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Søren Brage, Niels Wedderkopp, Lars Bo Andersen and Karsten Froberg

Four Computer Science and Applications (CSA, Model 7164) accelerometers were validated against speed and heart rate in a field trial, consisting of two walking and two preset running speeds, and 3 min of running at freely chosen speeds. Fifteen children (9–11 years) were recruited from a suburban school in Denmark. Mean CSA output was calculated and converted to acceleration by calibration to sinusoidal accelerations in a mechanical setup, the latter variable being independent of frequency-based filtering. Mean CSA output and estimated acceleration both correlated significantly with speed (r 2 = 0.55 and r 2 = 0.76, respectively) and heart rate (r 2 = 0.60 and r 2 = 0.81, respectively), controlled for gender. ANOVA post hoc test failed to show significant differences in accelerometer output between running speeds. Inter-individual variability of CSA output and acceleration could not be explained by differences in step frequency in walking but running values correlated significantly with step frequency (r = −0.86 and r = −0.47 for CSA output and acceleration, respectively). Conversion of CSA output to average acceleration provides more precise estimates of intensity with less inter-individual variability than raw CSA output. Different running intensities, however, are generally not well differentiated with vertical accelerometry.

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Niels Wedderkopp, Karsten Froberg, Henrik Steen Hansen, Chris Riddoch and Lars Bo Andersen

The aim of this study was to assess the association between physical fitness and clustering of cardiovascular disease (CVD) risk factors in boys and girls aged 9 years (children) and 15 years (adolescents). Subjects were 1020 randomly selected children and adolescents. Cardiorespiratory fitness was assessed by a maximal cycle ergometer test. A subject was defined as having a risk factor if he/she belonged to the upper quartile of risk within age and gender group for that risk factor. Clustering was analysed in relation to being at risk in a) three or more and b) four or more of five possible risk factors (TC:HDL ratio, insulin:glucose ratio, triglyceride, systolic BP and sum of four skinfolds. Physical fitness was weakly related to single CVD risk factors except sum of skinfolds where the relationship was strong. Low fitness increased the risk of having three or more CVD risk factors with odds ratios (OR) using the upper quartile of fitness as reference of 1.9 (95% CI: 0.8–4.1), 3.0 (95% CI: 1.4–6.3) and 11.4 (95% CI: 5.7–22.9), respectively. Using the criterion of four or more risk factors, an OR of 24.1 (95% CI 5.7–101.1) was found in the low fit group.

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Stig Eiberg, Henriette Hasselstrom, Vivian Grønfeldt, Karsten Froberg, Ashley Cooper and Lars Bo Andersen

The aim of this study was to investigate whether risk factors for cardiovascular disease cluster in 6- to 7-year-old children and whether low physical fitness is a predictor of risk factor clustering. The study included 369 boys (6.8 ± 0.4 years) and 327 girls (6.7 ± 0.4 years). VO2max was directly measured during a treadmill test. The ratio of total cholesterol to high-density cholesterol, triglyceride levels, the ratio of insulin to glucose, systolic blood pressure, and the sum of four skinfolds were selected as risk factors. A child was considered at risk for individual factors if he or she had values in the least favorable quartile. The number of children with more than three cardiovascular disease cluster risk factors was not significantly different from a binominal distribution. This lack of clustering could be a result of the fact that these young children have not yet developed insulin resistance. Children in the lowest quartile of fitness had an odds ratio of 2.1 (CI: 1.0–4.4) for having three or more risk factors compared with the most fit. This is interesting with regard to prevention because it indicates that an intervention involving increased physical activity might postpone or even prevent the development of risk factors.

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Søren E. Larsen, Henrik S. Hansen, Karsten Froberg and Jens Rokkedal Nielsen

This study investigated a group of young elite cyclists at the age of 19–20 years. The cardiac characteristics, left ventricular function and structure, after long-term and high intensity endurance training, were examined by echocardiography during resting conditions. In comparison with an age-matched control group, the elite cyclists had significantly lower systolic blood pressure, heart rate, and total body fat and a significantly higher physical fitness. Left ventricular mass, left ventricular mass indexed for differences in body size, and both systolic and diastolic dimensions of the left ventricle were increased significantly in the elite cyclist group. No significant difference was found in left ventricular function. Left ventricular diastolic function was examined (E/A-ratio, E = early passive, A = late active, atriale induced transmitral diastolic flow) and showed no significant difference between the two groups in spite of the structural changes observed in the left ventricular structure. We conclude that structural but not functional cardiac changes can be observed in elite cyclists when examined during resting conditions.

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Magnus Dencker, Bianca Hermansen, Anna Bugge, Karsten Froberg and Lars B. Andersen

This study investigated the predictors of aerobic fitness (VO2PEAK) in young children on a population-base. Participants were 436 children (229 boys and 207 girls) aged 6.7 ± 0.4 yrs. VO2PEAK was measured during a maximal treadmill exercise test. Physical activity was assessed by accelerometers. Total body fat and total fat free mass were estimated from skinfold measurements. Regression analyses indicated that significant predictors for VO2PEAK per kilogram body mass were total body fat, maximal heart rate, sex, and age. Physical activity explained an additional 4–7%. Further analyses showed the main contributing factors for absolute values of VO2PEAK were fat free mass, maximal heart rate, sex, and age. Physical activity explained an additional 3–6%.

