fitness with -1.01 composite z-score units (95% CI: -1.57; -0.45). Extra PE increased physical fitness development with 0.80 (95% CI: 0.49; 1.10) composite z-score units. The influence of injury was not dependent on extra PE. No modifying effect was found by mean weekly sport participation outside school hours. In conclusion, extra PE had a positive effect, whereas injuries had a negative effect on physical fitness development in schoolchildren.

Maternal 25-hydroxyvitamin D level and fetal bone growth assessed by ultrasound: a systematic review

OBJECTIVES

To assess systematically the role of maternal vitamin D levels in fetal bone growth.

METHODS

PubMed, EMBASE and Cochrane databases were searched using the search words [Vitamin D] in combination with [fetal, fetus, intrauterine, or prenatal AND growth, development, bone, femur, or humerus]; [crown-rump length]; or [ultrasonography, prenatal]. Criteria for inclusion in this systematic review were data on maternal serum 25-hydroxyvitamin D (25(OH)D) during pregnancy and measurement of fetal growth by ultrasound.

RESULTS

We identified 750 publications initially, from which five observational studies were selected for inclusion in the final review. The parameters studied were humerus length (HL) and femur length (FL) and their Z-scores, femoral volume, femoral distal metaphyseal cross-sectional area (CSA), femoral proximal metaphyseal diameter (PMD), femoral mid-shaft diameter and crown-rump length. In one study, 25(OH)D was associated directly with FL; in another study 25(OH)D only correlated with FL and HL Z-scores when calcium intake was insufficient. Two studies found no association between 25(OH)D and FL, but detected a direct association with femoral PMD, and an inverse relation with femoral distal metaphyseal CSA, respectively.

CONCLUSIONS

Observational studies investigating the role of maternal vitamin D levels in fetal bone growth are sparse. Their evidence suggests that low maternal 25(OH)D levels may affect fetal bone growth under certain circumstances, especially in cases of simultaneous low calcium intake. Further studies are necessary.

Associations between bicycling and carotid arterial stiffness in adolescents: The European Youth Hearts Study

The aim of the study was to investigate the associations between bicycling and carotid arterial stiffness, independent of objectively measured moderate-and-vigorous physical activity. This cross-sectional study included 375 adolescents (age 15.7 ± 0.4 years) from the Danish site of the European Youth Heart Study. Total frequency of bicycle usage was assessed by self-report, and carotid arterial stiffness was assessed using B-mode ultrasound. After adjusting for pubertal status, body height, and objectively measured physical activity and other personal lifestyle and demographic factors, boys using their bicycle every day of the week displayed a higher carotid arterial compliance {standard beta 0.47 [95% confidence interval (CI) 0.07-0.87]} and distension [standard beta 0.38 (95% CI -0.04 to 0.81)]. Boys using their bicycle every day of the week furthermore displayed a lower Young's elastic modulus [standard beta -0.48 (95% CI -0.91 to -0.06)]. Similar trends were observed when investigating the association between commuter bicycling and carotid arterial stiffness. These associations were not observed in girls. Our observations suggest that increasing bicycling in adolescence may be beneficial to carotid arterial health among boys.

Parity and tanned white skin as novel predictors of vitamin D status in early pregnancy: a population-based cohort study

CONTEXT

In pregnancy, vitamin D insufficiency and deficiency, defined as serum 25-hydroxyvitamin D (25(OH)D) <50 nM, and <25 nM, respectively, may have adverse effects for both mother and child. Prevalence estimates, and identification of subgroups at special risk, may be useful for the planning of preventive strategies.

OBJECTIVE

To study the prevalence and risk factors of hypovitaminosis D in early pregnancy.

DESIGN AND METHODS

In a cross-sectional study of 1348 women in early pregnancy from the Odense Child Cohort, Denmark, 25(OH)D was determined and correlated to demographic and lifestyle variables (age, nationality, skin tone, parity, prepregnancy body mass index (BMI), smoking and sun exposure), using multiple linear and logistic regression analyses for all year, or stratified for summer and winter. The risk of vitamin D insufficiency was expressed as odds ratios (OR) with 95% confidence intervals in brackets.

