Search

Background: In today's society, few adolescents meet physical activity guidelines and effects of physical activity promoting programmes are disappointing. In studies exploring determinants of physical activity, the perspective of adolescents themselves is largely lacking. Also, there is a lack of knowledge on potential environmental determinants of adolescent physical activity. Therefore, this study aimed to explore adolescents' perspectives on characteristics of an activity-friendly environment., Methods: Concept mapping meetings were conducted with four secondary school classes, including 115 adolescents (13-17 years). Each student generated ideas regarding the characteristics of an activity-friendly environment. For each school class, ideas were combined and identical ideas were removed. Next, students individually sorted all ideas, based on self-perceived similarity, and rated their importance on a five-point Likert-scale. A concept map was created for each school class using multidimensional scaling and hierarchical cluster analysis. Finally, the researchers named the potential environmental determinants within the clusters., Results: The concept maps depicted 23 unique potential determinants of activity friendliness, of which 15 were similar across all school classes. Potential determinants were categorized in the physical-, social-, economic-, and motivational domain. The most frequent and important adolescent-perceived determinants of activity friendliness across all school classes belonged to the physical domain, e.g. a suitable area including a proper surface for a variety of sports, and good lighting in the playground., Conclusions: Our findings show that adolescents perceive potential determinants in the physical and economic domain as most important for activity friendliness, indicating that future interventions might benefit from targeting potential determinants within these domains.

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.

Evidence of adverse health effects of TV viewing is stronger than for overall sedentary behaviour in youth. One explanation may be that TV viewing involves less body movement than other sedentary activities. Variations in body movement across sedentary activities are currently unknown, as are age differences in such variations. This study examined body movement differences across various sedentary activities in children and adolescents, assessed by hip-, thigh- and wrist-worn accelerometers, muscle activity and heart rate. Body movement differences between sedentary activities and standing were also examined. Fifty-three children (aged 10⁻12 years) and 37 adolescents (aged 16⁻18 years) performed seven different sedentary activities, a standing activity, and a dancing activity (as a control activity) in a controlled setting. Each activity lasted 10 minutes. Participants wore an Actigraph on their hip and both wrists, an activPAL on their thigh and a heart rate monitor. The muscle activity of weight-bearing leg muscles was measured in a subgroup ( n = 38) by surface electromyography. Variations in body movement across activities were examined using general estimation equations analysis. Children showed significantly more body movement during sedentary activities and standing than adolescents. In both age groups, screen-based sedentary activities involved less body movement than non-screen-based sedentary activities. This may explain the stronger evidence for detrimental health effects of TV viewing while evidence for child sedentary behaviour in general is inconsistent. Differences in body movement during standing and sedentary activities were relatively small. Future research should examine the potential health effects of differences in body movement between screen-based versus non-screen based and standing versus sedentary activities.

Objective: Certain exercise prescriptions for patients with cancer may improve self-reported quality of life (QoL) and self-reported physical function (PF). We investigated the effects of exercise on QoL and PF in patients with cancer and studied differences in effects between different intervention-related and exercise-related characteristics., Design: We searched four electronic databases to identify randomised controlled trials investigating exercise effects on QoL and PF in patients with cancer. Pooled effects (Hedges' g) were calculated using Comprehensive Meta-Analysis software. Subgroup analyses were conducted based on intervention dimensions, including timing, duration and delivery mode, and exercise dimensions, including frequency, intensity, type and time (FITT factors)., Results: We included 74 exercise arms. Patients who were randomised to exercise interventions had significantly improved QoL (g=0.15, 95% CI (0.10 to 0.20), n=67 exercise arms) and PF (g=0.21, 95% CI (0.15 to 0.27), n=59 exercise arms) compared with patients in control groups. We found a significant between-group difference for exercise delivery mode, with significant beneficial effects for supervised exercise interventions (g=0.20, 95% CI (0.14 to 0.26) for QoL and g=0.27, 95% CI (0.20 to 0.33) for PF), but not for unsupervised interventions (g=0.04, 95% CI (-0.06 to 0.13) for QoL and g=0.09, 95% CI (-0.01 to 0.19) for PF). No statistically significant differences in intervention effects were found for variations in intervention timing, duration or exercise FITT factors. Unsupervised exercise with higher weekly energy expenditure was more effective than unsupervised exercise with lower energy expenditure (z=2.34, p=0.02)., Conclusions: Exercise interventions, especially when supervised, have statistically significant and small clinical benefit on self-reported QoL and PF in patients with cancer. Unsupervised exercise intervention effects on PF were larger when prescribed at a higher weekly energy expenditure., Competing Interests: Competing interests: None declared., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Children from disadvantaged areas are hard to reach for interventions aimed at promoting healthy lifestyles. We conducted a participatory needs assessment, in which researchers collaborated with a community in a disadvantaged area in Amsterdam to gain an understanding of the health-related issues of children within this community. Qualitative data was collected through: three to four participatory group meetings with three groups of 9-12-year-old children ( n = 5-9 per group); nine interviews with professionals working with youth; two interviews with parents and their children; and informal meetings including 31 parents. All transcriptions or summaries were coded and analyzed. Childhood overweight/obesity was indicated as the main health issue. A lack of physical activity and unhealthy dietary behavior were identified as the main risk factors, with underlying determinants such as culture, habits, finances, and social norms. Identified needs included more supervised, low-priced sports activities at a nearby location and more education on adopting a healthy diet. Our participatory health needs assessment resulted in a comprehensive overview of the most relevant risk factors and determinants of childhood overweight/obesity and needs from the community's perspective. This knowledge aids in the development of better tailored, and thereby potentially more effective, interventions., Competing Interests: The authors declare no conflict of interest.

