Stuart Biddle

Relationships between media use, body fatness and physical activity in children and youth: a meta-analysis

OBJECTIVE: To review the empirical evidence of associations between television (TV) viewing, video/computer game use and (a) body fatness, and (b) physical activity.DESIGN: Meta-analysis.METHOD: Published English-language studies were located from computerized literature searches, bibliographies of primary studies and narrative reviews, and manual searches of personal archives. Included studies presented at least one empirical association between TV viewing, video/computer game use and body fatness or physical activity among samples of children and youth aged 3–18 y.MAIN OUTCOME MEASURE: The mean sample-weighted corrected effect size (Pearson r).RESULTS: Based on data from 52 independent samples, the mean sample-weighted effect size between TV viewing and body fatness was 0.066 (95% CI=0.056–0.078; total N=44 707). The sample-weighted fully corrected effect size was 0.084. Based on data from six independent samples, the mean sample-weighted effect size between video/computer game use and body fatness was 0.070 (95% CI=−0.048 to 0.188; total N=1722). The sample-weighted fully corrected effect size was 0.128. Based on data from 39 independent samples, the mean sample-weighted effect size between TV viewing and physical activity was −0.096 (95% CI=−0.080 to −0.112; total N=141 505). The sample-weighted fully corrected effect size was −0.129. Based on data from 10 independent samples, the mean sample-weighted effect size between video/computer game use and physical activity was −0.104 (95% CI=−0.080 to −0.128; total N=119 942). The sample-weighted fully corrected effect size was −0.141.CONCLUSION: A statistically significant relationship exists between TV viewing and body fatness among children and youth although it is likely to be too small to be of substantial clinical relevance. The relationship between TV viewing and physical activity is small but negative. The strength of these relationships remains virtually unchanged even after correcting for common sources of bias known to impact study outcomes. While the total amount of time per day engaged in sedentary behavior is inevitably prohibitive of physical activity, media-based inactivity may be unfairly implicated in recent epidemiologic trends of overweight and obesity among children and youth. Relationships between sedentary behavior and health are unlikely to be explained using single markers of inactivity, such as TV viewing or video/computer game use.

Health-enhancing physical activity and sedentary behaviour in children and adolescents

We provide a wide-ranging review of health-related physical activity in children and adolescents using a behavioural epidemiology framework. In contrast to many other reviews, we highlight issues associated with true sedentary behaviours alongside physically active behaviours. Specifically, we review the evidence concerning the links between physical activity and cardiovascular disease, overweight and obesity, psychosocial measures, type II diabetes, and skeletal health. Although the evidence is unconvincing at times, several factors lead to the conclusion that promoting physical activity in youth is desirable. A review of the prevalence of physical activity and sedentary behaviours shows that many young people are active, but this declines with age. A substantial number are not adequately active for health benefits and current trends in juvenile obesity are a cause for concern. Prevalence data on sedentary behaviours are less extensive but suggest that total media use by young people has not changed greatly in recent years. Most children and adolescents do not exceed recommended daily hours of TV viewing. Physical activity is unrelated to TV viewing. We also identified the key determinants of physical activity in this age group, highlighting demographic, biological, psychological, behavioural, social and environmental determinants. Interventions were considered for school, family and community environments. Finally, policy recommendations are offered for the education, governmental, sport and recreation, health, and mass media sectors.

Physical activity and mental health in children and adolescents: a review of reviews