RESULTS

The prevalence of vitamin D insufficiency and deficiency was estimated to 27·8% and 3·5% respectively. In adjusted analyses, vitamin D insufficiency was directly associated with winter season, OR = 1·89 (1·35-2·63); increasing prepregnancy BMI, OR = 1·06 (1·03-1·10); and smoking, OR = 2·7 (1·34-5·41); but was less frequent in nulliparous, OR = 0·47 (0·33-0·68) and tanned Caucasians, OR = 0·63 (0·41-0·97). Season-specific associations having parental origin from outside Europe in summer, OR = 4·13 (1·41-12·13); in winter smoking, OR = 3·15 (1·19-8·36); and prepregnancy BMI, OR = 1·12 (1·06-1·18).

CONCLUSIONS

Vitamin D insufficiency was widespread in early pregnancy. Associations to smoking, prepregnancy BMI and origin outside Europe varied with season. Multiparity and not being tanned in Caucasians represent new risk factors of vitamin D insufficiency.

Association between sweet drink intake and adiposity in Danish children participating in a long-term intervention study

BACKGROUND

In some previous studies direct associations between intake of soft drinks, sugar-sweetened beverages and adiposity have been reported. The majority of these studies were, however, conducted in the USA and it is uncertain if the results are applicable to non-US countries.

OBJECTIVE

To assess the association between sweet drink intake at age 6 and 9 years and the subsequent 3- to 7-year changes in body mass index (BMI) and sum of four skin-folds (Σ4SF).

METHODS

Information on sweet drink intake (7 days food record) and physical activity (accelerometer) was obtained at age 6 years (n = 366) [Correction made here after initial online publication.] and 9 years (n = 269). Weight, height and Σ4SF were measured at age 6, 9 and 13 years. Additional information on socio-economic status, maternal BMI and pubertal status was obtained.

RESULTS

No associations were observed between sweet drink intake at age 6 years and change in BMI or logΣ4SF from age 6 to 9 years or 6 to 13 years. Also, no associations were observed between change in sweet drink intake from age 6 to 9 years and subsequent change in BMI or logΣ4SF from age 9 to 13 years. A weak direct association was observed between sweet drink intake at age 9 years and change in logΣ4SF from age 9 to 13 years (per 100 g ∼ 3.38 fl oz) (β: 0.014, 95% confidence interval [CI]: -0.001 to 0.029, P = 0.06), while no association was seen for BMI. In supplementary analyses a similar association was observed for soft drinks (β: 0.087, 95% CI: 0.048 to 0.126, P = 0.001) but only in the intervention group.

CONCLUSION

We observed associations between intake of sweet drinks and soft drinks and change in skin-fold thickness in a group of Danish children. However, as the associations did not remain significant when multiple testing was considered or was only significant among children from the intervention group, the results do not confirm or refute the direct association reported in previous studies.

Adverse metabolic risk profiles in Greenlandic Inuit children compared to Danish children

OBJECTIVE

During recent decades, the prevalence of metabolic morbidity has increased rapidly in adult Greenlandic Inuit. To what extent this is also reflected in the juvenile Inuit population is unknown. The objective was, therefore, in the comparison with Danish children, to evaluate metabolic profiles in Greenlandic Inuit children from the capital in the southern and from the northern most villages

DESIGN AND METHODS

187 Inuit and 132 Danish children were examined with anthropometrics, pubertal staging, fasting blood samples, and a maximal aerobic test.

RESULTS

Both Inuit children living in Nuuk and the northern villages had significantly higher glucose, total cholesterol, apolipoprotein A1 levels, and diastolic blood pressure compared with Danish children after adjustment for differences in adiposity and aerobic fitness levels. The Inuit children living in Nuuk had significantly higher BMI, body fat %, HbA1 c, and significantly lower aerobic fitness and ApoA1 levels than northern living Inuit children.

CONCLUSIONS

Greenlandic Inuit children had adverse metabolic health profile compared to the Danish children, the differences where more pronounced in Inuit children living in Nuuk. The tendencies toward higher prevalence of diabetes and metabolic morbidity in the adult Greenlandic Inuit population may also be present in the Inuit children population.

