Effects of a school-based physical activity intervention on cardiometabolic health 5 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 5 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 (fourth and fifth grades). Follow-up assessment was conducted 5-year post-intervention (10th grade) where 180-210 (73%-85%) children provided valid data. Outcomes were CVD risk factors: triglyceride, total-to-high-density-lipoprotein-cholesterol ratio (TC:HDL ratio), insulin resistance, blood pressure (BP), waist circumference, and cardiorespiratory fitness (VO2peak ). Variables were analyzed individually and as a composite score through linear mixed models, including random intercepts for children. RESULTS: Analyses revealed significant sustained 5-year intervention effects for HDL (effect sizes [ES] = 0.22), diastolic BP (ES = 0.48), VO2peak (ES = 0.29), and composite risk score (ES = 0.38). These effects were similar to the immediate results following the intervention. In contrast, while TC:HDL ratio initially decreased post-intervention (ES = 0.27), this decrease was not maintained at 5-year follow-up (ES = 0.09), whereas WC was initially unchanged post-intervention (ES = 0.02), but decreased at 5-year follow-up (ES = 0.44). CONCLUSION: The significant effects of a 2-year school-based PA intervention remained for CVD risk factors 5 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.

The prospective association between objectively measured sedentary time, moderate-to-vigorous physical activity and cardiometabolic risk factors in youth: a systematic review and meta-analysis.

Sedentary time and moderate-to-vigorous physical activity (MVPA) may be uniquely related to cardiometabolic health. Excessive sedentary time is suggested as an independent cardiometabolic risk factor, while MVPA is favourably associated with cardiometabolic health. This systematic review and meta-analysis summarizes the evidence on a prospective relationship between objectively measured sedentary time, MVPA and cardiometabolic health indicators in youth. PubMed, Embase, CINAHL, PhyscINFO and SPORTDiscus were systematically searched from January 2000 until April 2018. Studies were included if sedentary time and physical activity were measured objectively and examined associations with body mass index, waist circumference, triglycerides, high-density lipoprotein, insulin, blood pressure or the clustering of these cardiometabolic risk factors. We identified 30 studies, of which 21 were of high quality. No evidence was found for an association between sedentary time and cardiometabolic outcomes. The association between MVPA and individual cardiometabolic risk factors was inconsistent. The meta-analysis for prospective studies found a small but significant effect size between MVPA at baseline and clustered cardiometabolic risk at follow-up (ES -0.014 [95% CI, -0.024 to -0.004]). We conclude that there is no prospective association between sedentary time and cardiometabolic health, while MVPA is beneficially associated with cardiometabolic health in youth.

Physical activity preferences of 10-year-old children and identified activities with positive and negative associations to cardiorespiratory fitness.

AIM: This study investigated children's physical activity (PA) preferences, as these can aid the design of school-based interventions. METHODS: Data were collected in 2014 as a part of the Active Smarter Kids study and 1026 students (52% boys) from 57 Norwegian primary schools completed a questionnaire about their favourite physical activities at a mean age of 10.2 ± 0.3 years. We identified five patterns of PA and studied whether gender, cardiorespiratory fitness and abdominal adiposity were associated with these patterns. RESULTS: Soccer and slalom skiing were the favourite activities, and the most pronounced gender differences were for activities favoured by girls, which included dancing, gymnastics, exercising to music and jumping rope (p < 0.001). When the five component patterns were analysed using linear mixed-effect models, this showed a strong female preference for dancing, gymnastics, exercising to music and climbing. Cardiovascular fitness was negatively associated with frisbee, dodgeball, baseball and floorball, and positively associated with team handball, volleyball and basketball and with slalom skiing and cross-country skiing. It was interesting that the children's preferences were not related to their abdominal adiposity. CONCLUSION: The results showed different gender-based PA preferences and positive and negative associations with cardiovascular fitness, but no relationship with abdominal adiposity.

Strong association between cardiorespiratory fitness and serum lipoprotein subclass pattern in prepubertal healthy children.

This study reveals the lipoprotein subclass pattern associated with cardiorespiratory fitness (CRF) in healthy children. Serum concentrations of lipoprotein subclasses and concentrations and average particle size of their main classes were quantified in 94 ethnic Norwegian children using high-performance liquid chromatography (HPLC). Twenty-four lipoprotein features were used as input to multivariate regression analysis with CRF measured either by peak oxygen consumption (VO2peak) using a continuous treadmill protocol or indirectly by the 10-minute Andersen intermittent running field test. By including BMI and gender as descriptors, a predictive cross-validated multivariate regression model was obtained for both CRF measures. CRF correlated positively with average particle size for high-density lipoprotein (HDL) and its subclasses of large HDL particles and negatively with very small HDL particles, chylomicrons, triglycerides, and average size and concentration of very low-density lipoprotein (VLDL) particles and VLDL subclasses of large particles (P<.05). BMI correlated negatively with both measures of CRF, but exhibited a stronger association with VO2peak than with the Andersen test. Our data showed a strong association between CRF measured either by VO2peak or by the Andersen test and a subclass lipoprotein pattern that is associated with cardiovascular (CV) health. Thus, our results show why high levels of CRF are beneficial for children's CV health. The Andersen test, being a practical field test that involves minimal equipment and, being less influenced by BMI than VO2peak, represents a good measure of CRF, and, accordingly, a proxy measure of cardiovascular health status in children.