Objective To synthesise reviews investigating physical activity and depression, anxiety, self-esteem and cognitive functioning in children and adolescents and to assess the association between sedentary behaviour and mental health by performing a brief review. Methods Searches were performed in 2010. Inclusion criteria specified review articles reporting chronic physical activity and at least one mental health outcome that included depression, anxiety/stress, self-esteem and cognitive functioning in children or adolescents. Results Four review articles reported evidence concerning depression, four for anxiety, three for self-esteem and seven for cognitive functioning. Nine primary studies assessed associations between sedentary behaviour and mental health. Physical activity has potentially beneficial effects for reduced depression, but the evidence base is limited. Intervention designs are low in quality, and many reviews include cross-sectional studies. Physical activity interventions have been shown to have a small beneficial effect for reduced anxiety, but the evidence base is limited. Physical activity can lead to improvements in self-esteem, at least in the short term. However, there is a paucity of good quality research. Reviews on physical activity and cognitive functioning have provided evidence that routine physical activity can be associated with improved cognitive performance and academic achievement, but these associations are usually small and inconsistent. Primary studies showed consistent negative associations between mental health and sedentary behaviour. Conclusions Association between physical activity and mental health in young people is evident, but research designs are often weak and effects are small to moderate. Evidence shows small but consistent associations between sedentary screen time and poorer mental health.

Sedentary time in adults and the association with diabetes, cardiovascular disease and death: systematic review and meta-analysis

Aims/hypothesisSedentary (sitting) behaviours are ubiquitous in modern society. We conducted a systematic review and meta-analysis to examine the association of sedentary time with diabetes, cardiovascular disease and cardiovascular and all-cause mortality.MethodsMedline, Embase and the Cochrane Library databases were searched for terms related to sedentary time and health outcomes. Cross-sectional and prospective studies were included. RR/HR and 95% CIs were extracted by two independent reviewers. Data were adjusted for baseline event rate and pooled using a random-effects model. Bayesian predictive effects and intervals were calculated to indicate the variance in outcomes that would be expected if new studies were conducted in the future.ResultsEighteen studies (16 prospective, two cross-sectional) were included, with 794,577 participants. Fifteen of these studies were moderate to high quality. The greatest sedentary time compared with the lowest was associated with a 112% increase in the RR of diabetes (RR 2.12; 95% credible interval [CrI] 1.61, 2.78), a 147% increase in the RR of cardiovascular events (RR 2.47; 95% CI 1.44, 4.24), a 90% increase in the risk of cardiovascular mortality (HR 1.90; 95% CrI 1.36, 2.66) and a 49% increase in the risk of all-cause mortality (HR 1.49; 95% CrI 1.14, 2.03). The predictive effects and intervals were only significant for diabetes.Conclusions/interpretationSedentary time is associated with an increased risk of diabetes, cardiovascular disease and cardiovascular and all-cause mortality; the strength of the association is most consistent for diabetes.

The Transtheoretical Model of behavior change: A meta-analysis of applications to physical activity and exercise

The purpose of this study was to summarize findings from empirical applications of the transtheoretical model (TTM) (Prochaska & DiClemente, 1983) in the physical activity domain by using the quantitative method of meta-analysis. Ninety-one independent samples from 71 published reports were located that present empirical data on at least one core construct of the TTM applied to exercise and physical activity. In general, results support the application because core constructs differ across stages and most changes are in the direction predicted by the theory. Three general conclusions are offered. First, existing data are unable to confirm whether physical activity behavior change occurs in a series of stages that are qualitatively different or along adjacent segments of an underlying continuum. Second, the growing number of studies that incorporate TTM concepts means that there is an increasing need to standardize and improve the reliability of measurement. Finally, the role of processes of change needs reexamining because the higher order constructs are not apparent in the physical activity domain and stage-by-process interactions are not evident. There now are sufficient data to confirm that stage membership is associated with different levels of physical activity, self-efficacy, pros and cons, and processes of change. Further studies that simply stage participants or examine cross-sectional differences between core constructs of the TTM are of limited use. Future research should examine the moderators and mediators of stage transition.