The effects of physical activity and exercise on brain-derived neurotrophic factor in healthy humans: A review

The purpose of this study was to summarize the effects of physical activity and exercise on peripheral brain-derived neurotrophic factor (BDNF) in healthy humans. Experimental and observational studies were identified from PubMed, Web of Knowledge, Scopus, and SPORT Discus. A total of 32 articles met the inclusion criteria. Evidence from experimental studies suggested that peripheral BDNF concentrations were elevated by acute and chronic aerobic exercise. The majority of the studies suggested that strength training had no influence on peripheral BDNF. The results from most observational studies suggested an inverse relationship between the peripheral BDNF level and habitual physical activity or cardiorespiratory fitness. More research is needed to confirm the findings from the observational studies.

Aerobic capacity related to cardiac size in young children

AIM

Aerobic capacity, defined as peak oxygen uptake (VO2PEAK), is generally considered to be the best single marker for aerobic fitness. We assessed if VO2PEAK is related to different cardiac dimensions in healthy young children on a population base.

METHODS

In a cross-sectional study, 245 children (137 boys and 108 girls) aged 8-11 years, were recruited from a population based cohort. VO2PEAK (ml/min-1/kg-1) was assessed by indirect calorimetry during a maximal exercise test. DXA-scan was used to measure lean body mass (LBM) and total fat mass (TBF). Echocardiography, with 2-dimensional guided M-mode, was performed in accordance with current guidelines. Left ventricular end-diastolic diameter (LVDD) and left atrial end-systolic diameter (LA) were measured, and left ventricular mass (LVM) was calculated.

RESULTS

Univariate correlations were found between VO2PEAK versus LVDD r=0.44 and LA r=0.27 (both P<0.05) and LVM r=-0.06 (NS) in boys. Corresponding values for girls were; 0.55, 0.34 (both P<0.05) and 0.11 (NS). Multiple regression analysis with VO2PEAK as dependent variable and inclusion of LBM, TBF, sex, age, Tanner stage, and maximal heart rate as independent variables showed that 67% of the total variance of VO2PEAK could be explained by these variables. Including LVDD or LA in the model, added 1% additional explained variance.

CONCLUSION

Findings from this population based cohort of young healthy children show that multiple cardiac dimensions at rest are related to VO2PEAK. However, the different cardiac dimensions contributed very little to the added explained variance of VO2PEAK.

Importance of epoch length and registration time on accelerometer measurements in younger children

AIM

The aim of this study was to investigate the effect of epoch length on accumulation of minutes of physical activity per day over a spectrum of intensities, and the effect that selection of number of hours of acceptable registration required per day had on number of days that were considered acceptable.

METHODS

Participants were 696 children (369 boys and 327 girls) aged 6.7±0.4 yrs, from a population-based cohort. Physical activity was assessed by the Actigraph accelerometer for four days.

RESULTS

Main findings were that epoch length had a profound impact on accumulation of minutes of physical activity per day for higher intensities, whereas it had no effect on mean counts per minute. The chosen number of hours for an acceptable registration per day heavily influenced the number of days that were considered acceptable.

CONCLUSION

The findings in the present investigation should be taken into consideration when planning objective measurements of daily physical activity in younger children, and highlight the need for setting international recommendations for physical activity measurements with accelerometers, if different studies are to be comparable.

Effect of school-based interventions on physical activity and fitness in children and adolescents: a review of reviews and systematic update

BACKGROUND

School-based interventions are thought to be the most universally applicable and effective way to counteract low physical activity (PA) and fitness although there is controversy about the optimal strategy to intervene.

OBJECTIVES

The objective of this review was to summarise recent reviews that aimed to increase PA or fitness in youth and carry out a systematic review of new intervention studies.

METHODS

Relevant systematic reviews and original controlled and randomised controlled school-based trials with a PA or fitness outcome measure, a duration of ≥12 weeks, a sufficient quality and involvement of a healthy population aged 6-18 years that were published from 2007 to 2010 were included. Results In these reviews, 47-65% of trials were found to be effective. The effect was mostly seen in school-related PA while effects outside school were often not observed or assessed.