Background: As physical inactivity is particularly prevalent amongst lower-educated adolescent girls, interventions are needed. Using a co-creational approach increases their engagement and might be effective. This study aimed to: (1) describe the co-creation process, (2) evaluate how girls experienced co-creation, and (3) evaluate the effect of the co-creational interventions on physical activity, individual, sociocultural and school-based factors. Methods: Three intervention schools (n = 91) and three control schools (n = 105) across Flanders participated. A questionnaire was completed pre (September-October 2014) and post (April-May 2015). In between, sessions with a co-creation group were organised to develop and implement the intervention in each intervention school. Focus groups were conducted to evaluate the co-creational process. Results: School 1 organised sport sessions for girls, school 2 organised a fitness activity and set up a Facebook page, school 3 organised a lunch walk. Girls were positive about having a voice in developing an intervention. No significant effects were found, except for small effects on extracurricular sports participation and self-efficacy. Conclusions: Using a co-creational approach amongst adolescent girls might be a feasible approach. However, as interventions were minimal, effects were limited or undetectable. Future co-creation projects could consider the most optimal co-creation process, evaluation design and intensively test this approach., Competing Interests: The authors declare no conflict of interest.

Todays children spend a large amount of their time sedentary. There is limited evidence on the determinants of sedentary behavior in children, and qualitative studies are especially lacking. Therefore, this study aimed to explore determinants of children's sedentary behavior from the child- and parent perspective. Qualitative data were collected during concept mapping sessions with four groups of 11-13 years old children ( n = 38) and two online sessions with parents ( n = 21). Children and parents generated sedentary behavior motives, sorted related motives, and rated their importance in influencing children's sedentary time. Next, multidimensional scaling and hierarchical cluster analysis was performed to create clusters of motives resulting in a concept map. Finally, the researchers named the clusters in the concept map. Concept maps of children yielded eight to ten perceived determinants, and concept maps of parents six to seven. Children and parents identified six similar potential determinants, and both rated as important: Sitting because… "it is the norm (I have to)", and "I can work/play better that way". In addition, children rated "there is nobody to play with" as an important potential determinant for engaging in sedentary behavior. The most important child- and parent perceived determinants were related to the social/cultural and physical environment, indicating that these are promising targets for future interventions., Competing Interests: The authors declare no conflict of interest.

Background: This study examined the frequency of and differences in sedentary bouts of different durations and the total time spent in sedentary bouts on a weekday, a weekend day, during school hours, during after-school hours and in the evening period in a sample of 10- to 12-year-old Belgian children., Methods: Accelerometer data were collected as part of the ENERGY-project in Belgium (n = 577, 10.9 ± 0.7 years, 53% girls) in 2011. Differences in total sedentary time, sedentary bouts of 2-5, 5-10, 10-20, 20-30 and ≥30 min and total time accumulated in those bouts were examined on a weekday, a weekend day, during school hours, during after-school hours and in the evening period, using multilevel analyses in MLwiN 2.22., Results: More than 60% of the participants' waking time was spent sedentary. Children typically engaged in short sedentary bouts of 2-5 and 5-10 min, which contributed almost 50% towards their total daily sedentary time. Although the differences were very small, children engaged in significantly fewer sedentary bouts of nearly all durations during after-school hours compared to during school hours and in the evening period. Children also engaged in significantly fewer sedentary bouts of 5-10, 10-20, and 20-30 min per hour on a weekend day than on a weekday., Conclusions: Although primary school children spend more than 60% of their waking time sedentary, they generally engaged in short sedentary bouts. Children's sedentary bouts were slightly longer on weekdays, particularly during school hours and in the evening period, although the differences were very small. These results suggest that in this age group, interventions focusing on reducing total sedentary time rather than interrupting prolonged sedentary time are needed.

Background: The prominence of sedentary behavior research in health science has grown rapidly. With this growth there is increasing urgency for clear, common and accepted terminology and definitions. Such standardization is difficult to achieve, especially across multi-disciplinary researchers, practitioners, and industries. The Sedentary Behavior Research Network (SBRN) undertook a Terminology Consensus Project to address this need., Method: First, a literature review was completed to identify key terms in sedentary behavior research. These key terms were then reviewed and modified by a Steering Committee formed by SBRN. Next, SBRN members were invited to contribute to this project and interested participants reviewed and provided feedback on the proposed list of terms and draft definitions through an online survey. Finally, a conceptual model and consensus definitions (including caveats and examples for all age groups and functional abilities) were finalized based on the feedback received from the 87 SBRN member participants who responded to the original invitation and survey., Results: Consensus definitions for the terms physical inactivity, stationary behavior, sedentary behavior, standing, screen time, non-screen-based sedentary time, sitting, reclining, lying, sedentary behavior pattern, as well as how the terms bouts, breaks, and interruptions should be used in this context are provided., Conclusion: It is hoped that the definitions resulting from this comprehensive, transparent, and broad-based participatory process will result in standardized terminology that is widely supported and adopted, thereby advancing future research, interventions, policies, and practices related to sedentary behaviors.

This review aimed to summarize the evidence on the effectiveness of obesity prevention and treatment programmes for adolescents from socioeconomically disadvantaged backgrounds. A secondary aim was to identify potential successful intervention strategies for this target group. PubMed, EMBASE, PsycINFO and Cochrane Library were searched from January 2000 up to February 2016. Intervention studies targeting adolescents from disadvantaged backgrounds were included, with body mass index as outcome. Secondary outcomes were other adiposity measures, physical activity, diet, sedentary behaviour and screen time. Two independent reviewers extracted data, coded intervention strategies and conducted quality assessments. Fourteen studies were included: nine obesity prevention and five obesity treatment studies. Two preventive and four treatment studies showed significant beneficial effects on body mass index. Five of six studies (four preventive, one treatment studies) measuring dietary behaviour reported significant intervention effects. Evidence on other secondary outcomes was inconclusive. We found no conclusive evidence for which specific intervention strategies were particularly successful in preventing or treating obesity among disadvantaged adolescents. However, the current evidence suggests that involving adolescents in the development and delivering of interventions, the use of experiential activities and involvement of parents seem to be promising strategies. More high quality studies are needed. PROSPERO registration number: CRD42016041612., (© 2017 The Authors. Obesity Reviews published by John Wiley & Sons Ltd on behalf of World Obesity.)

