Bianca El-Naaman Hermansen

Objectively measured daily physical activity related to aerobic fitness in young children

Abstract The purpose of this study was to investigate by direct measurement the cross-sectional relationship between accelerometer-measured physical activity and peak oxygen uptake ([Vdot]O2peak: ml · min−1 · kg−1), in a population-based cohort of young children, since such data are scarce. The study included 468 children (246 boys, 222 girls) aged 6.7 ± 0.4 years, recruited from a population-based cohort. Peak oxygen uptake was measured by indirect calorimetry during a maximal treadmill exercise test. Physical activity was assessed by accelerometers over a 4-day period. Minutes of sedentary, light, moderate, moderate-to-vigorous, and vigorous activity per day were calculated. Mean counts per minute were considered to reflect total physical activity. Pearson correlation coefficients indicated a weak relationship between daily physical activity variables and [Vdot]O2peak in boys (r = 0.15–0.28, P < 0.05), with the exception of time in sedentary and light activity, which was not related to [Vdot]O2peak. None of the daily physical activity variables were related to [Vdot]O2peak in girls, with the exception of a very weak relationship for moderate activity (r = 0.14, P < 0.05). Multiple regression analyses indicated that the various physical activity variables explained between 2 and 8% of the variance in [Vdot]O2peak in boys. In this population-based cohort, most daily activity variables were positively related to aerobic fitness in boys, whereas less clear relationships were observed in girls. Our finding that physical activity was only uniformly related to aerobic fitness in boys partly contradicts previous studies in older children and adolescents.

Cytokines and clustered cardiovascular risk factors in children

The aim was to evaluate the possible role of tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), C-reactive protein (CRP), low fitness, and fatness in the early development of clustering of cardiovascular disease (CVD) risk factors and insulin resistance. Subjects for this cross-sectional study were obtained from 18 schools near Copenhagen, Denmark. Two hundred ten 9-year-old children were selected for cytokine analysis from 434 third-grade children with complete CVD risk profiles. The subgroup was selected according to the CVD risk factor profile (upper and lower quartile of a composite CVD risk score). All the CVD risk factors and CRP differed between the high- and low-risk groups; but plasma glucose, TNF-alpha, and IL-6 had small and inconsistent differences. Strong associations were found between CVD risk scores and fitness (VO(2peak)) or fatness. No associations were found between CVD risk scores and TNF-alpha and IL-6. C-reactive protein was associated with fitness, fatness, and CVD risk score. This study does not support an association between plasma IL-6 or TNF-alpha and low insulin sensitivity or clustering of CVD risk factors in a young cohort. Inflammation was more pronounced in fat and unfit children based on the association with CRP levels. The association between fitness and fatness variables, insulin resistance, and clustered risk could be caused by other mechanisms related to these exposures. The role of IL-6 remains unclear.

Daily physical activity and sports participation among children from ethnic minorities in Denmark

Abstract The purpose of this study was to investigate whether Danish children from immigrant backgrounds are less physically active than children from the ethnic majority, and to investigate the possible reasons for any differences found. Accelerometer measures of physical activity as well as questionnaire data about organised sports, family demography, resources and values were collected from 594 children of whom 67 had other ethnic background than Danish. Data were collected when the children were 6–7 years old and again later when the children were 9–10 years old. It was found that children from immigrant backgrounds were not less physically active than other children when their amounts of daily physical activity were measured by direct objective measures, despite their participation rate in organised sports being much lower. Using multiple logistic regression modelling, this study showed that lack of parental experience with organised sports and lack of economic/material resources explained much of the difference in sports participation. Children of immigrant background had significant lower participation in club sports but this did not affect their overall physical activity level.

Aerobic fitness in prepubertal children according to level of body fat

Aim:  The purpose of this study was to investigate the relationship between maximum oxygen uptake (VO2PEAK) and body fat in young children on a population‐based level.