CONCLUSIONS

The school-based application of multicomponent intervention strategies was the most consistent, promising strategy, while controversy existed regarding the effectiveness of family involvement, focus on healthy populations at increased risk or duration and intensity of the intervention. All 20 trials in the review update showed a positive effect on in-school, out-of-school or overall PA, and 6 of 11 studies showed an increase in fitness. Taking into consideration both assessment quality and public health relevance, multicomponent approaches in children including family components showed the highest level of evidence for increasing overall PA. This review confirms the public health potential of high quality, school-based PA interventions for increasing PA and possibly fitness in healthy youth.

NOS3 variants, physical activity, and blood pressure in the European Youth Heart Study

BACKGROUND

In this study, we examined the influence of genetic variation in NOS3 on resting blood pressure (BP) in children and adolescents from the European Youth Heart Study (EYHS). Because the NOS3 gene expression is altered by physical activity (PA), we also tested for interaction between habitual PA and NOS3 variants on BP.

METHODS

A cross-sectional, random sample of 8-10-year old children (n = 1,214) and 14-16-year old adolescents (n = 1,141) from Denmark and Estonia were genotyped for four NOS3 tagging polymorphisms (rs1800783, rs1799983 (Glu298Asp), rs3918227, rs743507). PA was measured objectively using a hip-mounted accelerometer and through self-reported bicycling and TV-viewing. Permutation testing was used to correct for multiple testing, yielding an α level of 0.006.

RESULTS

Glu298Asp showed age-group-dependent associations with BP. In adolescents, Asp298 allele homozygotes had 0.19 s.d. (95% confidence interval (CI): 0.06; 0.13, P = 0.004) higher diastolic BP (DBP) and 0.25 s.d. (95% CI: 0.05; 0.46, P = 0.015) higher systolic BP (SBP), compared to Glu298 allele carriers. None of the three other single-nucleotide polymorphisms (SNPs) were associated with BP in adolescents. In children, none of the SNPs were associated with BP. No evidence of interaction between Glu298Asp and objectively measured PA was observed. Both self-reported bicycling and TV-viewing nominally modified the association between Glu298Asp and BP in adolescents (P < 0.05), the genetic effect being most apparent in inactive individuals. However, none of the interactions persisted after correcting for multiple testing.

CONCLUSIONS

The NOS3 Glu298Asp variant may associate with resting BP in adolescence but not in childhood, an effect that could be modified by PA.

Fat-free mass mediates the association between birth weight and aerobic fitness in youth

OBJECTIVE

To investigate whether birth weight acts as a biological determinant of later aerobic fitness, and whether fat-free mass may mediate this association.

METHODS

The European Youth Heart Study (EYHS) is a population-based cohort of two age groups (9 and 15 years) from Denmark, Portugal, Estonia and Norway. Children with parentally reported birth weight >1.5 kg were included (n = 2 749). Data were collected on weight, height, and skinfold measures to estimate fat mass and fat-free mass. Aerobic fitness (peak power, watts) was assessed using a maximal, progressive cycle ergometer test. Physical activity was collected in a subset (n = 1 505) using a hip-worn accelerometer and defined as total activity counts/wear time, all children with >600 minutes/day for ≥3 days of wear were included.

RESULTS

Lower birth weight was associated with lower aerobic fitness, after adjusting for sex, age group, country, sexual maturity and socio-economic status (ß = 5.4; 95% CI: 3.5, 7.3 W per 1 kg increase in birth weight, p < 0.001). When fat-free mass was introduced as a covariate in the model, the association between birth weight and aerobic fitness was almost completely attenuated (p = 0.7). Birth weight was also significantly associated with fat-free mass (ß = 1.4; 95% CI: 1.1, 1.8, p < 0.001) and fat-free mass was significantly associated with aerobic fitness (ß = 3.6; 95% CI: 3.4, 3.7, p < 0.001). Further adjustment for physical activity did not alter the findings.

CONCLUSION

Birth weight may have long-term influences on fat-free mass and differences in fat-free mass mediate the observed association between birth weight and aerobic fitness.

Linking definition of childhood and adolescent obesity to current health outcomes

OBJECTIVE

To evaluate the ability of body mass index (BMI) and fat location indices to predict clustering of risk factors for cardiovascular and metabolic disorders in children and adolescents.