Background: Both parents' and children's perception of children's weight status may be important predictors of slimming and energy-balance related behaviours, independent of children's actual weight status., Objectives: We examined the cross-sectional association of children's self-reported slimming and energy-balance related behaviours with children's (i) actual, (ii) self-perceived and (iii) parent-perceived weight status., Methods: Data of 10- to 12-year-old European children and their parents were used. Multilevel logistic and linear regression analyses were performed, adjusting for age, gender, parental weight controlling behaviours, education, marital status and ethnicity., Results: Independent of their actual weight status, a higher proportion of children reported slimming when they or their parents perceived them as too fat. Children's self-perceived weight status was more strongly associated with slimming than their parents' perception or their actual weight status. Moreover, children who perceive themselves as overweight reported less physical activity and more screen time. Children whose parents perceive them as overweight reported less physical activity., Conclusions: Children's own perception of their weight status appears to be more important for their self-reported slimming than their actual or their parent's perceptions of their weight status. Additionally, children's self-perceived weight status seems important in engaging more physical activity and reduces screen time., (© 2016 World Obesity Federation.)

Background: Accurate measurement of child sedentary behavior is necessary for monitoring trends, examining health effects, and evaluating the effectiveness of interventions., Objectives: We therefore aimed to summarize studies examining the measurement properties of self-report or proxy-report sedentary behavior questionnaires for children and adolescents under the age of 18 years. Additionally, we provided an overview of the characteristics of the evaluated questionnaires., Methods: We performed systematic literature searches in the EMBASE, PubMed, and SPORTDiscus electronic databases. Studies had to report on at least one measurement property of a questionnaire assessing sedentary behavior. Questionnaire data were extracted using a standardized checklist, i.e. the Quality Assessment of Physical Activity Questionnaire (QAPAQ) checklist, and the methodological quality of the included studies was rated using a standardized tool, i.e. the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist., Results: Forty-six studies on 46 questionnaires met our inclusion criteria, of which 33 examined test-retest reliability, nine examined measurement error, two examined internal consistency, 22 examined construct validity, eight examined content validity, and two examined structural validity. The majority of the included studies were of fair or poor methodological quality. Of the studies with at least a fair methodological quality, six scored positive on test-retest reliability, and two scored positive on construct validity., Conclusion: None of the questionnaires included in this review were considered as both valid and reliable. High-quality studies on the most promising questionnaires are required, with more attention to the content validity of the questionnaires. PROSPERO registration number: CRD42016035963.

Background: Healthy sleep among children has social, physical and mental health benefits. As most of today’s children do not meet the healthy sleep recommendations, effective interventions are urgently needed. This systematic review summarizes the characteristics and effectiveness of interventions aiming to stimulate healthy sleeping in a general population of school-aged children., Methods: The search engines PubMed, Embase, Web of Science, PsycInfo and the Cochrane Database Library were systematically searched up to March 2016. We included all studies evaluating interventions targeting healthy sleep duration and/or bedtime routines of children aged 4–12 years. All steps in this systematic review, i.e. search, study selection, quality assessment and data extraction, were performed following CRD Guidelines and reported according to the PRISMA Statement., Results: Eleven studies were included, of which only two were of strong quality. The interventions varied in terms of targeted determinants and intervention setting. Overall, no evidence was found favoring a particular intervention strategy. One intervention that delayed school start time and two multi-behavioral interventions that targeted both the school and home setting showed promising effects in terms of increasing sleep duration., Conclusion: Due to few high quality studies, evidence for the effectiveness of any particular intervention strategy to stimulate healthy sleep in children is still inconclusive. However, the more effective interventions in stimulating healthy sleep duration and adherence to regular bedtimes were mostly multi-behavioral interventions that included creating daily healthy routines and combined intervention settings (e.g. home and school). In conclusion, high-quality studies evaluating systematically developed interventions are needed to move this field forward., (© The Author 2017. Published by Oxford University Press on behalf of the European Public Health Association. All rights reserved.)

Background: Recent experimental studies in adults have demonstrated that interruptions to prolonged sitting have beneficial effects on metabolic risk factors in adults, compared to prolonged sitting. We explored the hypothesis that multiple consecutive days of predominantly prolonged sedentary time may have an unfavorable effect on the postprandial response of C-peptide, glucose, and triglycerides in free-living healthy young men. Methods: In this explorative pilot study, healthy young men ( n = 7; 18-23 years) consumed standardized mixed meals at 1 and 5 h during two experimental laboratory-sitting days, with 6 days of predominantly prolonged sedentary time in between. Serum and plasma samples were obtained hourly from 0 to 8 h for measurement of glucose, C-peptide, and triglycerides. Participant's sedentary time was monitored using an accelerometer during the prolonged sedentary days as well as during 6 normal days prior to the first laboratory day. Differences in postprandial levels were assessed using generalized estimating equations analysis. Due to the explorative nature of this study and the small sample size, p -value was set at <0.10. Results: Overall, when expressed as % of wear time, sedentary time was 5% higher during the 6 prolonged sedentary days, which was not significantly different compared to the 6 normal days ( n = 4). Following 6 prolonged sedentary days, postprandial levels of C-peptide were significantly higher than at baseline (B = 0.11; 90%CI = [0.002; 0.22]; n = 7). Postprandial levels of glucose and triglycerides were not significantly different between the 2 laboratory days. Conclusions: Due to the relatively high sedentary time at baseline, participants were unable to increase their sedentary time substantially. Nevertheless, postprandial C-peptide levels were slightly higher after 6 prolonged sedentary days than after 6 normal days.

