Comparing different accelerometer cut-points for sedentary time in children

Actigraph accelerometers are hypothesized to be valid measurements for assessing children\u27s sedentary time. However, there is considerable variation in accelerometer cut-points used. Therefore, we compared the most common accelerometer sedentary cut-points of children performing sedentary behaviors. Actigraph Actitrainer uniaxial accelerometers were used to measure children\u27s activity intensity (29 children, 5-11 years old) during different activities, namely playing computer games, nonelectronic sedentary games, watching television and playing outdoors. A structured protocol was the criterion for assessing the validity of four common cut-points (100, 300, 800, 1100 counts/minute). The median counts during all sedentary behaviors were below the lowest comparison cut-point of 100 cpm. The 75th percentile values for the sedentary behaviors were always below the cut-point of 300 cpm. Our results suggest that the cut-point of <100 cpm is the most appropriate

Effectiveness of intervention strategies exclusively targeting reductions in children’s sedentary time: a systematic review of the literature

Methodological quality assessment of included studies. (DOCX 57 kb

Determinants of physical activity and exercise in healthy older adults: A systematic review

<p>Abstract</p> <p>Background</p> <p>The health benefits of regular physical activity and exercise have been widely acknowledged. Unfortunately, a decline in physical activity is observed in older adults. Knowledge of the determinants of physical activity (unstructured activity incorporated in daily life) and exercise (structured, planned and repetitive activities) is needed to effectively promote an active lifestyle. Our aim was to systematically review determinants of physical activity and exercise participation among healthy older adults, considering the methodological quality of the included studies.</p> <p>Methods</p> <p>Literature searches were conducted in PubMed/Medline and PsycINFO/OVID for peer reviewed manuscripts published in English from 1990 onwards. We included manuscripts that met the following criteria: 1) population: community dwelling healthy older adults, aged 55 and over; 2) reporting determinants of physical activity or exercise. The outcome measure was qualified as physical activity, exercise, or combination of the two, measured objectively or using self-report. The methodological quality of the selected studies was examined and a best evidence synthesis was applied to assess the association of the determinants with physical activity or exercise.</p> <p>Results</p> <p>Thirty-four manuscripts reporting on 30 studies met the inclusion criteria, of which two were of high methodological quality. Physical activity was reported in four manuscripts, exercise was reported in sixteen and a combination of the two was reported in fourteen manuscripts. Three manuscripts used objective measures, twenty-two manuscripts used self-report measures and nine manuscripts combined a self-report measure with an objective measure. Due to lack of high quality studies and often only one manuscript reporting on a particular determinant, we concluded "insufficient evidence" for most associations between determinants and physical activity or exercise.</p> <p>Conclusions</p> <p>Because physical activity was reported in four manuscripts only, the determinants of physical activity particularly need further study. Recommendations for future research include the use of objective measures of physical activity or exercise as well as valid and reliable measures of determinants.</p

Reliability and validity of the Activity Questionnaire for Adults and Adolescents (AQuAA)

BACKGROUND: Accurate measures of physical activity are highly needed. We evaluated the test-retest reliability and construct validity of the self-report Activity Questionnaire for Adults and Adolescents (AQuAA). The AQuAA is a commonly used questionnaire in Dutch youth. METHODS: In the test-retest reliability study, 53 adolescents and 58 adults completed the AQuAA twice, with an interval of two weeks. In the validity study, 33 adolescents and 47 adults wore an accelerometer (Actigraph) during two weeks, and subsequently completed the AQuAA. RESULTS: In adolescents the test-retest reliability was fair to moderate (intraclass correlations (ICCs) ranging from 0.30 to 0.59). In adults the test-retest reliability was fair to moderate for the time spent on sedentary, light and moderate intensity activities (ICCs ranging from 0.49 to 0.60), but poor for time spent on vigorous activities (ICC = -0.005). The correlations between the AQuAA and Actigraph were low and nonsignificant. Compared with the Actigraph, time spent on all physical activities was significantly higher according to the questionnaire (except for light intensity activities in adolescents), while time spent on sedentary behaviours was significantly lower. CONCLUSION: Reliability of the AQuAA is fair to moderate. The validity of the AQuAA compared to an accelerometer is poor. Both adolescents and adults underestimate the time spent on sedentary behaviours and overestimate the time spent on physical activitie