METHODS

A total of 2 835 children in the 3(rd) (8.2-11.3 years) and 9(th) (14-17.3 years) grade were randomly selected from Denmark, Estonia and Portugal. BMI, waist-circumference (WC) and waist-to-height ratio (WHt) were evaluated. Children were considered to have clustering of risk factors if >or=3 risk factors were present: high levels of total cholesterol, triglyceride, glucose, insulin, blood pressure and low levels of aerobic fitness and HDL-C. The diagnostic accuracy for detecting children at risk was evaluated through receiver operating characteristics analyses, performed separately for boys and girls in the four age groups: 8.2-9.5; 9.5-11.3; 14.0-15.5 and 15.5-17.3 years. Cut-offs producing equal sensitivity and specificity and minimizing misclassifications were derived. Children were classified as overweight and obese based on BMI cut-offs producing equal sensitivity and specificity and minimizing misclassifications, respectively.

RESULTS

The diagnostic accuracy for identifying children at risk, measured by the area under the curve (AUC), of all anthropometric indices were significantly higher than what would be expected by chance (AUC >0.5). BMI cut-offs for overweight had similar sensitivity (58.8% to 75%) and specificity (60% to 71.2%) values, whereas specificity (94.4% to 99.7%) was markedly higher than sensitivity (9.3% to 52.6%) for obesity cut-offs.

CONCLUSION

BMI, WC and WHt can be used to identify children and adolescents aged 8.2-17.3 years with a clustering of cardiovascular risk factors.

Effects of a 2-year school-based daily physical activity intervention on cardiovascular disease risk factors: the Sogndal school-intervention study

The aim of this study was to investigate the effect of a 2-year school-based physical activity (PA) intervention in 9-year-old children on cardiovascular disease (CVD) risk factors. One intervention school (I-school) (n=125) and one control school (C-school) (n=131) were included. The children at the I-school carried out 60 min of PA daily. The PA lessons were planned, organized and led by expert physical education (PE) teachers. In the C-school, children were offered the normal 45 min of PE twice weekly. The intervention resulted in a greater beneficial development in systolic (P=0.003) and diastolic (P=0.002) blood pressure, total cholesterol-to-high-density lipoprotein cholesterol ratio (P=0.011), triglyceride (P=0.030) and peak oxygen uptake (P<0.001) in I-school children than in C-school children. No significant differences were observed in waist circumference, body mass index and the homeostasis model assessment for insulin resistance between the two groups. Furthermore, the intervention, primarily carried out at moderate intensity, had the strongest impact in children with the least favorable starting point. In conclusion, a daily school-based PA intervention can beneficially modify children's CVD risk profile if the intervention has sufficient duration and includes a substantial amount of daily PA, and if the PA is implemented by expert PE teachers.

Estimation of peak oxygen uptake from maximal power output among 9-10 year-old children in Lhasa, Tibet

AIM

The aims of the present study of Tibetan and Han Chinese children were to establish prediction equations for peak oxygen uptake (VO2peak) using conventional power output measures, and to compare with prediction models based on data from sea level.

METHODS

In 25 Tibetan children and 15 Han Chinese children aged 9-10 years, living in Lhasa at 3700 meters above sea level, VO2peak was measured directly using a portable oxygen analyzer, and predicted from maximal power output (Wmax) using a maximal cycle ergometer test.

RESULTS

In multiple regression analyses with VO2peak as dependent variable and Wmax and sex as covariates, a total adjusted R2 of 0.76 and 0.82 were found in Tibetan and Han Chinese children, separately. Sex made a unique, and statistically significant, contribution to the prediction of VO2peak. Three equations derived from sea level data were compared with the equations from the present study. None of the three could accurately predict the direct measured V.O2peak, and predictions differed in an unsystematic manner, including over- or underestimation and no differentiation between genders.

CONCLUSION

Peak oxygen uptake could be estimated from Wmax and sex in a progressive cycle ergometer test among children living at 3700 meters in Tibet. The estimate of VO2peak is probably more valid using the present equations than prediction models based on data from sea level. The equations used for the prediction are: Bianba(eqT): (l·min(-1)) = 0.5419 + (0.0096· Wmax) - (0.0562· sex); boys=0; girls=1 Bianba(eqH): (l·min(-1)) = 0.4060 + (0.0124· Wmax) - (0.1775· sex); boys=0; girls=1.

