Choice of activity-intensity classification thresholds impacts upon accelerometer-assessed physical activity-health relationships in children

It is unknown whether using different published thresholds (PTs) for classifying physical activity (PA) impacts upon activity-health relationships. This study explored whether relationships between PA (sedentary [SED], light PA [LPA], moderate PA [MPA], moderate-to-vigorous PA, vigorous PA [VPA]) and health markers differed in children when classified using three different PTs

A cross-curricular physical activity intervention to combat cardiovascular disease risk factors in 11-14 year olds: 'Activity Knowledge Circuit'

Background: Cardiovascular disease is the leading cause of mortality worldwide. Risk factors associated with cardiovascular disease have been shown to track from childhood through to adulthood. Previous school-based physical activity interventions have demonstrated modest improvements to cardiovascular disease risk factors by implementing extra-curricular activities or improving current physical education curriculum. Few have attempted to increase physical activity in class-room taught curriculum subjects. This study will outline a school-based cross-curricular physical activity intervention to combat cardiovascular disease risk factors in 11-14 year old children. Method/Design: A South Wales Valley school of low socio-economic status has been selected to take part. Participants from year eight (12-13 years) are to be assigned to an intervention group, with maturation-matched participants from years seven (11-12 years) and nine (13-14 years) assigned to a control group. A cross-curricular physical activity intervention will be implemented to increase activity by two hours a week for 18 weeks. Participants will briskly walk 3200 m twice weekly during curriculum lessons (60 minutes duration). With the exception of physical education, all curriculum subjects will participate, with each subject delivering four intervention lessons. The intervention will be performed outdoors and on school premises. An indoor course of equal distance will be used during adverse weather conditions. Cardiovascular disease risk factors will be measured pre- and post-intervention for intervention and control groups. These will take place during physical education lessons and will include measures of stature, mass, waist, hip, and neck circumferences, together with skinfold measure's taken at four sites. Blood pressure will be measured, and fitness status assessed via the 20 m multi-stage fitness test. Questionnaires will be used to determine activity behaviour (physical activity questionnaire for adolescence), diet (seven day food diary) and maturation status. Fasting blood variables will include total cholesterol, lowdensity lipoprotein cholesterol, high density lipoprotein cholesterol, triglycerides, insulin, glucose, high-sensitivity C-reactive protein, interleukin-6, adiponectin, and fibrinogen. Motivational variables and psychological well-being will be assessed by questionnaire. Discussion: Our study may prove to be a cost effective strategy to increase school time physical activity to combat cardiovascular disease risk factors in children.</p

Effect of eating frequency on body composition in 9-11-year-old children

The aim of this study was twofold: a) to examine the association between eating frequency and body composition in children, and b) to identify possible factors that may explain this relationship. Body composition (anthropometry) and dietary intake (3-day food records) were assessed in a cohort of 151 children. After excluding the underreporters (n = 20), data from 131 children (66 boys and 65 girls) aged 9.9 ± 0.1 yr with a BMI of 19.6 ± 0.4 kg/m 2 (means ± se) were used for further analysis. Children were categorized in tertiles based on the daily number of eating episodes. Physical activity was assessed in a subgroup of 48 volunteers with 4-day accelerometry (RT3, Stayhealthy Inc., Monrovia, CA, USA). The number of eating episodes was inversely associated (p &amp;lt; 0.05) with the sum of skinfolds (r = -0.17) and % body fat (r = -0.18) after controlling for age and sex. Frequent eaters presented lower total (p &amp;lt; 0.05) and central adiposity (p &amp;lt; 0.01) compared with the infrequent ones. This was despite the fact that energy intake was higher for the frequent eaters (2077.0 ± 64.3 vs. 1813.0 ± 37.8 kcals/day for the frequent and the infrequent eaters, respectively, p &amp;lt; 0.05). Actually, frequent eaters devoted more time to physical activity than infrequent ones (624.7 ± 13.5 vs. 559.2 ± 23.1 min/day, p &amp;lt; 0.05). In conclusion, high eating frequency was associated with more favorable body composition in this cohort of school children. Increased energy expenditure due to physical activity may, at least in part, explain the favorable body composition of children who eat frequently. © Georg Thieme Verlag KG Stuttgart

