The effect of structured and lifestyle physical activity interventions on the bone health and body composition of 9-11 year old children

Childhood obesity is becoming increasingly prevalent in the UK and globally. Over the last 10 years, there has been a rise in prevalence of risk factors for health and a decline in physical activity. Obesity is major health risk factor for a number of other chronic diseases, some of which are prevalent in children. Regular physical activity is associated with reduced adiposity, healthier metabolic status lower risk factors of diabetes and CHD and enhanced bone mineral accrual and protection against osteoporosis. Recent literature suggests that children may not be meeting the recommended daily guideline for physical activity of 60 min per day (Riddoch et al., 2007), while others suggest this guideline is insufficient to protect against risk factors in children. Assessment of programmes promoting physical activity, with robust health related outcome measures are therefore warranted Initially, sixty-one children were recruited for a 9-week exploratory trial. The trial assessed the effect of a structured high impact exercise (STEX) and a lifestyle intervention (PASS). Changes in dual-energy X-ray absorptiometry (DXA) derived body composition and bone mineral were compared to age matched controls (CaNT). The STEX intervention resulted in an additional mean increase in total body BMC of 63.3 g (P= 0.019) and an additional increase of 0.011 g.cm-2 (P= 0.018) for BMD over changes observed in controls. Neither intervention stimulated significant increases in BMC or BMD at the femoral neck or lumbar spine (P> 0.05) compared with the controls. No significant changes were found in fat mass index (P> 0.05), lean mass index (P> 0.05) or percent body fat (p = 0.09) in any groups. Structured impact exercise promoted significant and clinically relevant increases in bone measures, without significant changes to body composition. The exploratory finding therefore supported the need for a larger, definitive randomised trial to confirm the results. Following this, a large cohort of Liverpool school children (n=152) was recruited for cross-sectional analysis. Measures included 3-day physical activity using a uniaxial accelerometer, maturity status, cardia-respiratory fitness and skin-fold measurements in addition to body composition, bone mineral content and density. Analysis of variance was used to uncover any sex differences, partial correlation analysis was performed to investigate relationships between health-related variables and physical activity, with maturity offset as the controlling variable. Regression analysis was performed to find the best predictor of BMC and BMD (primary outcome variable), using LM, FM, Mass, and maturity offset as predictor variables. The results showed that children participated in the recommended amount of activity. However, body fat measures indicated that the children fell between the 85th-95% percentile for overweight. Further more BMD status of both sexes also fell below reference values. The dose-response relationship was highlighted as children who participated in 90 min.day" had significantly lower percent body fat (P=0.005) and fat mass (P=0.04) than children who participated in 90 rnin.day") and high-intensity physical activity (over 10 min.day") as a precursor to low body fat and high bone mineral in children. The one hundred and fifty-two children from the baseline cohort were allocated to 1 of 4 groups over a 12 month period. Three groups received a different physical activity intervention; a high-intensity programme ('HIPA'), a skill development programme ('FMS') or a lifestyle-based programme ('PASS'). The 'HIPA' and 'FMS' groups participated in an after-school club (2x60 min.week"), the 'PASS' group attended weekly classroom sessions (1 x week) delivered by a lifestyle coach during the school day. The control group ('CaNT') received health information. All baseline measures were repeated at 9 and 12 months (during and after) intervention. All interventions minimised fat mass accumulation, with the 'HIPA' intervention being most effective (P=0.03), implying that the high-intensity nature of the activity sessions was more effective at minimising body fat accumulation. The greatest magnitude of change in femoral neck BMC (P<0.001) and BMD (P<0.001) and cardiorespiratory fitness (P=0.023) was also reported by the 'HIPA' group which is likely to be attributable to the intensity of the weight-bearing activities included in the 'HIPA' programme. The findings suggested that the 'HIPA' intervention was most beneficial for health outcomes, but all interventions had significant effect on increasing time spent in physical activity. The studies within this thesis have provided a unique insight in to the current bone health status, body composition and physical activity of 9-11 year old Liverpool school children. Further data were also generated on the effect of different physical activity interventions on bone health, body composition and physical activity. The findings from this thesis conclude that a proportion of 9- 11 year old children were overweight despite meeting physical activity recommendations of 60 min.day". The high-intensity physical activity intervention had the most beneficial impact on bone health, body composition and cardio-respiratory fitness when compared to the controls. The quantity of physical activity and the time spent in high intensity activity warrants further investigation to quantify an optimal dose

Physical activity guidelines and cardiovascular risk in children: a cross-sectional analysis to determine whether 60 minutes is enough

Background Physical activity reduces cardiovascular mortality and morbidity. The World Health Organisation (WHO) recommends children engage in 60 min daily moderate-to-vigorous physical activity (MVPA). The effect of compliance with this recommendation on childhood cardiovascular risk has not been empirically tested. To evaluate whether achieving recommendations results in reduced composite-cardiovascular risk score (CCVR) in children, and to examine if vigorous PA (VPA) has independent risk-reduction effects. Methods PA was measured using accelerometry in 182 children (9–11 years). Subjects were grouped according to achievement of 60 min daily MVPA (active) or not (inactive). CCVR was calculated (sum of z-scores: DXA body fat %, blood pressure, VO2peak, flow mediated dilation, left ventricular diastolic function; CVR score ≥1SD indicated ‘higher risk’). The cohort was further split into quintiles for VPA and odds ratios (OR) calculated for each quintile. Results Active children (92 (53 boys)) undertook more MVPA (38 ± 11 min, P  0.05). CCVR in the lowest VPA quintile was significantly greater than the highest quintile (3.9 ± 0.6, P < 0.05), and the OR was 4.7 times higher. Conclusion Achievement of current guidelines has positive effects on body composition and cardiorespiratory fitness, but not CCVR. Vigorous physical activity appears to have beneficial effects on CVD risk, independent of moderate PA, implying a more prescriptive approach may be needed for future VPA guidelines