Parental, socio and cultural factors associated with adolescents' sports participation in four Danish municipalities

Despite the well-documented health effects of physical activity, few studies focus on the correlates of leisure-time sports and exercise participation. The present study examined correlations between adolescent sports participation and demographic factors, socioeconomic status (SES) and sociocultural factors. A school-based cross-sectional cluster sample including 6356 Danish fifth- and ninth-grade adolescents from four municipalities were included. Age (younger) and gender (boy) were associated with adolescents' sports participation. Girls were half as likely [odds ratio (OR) 0.49 95% confidence interval (CI): 0.44-0.55] to participate in sports than boys. Adolescents were more likely to participate in sports if they perceived their parents as active in exercise or sports. Adolescents with one or two unemployed parents were 0.75 (95% CI: 0.62-0.89) and 0.75 (95% CI: 0.56-1.00), respectively, less likely to participate in sports than adolescents with two employed parents. In a gender-stratified analysis, parents' occupational status was only a predictor of sports participation in girls. Differences between municipalities in adolescents' sports participation remained significant when controlled for individual factors such as gender, age, parents' background or parents' physical activity. The association between sociocultural and SES was stronger for girls than boys. In conclusion, demographics, SES and sociocultural factors were the best determinants of adolescent sport participation.

A 3-year longitudinal analysis of changes in fitness, physical activity, fatness and screen time

AIM

To analyse whether changes in physical activity index (PAI), screen time (ST: television, computer) and body mass index (BMI) made a contribution to longitudinal changes in fitness of children and adolescents. Additionally, we analysed the interaction between baseline fitness level and changes in fitness.

METHODS

This is a 3-year longitudinal study of 345 high school students aged 11-19 years. Students performed curl-ups, push-ups and 20-m shuttle run tests from Fitnessgram. PA and ST were evaluated using a standard questionnaire. Standardized scores of fitness tests were summed. Changes over time were calculated as Delta(1) (2007 minus 2006), Delta(2) (2008 minus 2007) and Delta(3) (2008 minus 2006).

RESULTS

Changes in PAI were positively and independently associated with changes in fitness in Delta(1), Delta(2) and Delta(3). Changes in BMI were negatively associated with changes in fitness in Delta(3). Participants highly fit at baseline were those who showed positive changes in PAI over Delta(3), decreased changes in ST and had the lowest increase in BMI over 3 years compared with those low-fit at baseline.

CONCLUSIONS

Changes in BMI were associated with changes in fitness over 3 years. However, changes in PAI were the best predictor for changes in fitness in each year and over the 3 years of evaluation in youth.

Objectively assessed physical activity and aerobic fitness in a population-based sample of Norwegian 9- and 15-year-olds

The present study described current physical activity, determined compliance with physical activity guidelines and assessed aerobic fitness in a nationally representative sample of 9- and 15-year-olds in Norway. In 2005-2006, 2299 children and adolescents were randomly recruited. The participation rate was 89% and 74% among the 9- and 15-year-olds, respectively. Physical activity was assessed objectively by accelerometry, and aerobic fitness was measured directly as peak oxygen uptake during a cycle ergometry test. Boys were more physically active than girls, and 9-year-olds were substantially more active than 15-year-olds. Physical activity was higher during weekdays than weekends, and 9-year-olds were most active during spring. While four out of five children met current physical activity guidelines, only half of the adolescents did. The mean (SD) values for peak VO2 were: 9-year-old boys, 48.2 (7.1) mL/min/kg; 9-year-old girls, 42.9 (6.7) mL/min/kg; and 15-year-old girls 41.1 (6.0) mL/min/kg and 15-year-old boys 51.9 (8.0) mL/min/kg. Because of the high participation rate, this study provides a good description of the physical activity and aerobic fitness in the young population. Finally, girls and adolescents seem appropriate targets when promoting physical activity in order to increase the proportion meeting the recommendations.

Cardiorespiratory fitness and body mass index values in 9-year-old rural Norwegian children

AIM

To describe cardiorespiratory fitness and body mass index (BMI) values in a representative population of 9-year-old Norwegian children in two rural communities and compare present values with previous findings.