The Andersen aerobic fitness test: New peak oxygen consumption prediction equations in 10 and 16-year olds.

Measurement of aerobic fitness by determining peak oxygen consumption (VO2peak ) is often not feasible in children and adolescents, thus field tests such as the Andersen test are required in many settings, for example in most school-based studies. This study provides cross-validated prediction equations for VO2peak based on the Andersen test in 10 and 16-year-old children. We included 235 children (n = 113 10-year olds and 122 16-year olds) who performed the Andersen test and a progressive treadmill test to exhaustion to determine VO2peak . Joint and sex-specific prediction equations were derived and tested in 20 random samples. Performance in terms of systematic (bias) and random error (limits of agreement) was evaluated by means of Bland-Altman plots. Bias varied from -4.28 to 5.25 mL/kg/min across testing datasets, sex, and the 2 age groups. Sex-specific equations (mean bias -0.42 to 0.16 mL/kg/min) performed somewhat better than joint equations (-1.07 to 0.84 mL/kg/min). Limits of agreement were substantial across all datasets, sex, and both age groups, but were slightly lower in 16-year olds (5.84-13.29 mL/kg/min) compared to 10-year olds (9.60-15.15 mL/kg/min). We suggest the presented equations can be used to predict VO2peak from the Andersen test performance in children and adolescents on a group level. Although the Andersen test appears to be a good measure of aerobic fitness, researchers should interpret cross-sectional individual-level predictions of VO2peak with caution due to large random measurement errors.

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 (VO2peak ). 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 VO2peak (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.

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.

Validity of noninvasive composite scores to assess cardiovascular risk in 10-year-old children.

Agreement between and classification accuracy of six different noninvasive composite scores and a cardiovascular disease (CVD) risk factor score were investigated in 911 (466 boys and 445 girls) 10-year-old Norwegian children. A CVD risk factor score (triglyceride, total cholesterol/HDL ratio, homeostasis model assessment of insulin resistance, systolic blood pressure (SBP), waist-to-height ratio (WHtR), and cardiorespiratory fitness) and six noninvasive risk scores (fitness+three different measurements of fatness (body mass index (BMI), WHtR, and skinfolds), with and without inclusion of SBP) were calculated (mean z-score by gender). Agreement was assessed using Bland-Altman plots. The ability of noninvasive scores to correctly classify children with clustered CVD risk was examined by receiver operating characteristic (ROC) analysis and Cohen's kappa coefficient (κ). For both sexes, the noninvasive scores without SBP showed excellent AUC values (AUC=0.93-0.94, 95% CI=0.88-0.98) and moderate kappa values (κ=0.49-0.64) and had limits of agreement of 0.0±0.78-0.89 (arbitrary unit). Inclusion of SBP increased AUC values (AUC=0.96-0.97, 95% CI=0.94-0.99), kappa values (κ=0.58-0.69), and reduced limits of agreement (0.0±0.68-0.76). Noninvasive scores that include fitness and fatness provide acceptable agreement and classification accuracy, allowing for widespread early identification of children that might be at risk for developing CVD later in life. SBP should be included in the noninvasive score to improve classification accuracy if possible.

Reference values for and cross-validation of time to exhaustion on a modified Balke protocol in Norwegian men and women.

The aims of the present study were to provide reference values for time to exhaustion (TTE) on a modified Balke treadmill protocol, and to perform a cross-validation of TTE as a measure of maximal oxygen consumption (VO2max ), in Norwegian men and women 20-85 years of age. Reference values for TTE were derived from a national sample of 765 subjects. An additional sample of 119 subjects was included in the cross-validation (total n = 884), where prediction equations for VO2max was established. A decline in TTE was seen with increased age. Prediction of VO2max in an independent dataset (n = 319) resulted in a R2  = 0.78 and standard error of the estimate = 4.55 mL/kg/min. The observed-predicted bias was small (mean difference <1.24 mL/kg/min), whereas random error was considerable (95% limits of agreement ± 7.11-9.70 mL/kg/min) across age in both men and women. Despite limitations concerning the prediction of VO2max on an individual level, TTE from the Balke protocol is a good measure of aerobic fitness in adults across a range of settings, and could be evaluated according to the suggested reference values.

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.

Effects of a 2-year school-based daily physical activity intervention on cardiorespiratory fitness: the Sogndal school-intervention study.