Objectives: Evidence suggests that physical activity is positively related to several aspects of cognitive functioning in children, among which is selective attention. To date, no information is available on the optimal frequency of physical activity on cognitive functioning in children. The current study examined the acute effects of one and two bouts of moderate-intensity physical activity on children's selective attention., Design: Randomized controlled trial (ISRCTN97975679)., Methods: Thirty boys and twenty-six girls, aged 10-13 years, were randomly assigned to three conditions: (A) sitting all morning working on simulated school tasks; (B) one 20-min physical activity bout after 90min; and (C) two 20-min physical activity bouts, i.e. at the start and after 90min. Selective attention was assessed at five time points during the morning (i.e. at baseline and after 20, 110, 130 and 220min), using the 'Sky Search' subtest of the 'Test of Selective Attention in Children'. We used GEE analysis to examine differences in Sky Search scores between the three experimental conditions, adjusting for school, baseline scores, self-reported screen time and time spent in sports., Results: Children who performed two 20-min bouts of moderate-intensity physical activity had significantly better Sky Search scores compared to children who performed one physical activity bout or remained seated the whole morning (B=-0.26; 95% CI=[-0.52; -0.00])., Conclusions: Our findings support the importance of repeated physical activity during the school day for beneficial effects on selective attention in children., (Copyright © 2015 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)

Evidence for adverse health effects of excessive sedentary behaviour in children is predominantly based on cross-sectional studies, measuring TV viewing as proxy for sedentary behaviour. This systematic review and meta-analysis summarizes the evidence on the prospective relationship between childhood sedentary behaviour and biomedical health indicators, overall and stratified by type of sedentary behaviour (TV viewing, computer use/games, screen time and objective sedentary time). PubMed, EMBASE, PsycINFO and Cochrane were systematically searched till January 2015. Methodological quality of all included studies was scored, and a best evidence synthesis was applied. We included 109 studies of which 19 were of high quality. We found moderate-to-strong evidence for a relationship of overall sedentary time with some anthropometrics (overweight/obesity, weight-for-height), one cardiometabolic biomarker (HDL-cholesterol) and some fitness indicators (fitness, being unfit). For other health indicators, we found no convincing evidence because of inconsistent or non-significant findings. The evidence varied by type of sedentary behaviour. The meta-analysis indicated that each additional baseline hour of TV viewing (β = 0.01, 95%CI = [-0.002; 0.02]) or computer use (β = 0.00, 95%CI = [-0.004; 0.01]) per day was not significantly related with BMI at follow-up. We conclude that the evidence for a prospective relationship between childhood sedentary behaviour and biomedical health is in general unconvincing., (© 2016 The Authors. Obesity Reviews published by John Wiley & Sons Ltd on behalf of International Association for the Study of Obesity (IASO).)

An increasing number of interventions targeting sedentary behaviour in children have emerged in recent years. Recently published reviews included sedentary behaviour and physical activity interventions. This review critically summarizes evidence on the effectiveness of intervention strategies that exclusively targeted reducing sedentary time in children and adolescents. We performed a systematic literature search in Pubmed, Embase and the Cochrane Library through November 2015. Two independent reviewers selected eligible studies, extracted relevant data and rated the methodological quality using the assessment tool for quantitative studies. We included 21 intervention studies, of which 8 studies scored moderate on methodological quality and 13 studies scored weak. Four out of eight moderate quality studies reported significant beneficial intervention effects.Although descriptions of intervention strategies were not always clearly reported, we identified encouragement of a TV turnoff week and implementing standing desks in classrooms as promising strategies. Due to a lack of high quality studies and inconsistent findings, we found no convincing evidence for the effectiveness of existing interventions targeting solely sedentary behaviour. We recommend that future studies apply mediation analyses to explore which strategies are most effective. Furthermore, to increase the effectiveness of interventions, knowledge of children's motives to engage in sedentary behavior is required, as well as their opinion on potentially effective intervention strategies.

School playgrounds are important physical activity (PA) environments for children, yet only a small number of children reaches the target of 40% of moderate-to-vigorous PA time during recess. The aim of this study was to explore children's perspectives (i.e., child-identified determinants) of activity-friendly school playgrounds. We conducted participatory research with children as co-researchers, framed as a project to give children the opportunity to discuss their views and ideas about their school playgrounds. At three schools, six children (9-12 years old) met over five to seven group meetings. Data analysis included children's conclusions obtained during the project and the researcher's analysis of written reports of all meetings. Children indicated a strong desire for fun and active play, with physical playground characteristics and safety, rules and supervision, peer-interactions, and variation in equipment/games as important determinants. Our results indicate that improving activity-friendliness of playgrounds requires an integrated and multi-faceted approach. It also indicates that children, as primary users, are able to identify barriers for active play that are easily overlooked, unknown or differently perceived by adults. Hence, we believe that structural involvement of children in designing, developing and improving playgrounds may increase children's' active play and consequently PA levels during recess.

Existing research evidence indicates that children and adolescents of parents with a low socioeconomic position spend more time on sedentary behaviour than their counterparts. However, the mechanisms driving these differences remain poorly understood. The main aim of this systematic review was to summarize the evidence regarding the association between socioeconomic position and correlates of sedentary behaviour among youth (0-18 years) from developed countries. The literature search was conducted using MEDLINE, Embase, CINAHL and PsycINFO. A total of 37 studies were included. All but three studies examined screen-based sedentary behaviours only. Methodological quality ranged from low to moderate. Education was the most commonly used indicator of socioeconomic position, followed by income. Socioeconomic position was inversely related to the presence of a TV in the child's bedroom, parental modelling for TV viewing, parental co-viewing and eating meals in front of the TV. We found no/indeterminate evidence for an association between socioeconomic position and rules and regulations about screen time. The findings suggest possible factors that could be targeted in future intervention studies to decrease screen-based sedentary behaviour in lower socioeconomic groups in particular., (© 2015 World Obesity.)

