WHAT'S KNOWN ON THIS SUBJECT: Levels of daily physical activity in children are decreasing worldwide. This implies risk factors for cardiovascular and metabolic diseases.WHAT THIS STUDY ADDS: Strength training makes children not only stronger but significantly increases their daily spontaneous physical activity outside the training intervention. abstract BACKGROUND: In developed societies levels of daily physical activity (PA) among school-age children are decreasing. This implies risk factors for cardiovascular and metabolic diseases. Specific strategies to improve levels of PA are needed. In prepubertal boys there is evidence that strength training increases spontaneous PA outside of training. METHODS:A total of 102 schoolchildren (age 10-14 years) in Switzerland were randomly assigned to physical education classes or to participate twice weekly at a guided strength training program for 19 weeks. Spontaneous PA energy expenditure (PAEE; 3axial accelerometry for 7 days), leg and arm strength, and body composition (dual energy radiograph absorptiometry) were measured at baseline, after 19 weeks of training intervention, and after 3 months of washout.RESULTS: There were no significant differences between the groups at baseline. In the intervention group, PAEE increased by 10% from baseline to end of training in boys (P = .02), but not in girls. Leg and arm strength were increased owing to training intervention in both boys and girls. All other variables were unchanged. Baseline PAEE was significantly negatively correlated with changes of PAEE. CONCLUSIONS:Targeted strength training significantly increases daily spontaneous PA behavior in boys. The less active children showed the greatest increase in spontaneous PAEE. Girls showed a similar increase in strength, but not in spontaneous PAEE. This may be explained by their earlier pubertal development. Strength training may be a promising strategy in schools to counteract decreasing levels of PA. Pediatrics 2013;132:1105-1111 AUTHORS: Udo Meinhardt, MD, Fabienne Witassek, MSc, Renato Petrò, BSs, Chris Fritz, BSs, and Urs Eiholzer, MD PEZZ Center for Pediatric Endocrinology Zurich, Zurich, Switzerland KEY WORDS spontaneous physical activity, children, puberty, strength training ABBREVIATIONS BA-bone age FM-fat mass LBM-lean body mass PA-physical activity PAEE-physical activity energy expenditure PE-physical education PWS-Prader-Willi syndrome SDS-standard deviation score Dr Meinhardt conceptualized and designed the study, designed the data collection instruments, carried out the initial data analyses, and revised the manuscript; Ms Witassek conceptualized and designed the study, analyzed output data, and revised the manuscript; Mr Petrò conceptualized and designed the study, coordinated and supervised data collection, and revised the manuscript; Mrs Fritz conceptualized and designed the study, analyzed data, and revised the manuscript; Dr Eiholzer conceptualized and designed the study, analyzed and interpreted data, and revised the manuscript; and all authors approv...

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Background Novel height, weight and body mass index (BMI) references for children in Switzerland reveal an increase in BMI compared to former percentile curves. This trend may be the result of children with parents originating from Southern European countries having a higher risk of being overweight compared to their peers with parents of Swiss origin. We examined the association of generational, migration-related and socioeconomic factors on BMI in Switzerland and expect the results to lead to more targeted prevention programs. Methods From contemporary cross-sectional data, we calculated subgroup-specific BMI percentiles for origin. Results for children of Swiss origin were compared with historical BMI data from Zurich. We tested for the association of overweight and obesity with origin and compared the distributions of BMI percentile ranks. Logistic regression analyses were applied to predict probabilities of being overweight or obese by origin and the Swiss neighborhood index of socioeconomic position (SSEP). Results Compared to the BMI from two generations ago, the newly calculated BMI increased only slightly for children with both parents from Switzerland; 1.2% of these girls and 1.6% of these boys are obese. In the Swiss population, 13% of the children have parents from Southern Europe and the proportion of obesity is 57 and 42% in these boys and girls, respectively. Their BMI medians correspond to those of their parents’ countries of origin. For the probability of being overweight or obese, the SSEP differences are less important than the status of origin. Conclusion We identified children with both parents from Southern Europe as the main influence driving the increase in BMI in Switzerland over the past 50 years. A differentiated consideration of the proportions of various migrant groups within cross-sectional samples is essential when monitoring BMI. Ignoring fluctuations can lead to false conclusions.

Occurrence of breakouts (BO) during casting of narrow slabs is observed to be influenced by the submerged‐entry nozzle (SEN) design in one of ArcelorMittal's thin‐slab casters. To understand the root cause for the BO, three‐dimensional computational fluid dynamics (CFD) models are developed to simulate steady‐state and transient molten steel flow and heat transfer in the SEN and in the CSP caster for three four‐port SEN designs (type‐ A, B, and C), among which exist two major design differences, including the presence of a top insert at SEN tube entrance and height of the flow divider at SEN bottom. CFD models are validated by water model measurements of SEN port opening velocities. Both water model experiments and numerical simulation results suggest that SEN design with a taller bottom flow divider increases both mean and variations of the upper port flow rates and large‐scale asymmetric flows in the CSP mold region. Transient heat transfer simulation results further show that this unstable biased flow in the mold increases “hot spots” near the shell around the funnel‐to‐flat transition region, which could be responsible for local steel re‐melting and potential breakout under certain critical ferrostatic pressure.