The neighborhood social environment and body mass index among youth: a mediation analysis

BackgroundThis study aimed to examine associations between aspects of the neighborhood social environment and body mass index (BMI) in youth both cross-sectionally and prospectively; and whether this association was mediated by physical activity, screen-time and sedentary time.MethodsData were collected in 2004 and 2006 in high and low socio-economic areas of Melbourne, Australia. In 2004, 185 children aged 8-9 years (47% boys) and 359 children aged 13-15 years (45% boys) participated. Parents reported their perceptions of aspects of the social environment (i.e. social networks and social trust/cohesion), and physical activity (i.e. time spent outdoors by their children; and their younger children\u27s walking and cycling trips) and screen-time (i.e. TV viewing, computer use). The older children self-reported their walking and cycling trips and their screen-time. All children wore an accelerometer to objectively assess outside-school hours moderate- to-vigorous physical activity and sedentary time. BMI was calculated from height and weight measured in 2004 and 2006. Multilevel linear regression analyses were conducted to examine associations between the social environment and BMI. Mediation analyses using the products of coefficient method were conducted to determine whether associations between the social environment and BMI were mediated by the time spent in a range of physical activity and sedentary behaviors.ResultsCross-sectional and prospective regression analyses showed that a more positive social network and higher social trust/cohesion was related to lower BMI among children. There was no evidence that time spent in physical activity or sedentary behaviors mediated this relation, despite significant associations between social networks and screen-time and between screen-time and BMI.ConclusionsThe findings suggest that the neighborhood social environment may be important for preventing overweight and obesity in children. Further research investigating the mechanisms through which the neighborhood social environment exerts its effect on BMI is needed. <br /

Child-and parent-related correlates of total and prolonged sedentary time in 5-to 6-year-old children

The primary aim was to examine child-and parent-related correlates of accelerometer-assessed overall total and prolonged (i.e., accumulated in bouts of ≥10 consecutive minutes) sedentary time (SED) in 5-to 6-year-old children. Second, child-and parent-related correlates of total and prolonged SED during weekend days and the after school period were examined, as associations with parent-related correlates may be stronger during these periods. SED and moderate-to-vigorous-intensity physical activity (MVPA) were assessed by ActiGraph accelerometers in children (n = 836) and one of their parents/carers. Parents completed a questionnaire examining potential parent-related correlates. Multilevel models examined associations between potential correlates and children’s total and prolonged SED. Children’s MVPA was the only correlate that was consistently negatively associated with both total and prolonged SED across the different time periods (overall, after school, and weekend days). Higher total SED in parents was associated with higher overall total SED and weekend total SED in children. Higher body mass index z-scores of children were associated with lower overall total and prolonged SED. Girls had lower prolonged SED after school than boys. Older children had lower total SED during the weekend. In conclusion, few potential correlates were associated with young children’s total or prolonged SED and most associations differed by time period

Влияние толщины диффузионного слоя на возникновение динамических неустойчивостей в модельном электрокаталитическом процессе

Определено влияние толщины диффузионного слоя Нернста на возникновение неустойчивостей Хопфа, седло–узел и гомоклинной неустойчивости в модельном электрокаталитическом процессе на поверхности сферического электрода при потенциостатических условиях. Показано, что увеличение толщины диффузионного слоя Нернста способстует расширению области потенциалов (в системе могут наблюдаться спонтанные периодические колебания тока), а также области бистабильности системы. Возможная реализация в системе гомоклинной бифуркации может привести и к более сложным динамическим режимам.Визначено вплив товщини дифузійного шару Нернста на виникнення нестійкості Хопфа, сідло–вузол та гомоклінної нестійкості в модельному електрокаталітичному процесі на поверхні сферичного електроду за потенціостатичних умов. Показано, що збільшення товщини дифузійного шару Нернста спричинює розширення області потенціалів (у системі можуть спостерігатися спонтанні періодичні коливання струму), а також області бістабільності системи. Можлива реалізація в системі гомоклінної біфуркації може привести і до більш складних динамічних режимів.The influence of the Nernst diffusion layer thickness on the appearance of the Hopf instability, saddle–node instability, and homoclinic instability in a model electrocatalytic process on a spherical electrode surface under potentiostatic conditions is determined. It is shown that the Nernst diffusion layer thickness increase leads to an increase in the potential range, where spontaneous periodic current oscillations can be observed and also in the system bistability range. A possible realization of the homoclinic bifurcation in the system can initiate more complicated dynamical regimes