Background and Objective: Several early life determinants play a role in childhood obesity. Rapid weight gain and overweight in infancy increases the risk while breast feeding seems to protect against childhood overweight. However, should we worry about exclusively breastfed overweight infants? The aim of the study is to examine the association of feeding type (exclusive breast feeding (EBF), formula feeding or mixed feeding) and overweight at the age of 6 months with the risk of overweight at the age of 5-6 years., Methods: The Amsterdam Born Children and their Development study is a large prospective population-based birth cohort study conducted in Amsterdam, the Netherlands. Children with complete information pertaining to feeding type and weight status at the age of 6 months and 5-6 years were included (N=3367). EBF was defined as receiving only breast feeding for at least 3 months. Overweight at the ages of 6 months and 5-6 years were defined by the WHO child growth standards and the International Obesity Task Force guidelines, respectively. The association of feeding type and overweight at 6 months with overweight at 5-6 years was assessed using logistic regression analyses., Results: Overweight infants have a 4.10-fold (95% CI 2.91 to 5.78) higher odds of childhood overweight compared with those who were not overweight, independent of feeding type. EBF did not affect the association between infant overweight and childhood overweight., Conclusions: Overweight in infancy increases the odds of childhood overweight, equally for exclusively breastfed and formula fed infants. Overweight prevention should start before or at birth and applies to formula fed children as well as exclusively breastfed children., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Increasing attention is paid to the potential health effects of children's sedentary bouts and breaks, rather than total sedentary time. This paper discusses currently used operational definitions of sedentary bouts and breaks in studies among children. Remarkably, these studies applied different operational definitions, complicating comparison between studies. To advance the field of sedentary behaviour epidemiology, we need a clear and 'evidence-based' operationalization for such sedentary bouts and breaks., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Objective: This study examined the occurrence and duration of sedentary bouts and explored the cross-sectional association with health indicators in children applying various operational definitions of sedentary bouts., Methods: Accelerometer data of 647 children (10-13 years old) were collected in five European countries. We analyzed sedentary time (<100 cpm) accumulated in bouts of at least 5, 10, 20 or 30 min based on four operational definitions, allowing 0, 30 or 60s ≥100 cpm within bouts. Health indicators included anthropometrics (i.e. waist circumference and body mass index (BMI)) and in a subsample from two European countries (n=112) fasting capillary blood levels of glucose, C-peptide, high-density- and low-density cholesterol, and triglycerides. Data collection took place from March to July 2010. Associations were adjusted for age, gender, moderate-to-vigorous physical activity, total wear time and country., Results: Occurrence of sedentary bouts varied largely between the various definitions. Children spent most of their sedentary time in bouts of ≥5 min while bouts of ≥20 min were rare. Linear regression analysis revealed few significant associations of sedentary time accumulated in bouts of ≥5-30 min with health indicators. Moreover, we found that more associations became significant when allowing no tolerance time within sedentary bouts., Conclusion: Despite a few significant associations, we found no convincing evidence for an association between sedentary time accumulated in bouts and health indicators in 10-13 year old children., (Copyright © 2015. Published by Elsevier Inc.)

Aim: This study aims to establish evidence-based accelerometer data reduction criteria to accurately assess total sedentary time and sedentary patterns in children., Methods: Participants (n = 1057 European children; 9-13 yrs) were invited to wear an accelerometer for at least 6 consecutive days. We explored 1) non-wear time criteria; 2) minimum daily valid wear time; 3) differences between weekday and weekend day; and 4) minimum number of days of accelerometer wear by comparing the effects of commonly used data reduction decisions on total sedentary time, and duration and number of prolonged sedentary bouts., Results: More than 60 consecutive minutes of zero counts was the optimal criterion for non-wear time. Increasing the definition of a valid day from 8 to 10 hours wear time hardly influenced the sedentary outcomes, while the sample size of children with more than 4 valid days increased from 69 to 81%. On weekdays, children had on average 1 hour more wear time, 50 minutes more total sedentary time, 26 minutes more sedentary time accumulated in bouts, and 1 more sedentary bout. At least 6 days of accelerometer data were needed to accurately represent weekly sedentary time and patterns., Conclusions: Based on our results we recommend 1) a minimum of 60 minutes of consecutive zeros as the most realistic criterion for non-wear time; and 2) including at least six days with minimum eight valid hours to characterize children's usual total sedentary time and patterns, preferably including one weekend day.

Background: Evidence on the association between different screen behaviours and cardiometabolic biomarkers in children is limited. We examined the independent relationship of TV time and PC time with cardiometabolic biomarkers in Dutch 5-6 year old children., Methods: Cross-sectional analyses were conducted December 2012-March 2013 using data from a multi-ethnic cohort (the ABCD study, n = 1,961). TV and PC time and physical activity were assessed by parent-report. Body weight, height, waist circumference and blood pressure were measured using a standard protocol. Fasting capillary blood samples were collected. A cardiometabolic function score was computed as the mean of the inverted standardised values of waist circumference, mean of systolic and diastolic blood pressure, glucose, HDLC (not inverted), and triglycerides., Results: Mean TV time was 1.2 (± 0.8) hr/day and mean PC time was 0.2 (± 0.4) hr/day. After adjustment for birth weight, height, maternal education, PC time, and physical activity, excessive TV time (>2 hrs/day) was adversely associated with waist circumference (b = 0.39, 95% CI: 0.004;0.78) while PC time was beneficially associated with HDLC levels (b = 0.04, 95% CI: 0.001;0.08). We found no additional significant associations of TV time, or PC time with any of the cardiometabolic biomarkers., Conclusions: We found no convincing evidence for an association between TV or PC time and cardiometabolic function in apparently healthy 5-6 yr olds.