The aim of this study was to describe changes in children's cardiorespiratory fitness (CRF) following a school-based physical activity (PA) intervention. In total, 259 children (age 9.3 ± 0.3 years) were invited to participate, of whom 256 participated. The children from the intervention school (63 boys, 62 girls) carried out 60-min PA over 2 school years. The children from the control school (62 boys, 69 girls) had the regular curriculum-defined amount of physical education in school, i.e. 45 min twice weekly. One hundred and eighty-eight children (73.4%) successfully completed both the baseline and the post-intervention peak oxygen uptake (VO2 peak) test. VO2 peak was measured directly during a continuous progressive treadmill protocol where the children ran until exhaustion. The children from the intervention school increased their mean VO2 peak (95% confidence interval) 3.6 (2.5-4.6) mL/kg/min more than the children from the control school. This VO2 peak value was adjusted for both sex and baseline VO2 peak. Boys and girls demonstrated similar VO2 peak responses. The intervention, primarily carried out at a moderate intensity, had the biggest impact in children with low initial CRF levels. In conclusion, a 2-year school-based 60-min daily PA intervention significantly improved CRF in children.

Cardiovascular risk factor clustering and its association with fitness in nine-year-old rural Norwegian children.

This paper describes cardiovascular disease (CVD) risk factor levels in a population-representative sample of healthy, rural Norwegian children and examines the association between fitness and clustering of CVD risk factors. Final analyses included 111 boys and 116 girls (mean age 9.3+/-0.3). To determine the degree of clustering, six CVD risk factors were selected: homeostasis model assessment score, waist circumference, triglycerides, systolic blood pressure, total cholesterol to high-density lipoprotein ratio and fitness (VO2peak). Clustering was observed in 9.9% of the boys and 13.8% of the girls. In a different analysis, fitness was omitted as a CVD risk factor and analyzed against the five remaining CVD risk factors. Low fitness was a strong predictor for clustering of CVD risk factors, and children in the least-fit quartile had significantly poorer CVD risk factor values than all of those in the other quartiles. Finally, subjects were cross-tabulated into different fat-fit groups. For both sexes, the unfit and overweight/obese group had a significantly higher CVD risk factor score than the fit and normal weight group. Clustering of CVD risk factors was present in this group of rural children. Low fitness, and low fitness and high fatness combined, were highly associated with a clustered CVD risk.

Secular trends in physical fitness in Danish adolescents.

It is important to monitor changes over time in aerobic fitness and obesity in order to target interventions when health deteriorates. We analyzed data from three population studies of adolescents carried out in 1983, 1997, and 2003. Participants were 1050 adolescents from the whole country of Denmark in 1983, 410 in 1997, and 418 in 2003, the two latter cohorts from the City of Odense. VO(2max) was estimated from maximal power output (MPO) in a cycle test with progressively increasing workload. Estimated VO(2max) for boys and girls was 52 and 41 mL/min/kg, respectively, both in 1983, 1997, and 2003 with no difference between the three cohorts. However, body mass index (BMI) increased 10% in the upper decentile of the distribution since 1983. MPO decreased over time, but validation studies showed that this was not due to decreased VO(2max) . The cohort from 1983 was tested twice by school teachers and experienced scientists, and the scientists found higher MPO than school teachers in the same subjects, which emphasize the importance of good validation studies.

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.

Determinants of erythropoietin release in response to short-term hypobaric hypoxia.

We measured blood erythropoietin (EPO) concentration, arterial O(2) saturation (Sa(O(2))), and urine PO(2) in 48 subjects (32 men and 16 women) at sea level and after 6 and 24 h at simulated altitudes of 1,780, 2,085, 2,454, and 2,800 m. Renal blood flow (Doppler) and Hb were determined at sea level and after 6 h at each altitude (n = 24) to calculate renal O(2) delivery. EPO increased significantly after 6 h at all altitudes and continued to increase after 24 h at 2,454 and 2,800 m, although not at 1,780 or 2,085 m. The increase in EPO varied markedly among individuals, ranging from -41 to 400% after 24 h at 2,800 m. Similar to EPO, urine PO(2) decreased after 6 h at all altitudes and returned to baseline by 24 h at the two lowest altitudes but remained decreased at the two highest altitudes. Urine PO(2) was closely related to EPO via a curvilinear relationship (r(2) = 0.99), although also with prominent individual variability. Renal blood flow remained unchanged at all altitudes. Sa(O(2)) decreased slightly after 6 h at the lowest altitudes but decreased more prominently at the highest altitudes. There were only modest, albeit statistically significant, relationships between EPO and Sa(O(2)) (r = 0.41, P < 0.05) and no significant relationship with renal O(2) delivery. These data suggest that 1) the altitude-induced increase in EPO is "dose" dependent: altitudes > or =2,100-2,500 m appear to be a threshold for stimulating sustained EPO release in most subjects; 2) short-term acclimatization may restore renal tissue oxygenation and restrain the rise in EPO at the lowest altitudes; and 3) there is marked individual variability in the erythropoietic response to altitude that is only partially explained by "upstream" physiological factors such as those reflecting O(2) delivery to EPO-producing tissues.