METHODS

Two hundred and fifty-nine 9-year-old children were invited, and 256 participated in this study. Maximal oxygen uptake was directly measured during a continuous progressive treadmill protocol. Body mass and height were also measured.

RESULTS

The mean +/- SD relative maximal oxygen uptake was 52.8 +/- 6.5 for boys and 46.9 +/- 7.2 mL/kg/min for girls. Eight percent of the boys and 16.8% of the girls were classified as overweight, and 1.6% of the boys and 6.9% of the girls as obese. Mean age, body mass, height and Ponderal index were not significantly different between sexes. Girls had a higher BMI than boys (p = 0.05).

CONCLUSION

Compared to earlier Norwegian studies, children's BMI values seem to have increased substantially. This increase is most pronounced in girls. When assessing these differences using the PI, this increase is less marked. Comparing maximal oxygen uptake data with that in earlier Nordic studies, there is no evidence that fitness has declined among 9-year olds. However, the limitations of the few earlier studies make reliable comparisons difficult.

PPARGC1A sequence variation and cardiovascular risk-factor levels: a study of the main genetic effects and gene x environment interactions in children from the European Youth Heart Study

AIMS/HYPOTHESIS

The PPARGC1A gene coactivates multiple nuclear transcription factors involved in cellular energy metabolism and vascular stasis. In the present study, we genotyped 35 tagging polymorphisms to capture all common PPARGC1A nucleotide sequence variations and tested for association with metabolic and cardiovascular traits in 2,101 Danish and Estonian boys and girls from the European Youth Heart Study, a multicentre school-based cross-sectional cohort study.

METHODS

Fasting plasma glucose concentrations, anthropometric variables and blood pressure were measured. Habitual physical activity and aerobic fitness were objectively assessed using uniaxial accelerometry and a maximal aerobic exercise stress test on a bicycle ergometer, respectively.

RESULTS

In adjusted models, nominally significant associations were observed for BMI (rs10018239, p = 0.039), waist circumference (rs7656250, p = 0.012; rs8192678 [Gly482Ser], p = 0.015; rs3755863, p = 0.02; rs10018239, beta = -0.01 cm per minor allele copy, p = 0.043), systolic blood pressure (rs2970869, p = 0.018) and fasting glucose concentrations (rs11724368, p = 0.045). Stronger associations were observed for aerobic fitness (rs7656250, p = 0.005; rs13117172, p = 0.008) and fasting glucose concentrations (rs7657071, p = 0.002). None remained significant after correcting for the number of statistical comparisons. We proceeded by testing for gene x physical activity interactions for the polymorphisms that showed nominal evidence of association in the main effect models. None of these tests was statistically significant.

CONCLUSIONS/INTERPRETATION

Variants at PPARGC1A may influence several metabolic traits in this European paediatric cohort. However, variation at PPARGC1A is unlikely to have a major impact on cardiovascular or metabolic health in these children.

An intermittent running test to estimate maximal oxygen uptake: the Andersen test

AIM

Monitoring of height and weight in children in schools has been discussed to get data on trends in obesity. Physical fitness may be just as important to monitor and a simple reliable test will therefore be important. The aim of this paper was to analyze the association between VO2max measured during maximal work on a treadmill and running distance in an intermittent running test.

METHODS

Three different groups conducted an intermittent running test VO2max was measured directly during treadmill running. The groups were 27 physical education students (age 20.0-27.0 years), 57 children (age 9.9-11.0 years), and 14 male elite soccer players (age 14.2-15.0 years).

RESULTS

The reproducibility of the Andersen test was good (r=0.84). Subjects ran 15 m (SD 61 m) longer the second time, but this difference was not significant (P=0.102). The association between running distance in the Andersen test and VO2max measured on the treadmill showed a correlation coefficient of 0.87 in university students, 0.68 in children, and 0.60 in soccer players. For the whole group: VO2max= 18.38 + (0.03301*distance) - (5.92*sex) (boys=0;girls=1) (r=0.84).

CONCLUSION

The test may provide teachers and health care professionals with an important tool to estimate physical fitness in children and adolescents in a fast, non-expensive and reliable way.