Background: Sedentary time has been identified as an important and independent risk factor for the development of type 2 diabetes mellitus (T2DM) and cardiovascular diseases (CVD) in adults. However, to date most studies have focused on TV time, few also included other sedentary behaviours such as computer use and reading, and most studies had a cross-sectional design. We aimed to examine the prospective relationship between time spent on sedentary behaviours in different domains with individual and clustered cardiometabolic risk in adults., Methods: Longitudinal data of 622 adults aged 30-50 years (42% males) at increased cardiometabolic risk were used. Leisure time TV viewing, computer use, reading and other sedentary activities (e.g. passive transport) were assessed using a subscale of the Activity Questionnaire for Adolescents and Adults (AQuAA), and summed into overall sedentary behaviour (min/day). Weight and blood pressure were measured, waist-to-hip ratio and BMI calculated, and fasting plasma levels of glucose, HbA1c, total cholesterol, HDL-cholesterol, LDL-cholesterol and triglycerides determined. T2DM risk score was estimated according to the ARIC formula and CVD mortality risk according to the SCORE formula., Results: Generalized Estimating Equation analysis demonstrated that over a two-year period higher levels of overall sedentary time and TV time were weakly but negatively associated with one out of 13 studied cardiometabolic risk factors (i.e. HDL cholesterol)., Conclusion: Overall sedentary time, as well as sedentary time in different domains, was virtually not related with cardiometabolic risk factors.

Background: The aim of the study was to examine the association of daily variations in rainfall and temperature with sedentary time (ST) and physical activity (PA) in European children., Methods: Children were included from 5 countries (Belgium, Greece, Hungary, the Netherlands, Switzerland) as part of the ENERGY-project. We used cross-sectional data from 722 children aged 10-12 years (47% boys). ST and PA were measured by accelerometers for 6 consecutive days, including weekend days. Weather data were collected from online national weather reports. Multilevel regression models were used for data analyses., Results: Maximum temperature was positively associated with light PA (β = 3.1 min/day; 95% CI = 2.4-3.8), moderate-to-vigorous PA (β = 0.6 min/day; 95% CI = 0.4-0.8), and average PA [β = 4.1 counts per minute (cpm); 95% CI = 1.6-6.5, quadratic relationship]. Rainfall was inversely and quadratically associated with light PA (β = -1.3 min/day; 95% CI = -1.9 to -0.6), moderate-to-vigorous PA (β = -0.6 min/day; 95% CI = -0.8 to -0.3), and average PA (β = -1.6 cpm; 95% CI = -2.2 to -0.9). Maximum temperature was not significantly associated with ST (β = -0.2 min/day; 95% CI = -1.0 to 0.6), while rainfall was positively associated with ST (β = 0.9 min/day; 95% CI = 0.6-1.3)., Conclusion: The current study shows that temperature and rainfall are significantly associated with PA and ST in 10- to 12-year-old European children.

Although detrimental associations of sitting time and health indicators have been observed in young adults, evidence of pathophysiological mechanisms is lacking. Therefore, this study tested the hypothesis that the acute cardiometabolic effects of prolonged sitting can be compensated by hourly interruptions to sitting in healthy, young adults. Additionally, leg muscle activation during sitting and moderate-intensity physical activity interruptions was assessed. Eleven apparently healthy adults (18-24 yr; five men/six women) participated in this randomized, crossover study, involving two experimental conditions: 1) 8 h prolonged sitting and 2) 8 h of sitting, interrupted with hourly, 8-min, moderate-intensity cycling exercise bouts. In both conditions, participants consumed two standardized, high-fat mixed meals after 1 and 5 h. Capillary blood samples were collected hourly during each 8-h experimental condition. Muscle activity was measured using electromyography. Muscle activity during cycling was seven to eight times higher compared with rest. Postprandial levels of C-peptide were significantly lower (unstandardized regression coefficient = -0.19; confidence interval = [-0.35; -0.03]; P = 0.017) during interrupted sitting compared with prolonged sitting. Postprandial levels of other cardiometabolic biomarkers (e.g., glucose, triglycerides, cholesterol) were not significantly different between conditions. Hourly physical activity interruptions in sitting time, requiring a muscle activity of seven to eight times the resting value, led to an attenuation of postprandial C-peptide levels but not for other cardiometabolic biomarkers compared with prolonged sitting in healthy, young adults. Whether this acute effect transfers to chronic effects over time is unknown.

Bioelectrical impedance analysis (BIA) is a practical method to estimate percentage body fat (%BF). In this systematic review, we aimed to assess validity, responsiveness, reliability and measurement error of BIA methods in estimating %BF in children and adolescents.We searched for relevant studies in Pubmed, Embase and Cochrane through November 2012. Two reviewers independently screened titles and abstracts for inclusion, extracted data and rated methodological quality of the included studies. We performed a best evidence synthesis to synthesize the results, thereby excluding studies of poor quality. We included 50 published studies. Mean differences between BIA and reference methods (gold standard [criterion validity] and convergent measures of body composition [convergent validity]) were considerable and ranged from negative to positive values, resulting in conflicting evidence for criterion validity. We found strong evidence for a good reliability, i.e. (intra-class) correlations ≥0.82. However, test-retest mean differences ranged from 7.5% to 13.4% of total %BF in the included study samples, indicating considerable measurement error. Our systematic review suggests that BIA is a practical method to estimate %BF in children and adolescents. However, validity and measurement error are not satisfactory., (© 2013 The Authors. obesity reviews © 2013 International Association for the Study of Obesity.)

Background: Few studies have differentiated between weekday and weekend day sleep duration in their association with indicators of weight status in children. Therefore, we examined the association of week and weekend day sleep duration with indicators of body composition in 10-12 year old European school children., Methods and Findings: Multi-level linear regression analysis was performed to examine the association between parent-reported week and weekend day sleep duration and objectively assessed child BMI and WC, adjusting for socio-demographic variables and energy balanced related behaviours EBRBs (i.e. dietary, physical and sedentary behaviour). Compared to sleeping 10 hrs/night or more, sleeping on average less than 10 hrs/night during weekdays was associated with higher BMI (for example, B = 0.86 and CI = [0.27;1.45] when sleeping ≤7 hrs) and WC (for example, B = 1.99 and CI = [0.32;3.65] when sleeping ≤7 hrs). Sleeping 9 hrs/night during weekend days, but not ≤8 hrs, was associated with higher WC (B = 0.66; CI = [0.04;1.28]) compared to sleeping more than 10 hrs/night. Average (week and weekend) sleep duration less than 10 hrs/night was associated with higher values for BMI (B = 0.98; CI = [0.24;1.73] and WC (B = 2.35; CI = [0.08;4.31])., Conclusions: Weekday sleep duration seems more strongly associated with body composition in European school children than weekend day sleep duration. Promoting adequate sleep duration may contribute to healthy weight in children.