Relationships between measures of fitness, physical activity, body composition and vascular function in children

Background : The prevalence of obesity and physical inactivity in Western countries has increased rapidly. Both are modifiable risk factors for cardiovascular disease. Atherosclerosis begins in childhood and endothelial dysfunction is its earliest detectable manifestation.Methods : We assessed flow-mediated dilation (FMD) in 129 children (75 female; 10.3 + 0.3 yrs; 54 male; 10.4; 0.3 yrs). FMD was normalised for differences in the eliciting shear rate stimulus between subjects (SRAUC). Fitness was assessed as peak oxygen uptake during an incremental treadmill exercise test (VO2peak). Body composition was measured using a dual-energy X-ray absorptiometry (DEXA) scan. Physical activity (PA) was assessed using Actigraph accelerometers. The cohort was split into tertiles according to FMD% and also FMD% corrected for SRAUC to gain insight into the determinants of vascular function.Results : Across the cohort, significant correlations were observed between FMD%/SRAUC and DEXA percentage fat (r = &minus;0.23, p = 0.009) and percentage lean mass (r = 0.21, p = 0.008), and also with PA performed at moderate-to-high intensity (r = 0.363, p = 0.001). For children in the lowest FMD%/SRAUC tertile, a stronger relationship with all PA measures was observed, particularly with high intensity PA (r = 0.572, P = 0.003). Regression analysis revealed that high intensity PA was the only predictor of impaired FMD%/SRAUC.Conclusions : These data suggest that traditional risk factors for CHD in adult populations impact upon vascular function in young people. Furthermore, it appears that individuals with impaired FMD may benefit from performing high intensity PA, whereas no relationships exist between FMD and lower intensities of PA or between PA and FMD in those subjects who possess preserved vascular function a priori.<br /

Does conduit artery diameter vary according to the anthropometric characteristics of children or men?

Item does not contain fulltextArterial measurements are commonly undertaken to assess acute and chronic adaptations to exercise. Despite the widespread adoption of scaling practices in cardiac research, the relevance of scaling for body size and/or composition has not been addressed for arterial measures. We therefore investigated the relationships between brachial artery diameter and body composition in 129 children aged 9 to 10 yr (75 girls and 54 boys), and 50 men aged 16-49 yr. Body composition variables (total, lean, and fat mass in the whole body, arm, and forearm) were assessed by dual-energy X-ray absorptiometry, and brachial artery diameter was measured using high-resolution ultrasound. Bivariate correlations were performed, and arterial diameter was then scaled using simple ratios (y/x) and allometric approaches after log-log least squares linear regression and production of allometric exponents (b) and construction of power function ratios (y/xb). Size independence was checked via bivariate correlations (x:y/x; x:y/xb). As a result, significant correlations existed between brachial artery diameter and measures of body mass and lean mass in both cohorts (r=0.21-0.48, P0.05). In conclusion, when between- or within-group comparisons are performed under circumstances where it is important to control for differences in body size or composition, allometric scaling of artery diameter should be adopted rather than ratio scaling. Our data also suggest that scaling for lean or total mass may be more appropriate than scaling for indexes of fat mass

Seasonal reduction in physical activity and flow-mediated dilation in children

Purpose: Cardiovascular disease is a process that has its origins in childhood. Endothelial dysfunction is the earliest detectable manifestation of cardiovascular disease. This study aimed to assess the impact of seasonal changes in physical activity (PA) and body composition on conduit artery endothelial function in children. Method: We studied 116 children (70 girls aged 10.7 &plusmn; 0.3 yr and 46 boys aged 10.7 &plusmn; 0.3 yr) on two occasions; in the northern summer (June) and late autumn (November). We assessed flow-mediated dilation (FMD) using high-resolution Doppler ultrasound. Body composition was measured by dual-energy x-ray absorptiometry. PA was assessed using accelerometry. Results: FMD (10.0% &plusmn; 4.3% to 7.9% &plusmn; 3.9%, P &lt; 0.001) and PA (94.1 &plusmn; 34.8 to 77.8 &plusmn; 33.7 min&middot;d-1, P &lt; 0.01) decreased, while percentage body fat increased (27.6% &plusmn; 6.8% to 28.0% &plusmn; 6.6%, P &lt; 0.001) between summer and autumn. Decreases in FMD correlated with decreases in high-intensity PA (r = 0.23, P = 0.04), and change in high-intensity PA was the only predictor of change in FMD. No relationships were evident between changes in body composition and FMD. Conclusions: Vascular function decreased between summer and autumn in this cohort. There were no relationships between change in FMD and changes in body composition or low/moderate-intensity PA. The associations between FMD and high-intensity PA suggests that future interventions should encourage this form of behavior, particularly at the times of year associated with lower PA.<br /