Elevated total and central adiposity and low physical activity are associated with insulin resistance in children

The aim of this study was 2-fold: (1) to examine insulin resistance, blood lipid levels, and inflammatory markers in 9- to 11.5-year-old obese and lean children and (2) to identify factors that influence insulin resistance in this cohort of youths. Body mass index, skinfold thickness, waist circumference, physical activity (4-day triaxial accelerometer), cardiorespiratory fitness (submaximal bicycle ergometer test), and dietary intake (3-day food records) were evaluated in 27 obese and 27 lean boys and girls. Fasting blood samples were analyzed for insulin, glucose, lipids and lipoproteins, C-reactive protein (CRP), interleukin 6, soluble intercellular adhesion molecule, and soluble vascular cell adhesion molecule. Homeostasis model assessment (HOMA) was used to evaluate insulin resistance (HOMA-IR). Obese children presented higher HOMA-IR, CRP, and blood lipid levels (all P &lt; .01) compared with lean children. Total body fat and waist circumference were positively associated with fasting insulin (r ≥ 0.51), HOMA-IR (r ≥ 0.56), CRP (r ≥ 0.51), and blood triacylglycerol (r ≥ 0.38), and were inversely correlated with high-density lipoprotein cholesterol (r ≥ -0.39; all P &lt; .01). Cardiorespiratory fitness was inversely associated with HOMA-IR (r = -0.24; P &lt; .05), but this association disappeared when adjusted for age, sex, and fat mass. Waist circumference and total daily physical activity explained 49% of the variance in HOMA-IR in these children. In conclusion, these findings suggest that total and central adiposity are positively associated and physical activity is negatively associated with insulin resistance in children. Interventions to improve glucose metabolism in youth should target at reducing total body and abdominal fat and increasing physical activity. The lack of association between inflammatory markers and HOMA-IR suggests that obesity may precede the elevation of these markers in the evolution of insulin resistance in youth. © 2007 Elsevier Inc. All rights reserved

Effect of rhythmic gymnastics on volumetric bone mineral density and bone geometry in premenarcheal female athletes and controls

Context and Objective: Weight-bearing exercise during growth exerts positive effects on the skeleton. Our objective was to test the hypothesis that long-term elite rhythmic gymnastics exerts positive effects on volumetric bone mineral density and geometry and to determine whether exercise-induced bone adaptation is associated with increased periosteal bone formation or medullary contraction using tibial peripheral quantitative computed tomography and bone turnover markers. Design and Setting: We conducted a cross-sectional study at a tertiary center. Subjects: We studied 26 elite premenarcheal female rhythmic gymnasts (RG) and 23 female controls, aged 9-13 yr. Main Outcome Measures: We measured bone age, volumetric bone mineral density, bone mineral content (BMC), cortical thickness, cortical and trabecular area, and polar stress strength index (SSIp) by peripheral quantitative computed tomography of the left tibia proximal to the distal metaphysis (trabecular) at 14, 38 (cortical), and 66% (muscle mass) from the distal end and bone turnover markers. Results: The two groups were comparable according to height and chronological and bone age. After weight adjustment, cortical BMC, area, and thickness at 38% were significantly higher in RG (P &lt; 0.005-0.001). Periosteal circumference, SSIp, and muscle area were higher in RG (P &lt; 0.01-0.001). Muscle area was significantly associated with cortical BMC, area, and SSIp, whereas years of training showed positive association with cortical BMC, area, and thickness independent of chronological age. Conclusions: RG in premenarcheal girls may induce positive adaptations on the skeleton, especially in cortical bone. Increased duration of exercise is associated with a positive response of bone geometry. Copyright © 2010 by The Endocrine Society