Background: TV time and total sedentary time have been positively related to biomarkers of cardiometabolic risk in adults. We aim to examine the association of TV time and computer time separately with cardiometabolic biomarkers in young adults. Additionally, the mediating role of waist circumference (WC) is studied., Methods and Findings: Data of 634 Dutch young adults (18-28 years; 39% male) were used. Cardiometabolic biomarkers included indicators of overweight, blood pressure, blood levels of fasting plasma insulin, cholesterol, glucose, triglycerides and a clustered cardiometabolic risk score. Linear regression analyses were used to assess the cross-sectional association of self-reported TV and computer time with cardiometabolic biomarkers, adjusting for demographic and lifestyle factors. Mediation by WC was checked using the product-of-coefficient method. TV time was significantly associated with triglycerides (B = 0.004; CI = [0.001;0.05]) and insulin (B = 0.10; CI = [0.01;0.20]). Computer time was not significantly associated with any of the cardiometabolic biomarkers. We found no evidence for WC to mediate the association of TV time or computer time with cardiometabolic biomarkers., Conclusions: We found a significantly positive association of TV time with cardiometabolic biomarkers. In addition, we found no evidence for WC as a mediator of this association. Our findings suggest a need to distinguish between TV time and computer time within future guidelines for screen time.

Background: Screen time has been associated with pediatric overweight. However, it is unclear whether overweight predicts or is predicted by excessive amounts of screen time. The aim of this study was to examine the direction of the association between screen time and body fatness in Dutch adolescents., Methods: Longitudinal data of 465 Dutch adolescents (mean age at baseline 13 years, 53% boys) was used. Body fatness (objectively measured BMI, four skin folds and waist- and hip circumference), self-reported time spent watching TV and computer use, and aerobic fitness (shuttle run test) were assessed in all participants at three time points during 12 months. Multi-level linear autoregressive analyses was used to examine whether screen time predicted body fatness in the following time period and whether body fatness predicted screen time. Analyses were performed for boys and girls separately and adjusted for ethnicity and aerobic fitness., Results: Time spent TV viewing did predict changes in BMI and hip circumference in boys, but not in girls, in the subsequent period. Computer time significantly predicted increases in skinfolds in boys and girls and increases in BMI in girls. Body fatness did not predict any changes in screen time., Conclusion: The present study only partly supports the widely posited hypothesis that higher levels of screen time cause increases in body fatness. In addition, this study demonstrates that high levels of body fatness do not predict increases in screen time.

Background: The association between objectively assessed sedentary time and metabolic risk factors in childhood have rarely been studied. Therefore, we examined the independent relationship between objectively assessed and self-rated sedentary time and indicators of metabolic health in Dutch and Hungarian 10-12 year olds., Methodology/principal Findings: We performed a cross-sectional survey in primary schools. Participants were Dutch and Hungarian girls (n = 73, aged 12.2 ± 0.6 years, 18% overweight/obese) and boys (n = 69, aged 12.2 ± 0.7 years, 38% overweight/obese). Sedentary time and physical activity were assessed by the Actigraph accelerometer. TV and PC time were assessed by self-report. Adiposity indicators included body weight, height, and waist circumference (WC). Fasting plasma glucose, C-peptide, total cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol, and triglycerides were determined in capillary blood and summed into a metabolic risk score. Linear regression analyses were adjusted for physical activity, number of sedentary bouts and WC. Children spent on average 7.6 hours of their daily waking time in sedentary behavior and self-reported 116 ± 64 min/day watching TV and 85 ± 57 min/day using the computer. Comparing the 1(st) and 4(th) quartile of objectively assessed sedentary time, C-Peptide levels, WC and BMI were significantly higher in the most sedentary quartile, while the difference in metabolic risk score was borderline significant (p = 0.09). Comparing the 1(st) and 4(th) quartile of TV time, BMI was significantly higher in the most sedentary quartile, while the difference in WC score was borderline significant (p = 0.06). In the adjusted linear regression analysis we found no significant association of sedentary time with metabolic risk., Conclusions/significance: Although BMI and WC were higher in the most sedentary versus the least sedentary children; we found no further evidence that more sedentary children were at increased metabolic risk.

Background: It is not clear whether the association between sedentary time and cardiometabolic risk exists among obese adolescents. We examined the association between screen time (TV and computer time) and cardiometabolic risk in obese Dutch adolescents., Methods and Findings: For the current cross-sectional study, baseline data of 125 Dutch overweight and obese adolescents (12-18 years) participating in the Go4it study were included. Self-reported screen time (Activity Questionnaire for Adolescents and Adults) and clustered and individual cardiometabolic risk (i.e. body composition, systolic and diastolic blood pressure, low-density (LDL-C), high-density (HDL-C) and total cholesterol (TC), triglycerides, glucose and insulin) were assessed in all participants. Multiple linear regression analyses were used to assess the association between screen time and cardiometabolic risk, adjusting for age, gender, pubertal stage, ethnicity and moderate-to-vigorous physical activity. We found no significant relationship between self-reported total screen time and clustered cardiometabolic risk or individual risk factors in overweight and obese adolescents. Unexpectedly, self-reported computer time, but not TV time, was slightly but significantly inversely associated with TC (B = -0.002; CI = [-0.003;-0.000]) and LDL-C (B = -0.002; CI = [-0.001;0.000])., Conclusions: In obese adolescents we could not confirm the hypothesised positive association between screen time and cardiometabolic risk. Future studies should consider computer use as a separate class of screen behaviour, thereby also discriminating between active video gaming and other computer activities.