Evaluation of the UP4FUN Intervention: A Cluster Randomized Trial to Reduce and Break Up Sitting Time in European 10-12-Year-Old Children

Background: The UP4FUN intervention is a family-involved school-based intervention aiming at reducing and breaking up sitting time at home (with special emphasis on screen time), and breaking up sitting time in school among 10--12 year olds in Europe. The purpose of the present paper was to evaluate its short term effects. Methodology/Principal Findings: A total of 3147 pupils from Belgium, Germany, Greece, Hungary and Norway participated in a school-randomized controlled trial. The intervention included 1–2 school lessons per week for a period of six weeks, along with assignments for the children and their parents. Screen time and breaking up sitting time were registered by self-report and total sedentary time and breaking up sitting time by accelerometry. The effect of the intervention on these behaviors was evaluated by multilevel regression analyses. All analyses were adjusted for baseline values and gender. Significance level was p≤0.01. No significant intervention effects were observed, neither for self-reported TV/DVD or computer/game console time, nor for accelerometer-assessed total sedentary time and number of breaks in sitting time. The intervention group, however, reported more positive attitudes towards (β = 0.25 (95% CI 0.11, 0.38)) and preferences/liking for (β = 0.20 (95% CI 0.08, 0.32)) breaking up sitting time than the control group. Conclusions/Significance: No significant intervention effect on self-reported screen time or accelerometer-assessed sedentary time or breaks in sitting time was observed, but positive effects on beliefs regarding breaking up sitting time were found in favor of the intervention group. Overall, these results do not warrant wider dissemination of the present UP4FUN intervention. Trial Registration: International Standard Randomized Controlled Trial Number Registry ISRCTN3456207

Using Predictive Model for Strategic Control of Multi-reservoir System Storage Capacity

AbstractThe paper will describe the algorithm based on adaptive optimization of multi reservoir control, which the medium-term water flow predictions into the reservoirs for several months ahead repeatedly use. Hydrological prediction model was created using ANN method and values of control outflows are searching by optimization based on evolutionary algorithms optimization technique. The objective function was descripted as the sum of squares deviations between required and actual controlled water outflow from reservoirs where objective function is minimized. The algorithm of adaptive control is applied to the operation storage control of selected reservoir system, which open water reservoirs Vir and Brno are created

Improving Cognitive Performance of 9–12 Years Old Children: Just Dance? A Randomized Controlled Trial

Exercise is assumed to have positive effects on children’s cognitive performance. However, given the inconclusive evidence for the long-term effects of exercise, it is difficult to advice schools on what specific exercise programs can improve children’s cognitive performance. In particular, little is known about the effects of small exercise programs that may be feasible in daily school practice. Therefore, we assessed the effects of a 9-weeks program consisting of daily exercise breaks on children’s cognitive performance, aerobic fitness and physical activity levels. We conducted a cluster-randomized controlled trial in 21 classes of eight Dutch primary schools. A total of 512 children aged 9–12 years participated. The exercise intervention had a duration of 9 weeks and consisted of a daily 10-min classroom-based exercise break of moderate to vigorous intensity. Before and after the intervention, we used four cognitive tasks (i.e., the Attention Network Test, Stroop test, d2 test of attention and Fluency task) to measure children’s cognitive performance in domains of selective attention, inhibition and memory retrieval. In addition, we measured aerobic fitness with a Shuttle Run test and physical activity during school hours by accelerometers. We analyzed data using mixed models, adjusting for baseline scores, class and school. After 9 weeks, there were no intervention effects on children’s cognitive performance or aerobic fitness. Children in the intervention group spent 2.9 min more of their school hours in moderate to vigorous physical activity as compared to the children in the control group. In conclusion, daily 10-min exercise breaks in the classroom did not improve, nor deteriorate cognitive performance in children. The exercise breaks had no effect on children’s fitness, and resulted in 2.9 min more time spent in moderate to vigorous physical activity during school hours. Daily exercise breaks can be implemented in the classroom to promote children’s physical activity during school time, without adverse effect on their cognitive performance