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Russell Jago, Karsten Froberg, Ashley R. Cooper, Stig Eiberg and Lars Bo Andersen

Background:

It is not clear the extent to which change in adiposity and cardiovascular fitness (CRF) during early childhood are associated with change in cardiovascular risk factors or if associations are independent or interactive.

Methods:

383 Danish children were examined at ages 6 and 9. CRF, sum of skinfolds (SSF), and blood pressure were assessed. Fasting blood samples were used to calculate total cholesterol (TC), high and low density lipoprotein cholesterol (HDL-C & LDL-C), triglycerides, insulin, glucose, and HOMA-IR. Regression models examined whether CRF change or SSF change were independently or interactively associated with risk variables.

Results:

Change in SSF was independently associated with change in TC (z =4.83, P < .0o1), LDL-C (z =4.38, P < .001), systolic (z = 3.45, P < .001), and diastolic (z = 2.45, P = .014) blood pressure. CRF change was independently associated with change in TC (z =-3.86, P < .001), HDL-C (z =3.85, P < .001), and systolic blood pressure (z = 2.06, P = .040).

Conclusions:

Change in fitness and adiposity were independently associated with the development of cardiovascular risk factors among young children suggesting a need to increase CRF and prevent weight gain early during development to improve cardiovascular health.

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Lars Bo Andersen, Niels Wedderkopp, Peter Kristensen, Niels Christian Moller, Karsten Froberg and Ashley R. Cooper

Background:

Cycling to school may potentially increase physical activity level in sedentary children. Transport to school occur twice a day and could improve cardiovascular health in children. Commuter cycling is associated with lower mortality and cardiovascular disease rate in adults, but limited evidence exists in children.

Methods:

Participants were 334 children (age 9.7 ± 0.5 years) who were followed up 6 years later. Mode of travel to school was investigated by questionnaire. Cardiovascular (CVD) risk factors were compared by mode of travel to school both at baseline and at follow up and for subjects who changed mode of transportation. No difference was found between walkers and passive travelers, and these groups were merged in the analysis.

Results:

A consistent pattern of better CVD risk factor profile in commuter cyclists compared with children using other means of transport was found. Participants, who did not cycle to school at baseline, and who had changed to cycling at follow up, were fitter, had better cholesterol/HDL ratio, better glucose metabolism, and a lower composite CVD risk factor score than those who did not cycle at either time point.

Conclusion:

Cycling to school may contribute to a better cardiovascular risk factor profile in young people.

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Alison M. McMinn, Esther M.F. van Sluijs, Niels Wedderkopp, Karsten Froberg and Simon J. Griffin

Cross-sectional associations between sociocultural factors and objectively-measured physical activity in a sample of 397 children (aged 9) and 213 adolescents (aged 15) were investigated. Associations with children’s physical activity were found for mothers’ physical activity (β=80,p < .01), parental participation (β=67,p = .01), mother’s age (β=−8,p < .01) and, in girls, fathers’ physical activity (β=73, p = .045; R2 for final model: 10.6%). No sociocultural factors were significantly associated with adolescents’ physical activity. Parental factors might be important targets for interventions to increase children’s physical activity but other factors may have greater influence. For adolescents’ physical activity, factors from other domains may be more important to target.

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Lars Østergaard, Anders Grøntved, Line Anita B. Børrestad, Karsten Froberg, Michael Gravesen and Lars B. Andersen

Background:

Previous studies have been inconclusive concerning the effect of active transport on BMI. Our objective was to investigate the association between travel mode and BMI in a large community-based sample of Danish adolescents.

Methods:

A cross-sectional survey on health and lifestyle was distributed to all pupils from the 7th to 9th grade (12–16 years of age) in the municipality of Odense, Denmark.

Results:

Cycling to school was associated with 0.38 lower BMI compared to passive travelers (P = .006) after multivariable adjustment. Cycling to school was associated with 0.55 lower odds of being overweight (P < .001) and 0.30 lower (P < .001) odds of being obese compared to individuals using passive transport. Walking to school was associated with 0.65 lower odds of being overweight (P = .006). Post hoc pairwise comparisons of ethnicity revealed that adolescents of foreign ethnicity were more likely to be walkers or passive commuters (75.14% vs. 29.72%) than cyclists (24.86% vs. 70.28%; P < .001) compared to subjects of Danish ethnicity.

Conclusions:

Cycling to school was associated with lower BMI and lower odds of being overweight or obese compared to passive travel in Danish adolescents, whereas walking to school was associated with lower odds of being overweight.

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Anders Grøntved, Grete Skøtt Pedersen, Lars Bo Andersen, Peter Lund Kristensen, Niels Christian Møller and Karsten Froberg

Independent associations between personal- and demographic characteristics and physical activity in 3–6 year old children attending preschool were identified in this study. Boys spent a larger proportion of the time on moderate-and-vigorous physical activity (MVPA; p < .001) and had a higher total physical activity level compared with girls (p < .001). The 3–4 year old children spent less time on MVPA and had a lower total physical activity level compared with both 4–5 (p < .01) and 5–6 year old children (p < .001). The individual preschool, gender and age of preschool children were strong predictors of physical activity (R2-total model=(0.36−0.39)) during preschool attendance.