Aim: Knee extensor neuromuscular activity, rectified surface electromyography (rsEMG) and single motor unit EMG was investigated during isometric (60 degrees knee angle), shortening and lengthening contractions (50-70 degrees, 10 degrees s(-1)) corrected for force-velocity-related differences in force-generating capacity. However, during dynamic contractions additional factors such as shortening-induced force losses and lengthening-induced force gains may also affect force capacity and thereby neuromuscular activity. Therefore, even after correction for force-velocity-related differences in force capacity we expected neuromuscular activity to be higher and lower during shortening and lengthening, respectively, compared to isometric contractions., Methods: rsEMG of the three superficial muscle heads was obtained in a first session [10 and 50% maximal voluntary contraction (MVC)] and additionally EMG of (46) vastus lateralis motor units was recorded during a second session (4-76% MVC). Using superimposed electrical stimulation, force-generating capacity for shortening and lengthening contractions was found to be 0.96 and 1.16 times isometric (Iso) force capacity respectively. Therefore, neuromuscular activity during submaximal shortening and lengthening was compared with isometric contractions of respectively 1.04Iso (=1/0.96) and 0.86Iso (=1/1.16). rsEMG and discharge rates were normalized to isometric values., Results: rsEMG behaviour was similar (P > 0.05) during both sessions. Shortening rsEMG (1.30 +/- 0.11) and discharge rate (1.22 +/- 0.13) were higher (P < 0.05) than 1.04Iso values (1.05 +/- 0.05 and 1.03 +/- 0.04 respectively), but lengthening rsEMG (1.05 +/- 0.12) and discharge rate (0.90 +/- 0.08) were not lower (P > 0.05) than 0.86Iso values (0.76 +/- 0.04 and 0.91 +/- 0.07 respectively)., Conclusion: When force-velocity-related differences in force capacity were taken into account, neuromuscular activity was not lower during lengthening but was still higher during shortening compared with isometric contractions.

Single motor unit electromyographic (EMG) activity of the knee extensors was investigated at different knee angles with subjects (n = 10) exerting the same absolute submaximal isometric torque at each angle. Measurements were made over a 20 degrees range around the optimum angle for torque production (AngleTmax) and, where feasible, over a wider range (50 degrees ). Forty-six vastus lateralis (VL) motor units were recorded at 20.7 +/- 17.9 %maximum voluntary contraction (%MVC) together with the rectified surface EMG (rsEMG) of the superficial VL muscle. Due to the lower maximal torque capacity at positions more flexed and extended than AngleTmax, single motor unit recruitment thresholds were expected to decrease and discharge rates were expected to increase at angles above and below AngleTmax. Unexpectedly, the recruitment threshold was higher (P < 0.05) at knee angles 10 degrees more extended (43.7 +/- 22.2 N.m) and not different (P > 0.05) at knee angles 10 degrees more flexed (35.2 +/- 17.9 N.m) compared with recruitment threshold at AngleTmax (41.8 +/- 21.4 N.m). Also, unexpectedly the discharge rates were similar (P > 0.05) at the three angles: 11.6 +/- 2.2, 11.6 +/- 2.1, and 12.3 +/- 2.1 Hz. Similar angle independent discharge rates were also found for 12 units (n = 5; 7.4 +/- 5.4 %MVC) studied over the wider (50 degrees ) range, while recruitment threshold only decreased at more flexed angles. In conclusion, the similar recruitment threshold and discharge behavior of VL motor units during submaximal isometric torque production suggests that net motor unit activation did not change very much along the ascending limb of the knee-angle torque relationship. Several factors such as length-dependent twitch potentiation, which may contribute to this unexpected aspect of motor control, are discussed.

In literature, an inconsistency exists in the submaximal exercise intensity at which type II fibers are activated. In the present study, the recruitment of type I and II fibers was investigated from the very beginning and throughout a 45-min cycle exercise at 75% of the maximal oxygen uptake, which corresponded to 38% of the maximal dynamic muscle force. Biopsies of the vastus lateralis muscle were taken from six subjects at rest and during the exercise, two at each time point. From the first biopsy single fibers were isolated and characterized as type I and II, and phosphocreatine-to-creatine (PCr/Cr) ratios and periodic acid-Schiff (PAS) stain intensities were measured. Cross sections were cut from the second biopsy, individual fibers were characterized as type I and II, and PAS stain intensities were measured. A decline in PCr/Cr ratio and in PAS stain intensity was used as indication of fiber recruitment. Within 1 min of exercise both type I and, although to a lesser extent, type II fibers were recruited. Furthermore, the PCr/Cr ratio revealed that the same proportion of fibers was recruited during the whole 45 min of exercise, indicating a rather constant recruitment. The PAS staining, however, proved inadequate to fully demonstrate fiber recruitment even after 45 min of exercise. We conclude that during cycling exercise a greater proportion of type II fibers is recruited than previously reported for isometric contractions, probably because of the dynamic character of the exercise. Furthermore, the PCr/Cr ratio method is more sensitive in determining fiber activation than the PAS stain intensity method.

The Ehlers-Danlos Syndrome (EDS) is a heterogeneous group of heritable connective tissue disorders. Skeletal muscle features belong to the clinical criteria of EDS and are generally interpreted to result from increased tendon distensibility or exercise avoidance. However, muscle function in EDS has hardly been investigated as such. We performed a pilot study consisting of clinical investigations, electromyography, muscle ultrasound, muscle biopsy, and quantitative muscle function tests on two EDS patients with deficiency of tenascin-X. Quantitative muscle function proved severely reduced despite normal findings on electromyography and muscle biopsy. These findings dispute the interpretation of increased tendon distensibility. We hypothesize that alterations in the extracellular matrix modify myofascial force transmission and thus influence muscle function in EDS.