An assessment of self-reported physical activity instruments in young people for population surveillance: Project ALPHA

BackgroundThe assessment of physical activity is an essential part of understanding patterns and influences of behaviour, designing interventions, and undertaking population surveillance and monitoring, but it is particularly problematic when using self-report instruments with young people. This study reviewed available self-report physical activity instruments developed for use with children and adolescents to assess their suitability and feasibility for use in population surveillance systems, particularly in Europe.MethodsSystematic searches and review, supplemented by expert panel assessment.ResultsPapers (n = 437) were assessed as potentially relevant; 89 physical activity measures were identified with 20 activity-based measures receiving detailed assessment. Three received support from the majority of the expert group: Physical Activity Questionnaire for Children/Adolescents (PAQ-C/PAQ-A), Youth Risk Behaviour Surveillance Survey (YRBS), and the Teen Health Survey.ConclusionsPopulation surveillance of youth physical activity is strongly recommended and those involved in developing and undertaking this task should consider the three identified shortlisted instruments and evaluate their appropriateness for application within their national context. Further development and testing of measures suitable for population surveillance with young people is required.

Sedentary behavior and dietary intake in children, adolescents and adults: A systematic review.

CONTEXT Sedentary behavior is implicated in youth and adult overweight and obesity. However, the relationship between sedentary behavior and weight status is often small or inconsistent, with few studies controlling for confounding factors such as diet and physical activity. Diet has been hypothesized to covary with some sedentary behaviors. It is opportune, therefore, to review whether dietary intake is associated with sedentary behavior in young people and adults. This may allow for better interpretation of the diversity of findings concerning sedentary behavior and weight status. EVIDENCE ACQUISITION Published English-language studies were located from computerized and manual searches in early 2010. Included studies were observational studies assessing an association between at least one sedentary behavior and at least one aspect of dietary intake in children (aged <11 years), adolescents (aged 12-18 years), or adults (aged >18 years). EVIDENCE SYNTHESIS Fifty-three studies, totaling 111 independent samples, were eligible for this review. Sedentary behavior in children (n=19, independent samples=24), adolescents (n=26, independent samples=72), and adults (n=11, independent samples=14) appears to be clearly associated with elements of a less healthy diet including lower fruit and vegetable consumption; higher consumption of energy-dense snacks, drinks, and fast foods; and higher total energy intake. Strengths of association were mainly in the small-to-moderate range. CONCLUSIONS The association drawn mainly from cross-sectional studies is that sedentary behavior, usually assessed as screen time and predominantly TV viewing, is associated with unhealthy dietary behaviors in children, adolescents, and adults. Interventions need to be developed that target reductions in sedentary time to test whether diet also changes.

Tracking of sedentary behaviours of young people: a systematic review.

OBJECTIVE To review the empirical evidence concerning the strength of tracking of sedentary behaviours from childhood and adolescence. METHODS Published English language studies were located from computerised and manual searches in 2009. Included studies were prospective, longitudinal studies with at least one sedentary behaviour for at least two time-points, with tracking coefficients reported, and included children (aged 3-11 years) and adolescents (12-18 years) at baseline. RESULTS Based on data from 21 independent samples, tracking coefficients (r) ranged from 0.08 (over 16 years) to 0.73 (over 2 years) for TV viewing, from 0.18 (boys over 3 years) to 0.52 (over 2 years) for electronic game/computer use, from 0.16 (girls over 4 years) to 0.65 (boys over 2 years) for total screen time, and from -0.15 (boys over 2 years) to 0.48 (over 1 year) for total sedentary time. Study follow-up periods ranged from 1 to up to 27 years, and tracking coefficients tended to be higher with shorter follow-ups. CONCLUSIONS Sedentary behaviours track at moderate levels from childhood or adolescence. Data suggest that sedentary behaviours may form the foundation for such behaviours in the future and some may track slightly better than physical activity.

Physical activity and sedentary behaviours in youth: issues and controversies

There is growing concern over the effects of sedentary lifestyles on the health of young people. Recent rapid increases in juvenile obesity have received a great deal of attention in the scientific and popular press and have been attributed partly to television viewing, computer games and other sedentary behaviours. These are thought to compete with physical activity. There is a ‘moral panic’ concerning the ‘couch kids’ culture in modern western society. Project STIL (Sedentary Teenagers and Inactive Lifestyles) at Loughborough University is investigating ‘what young people do’ and focuses on active and inactive pursuits chosen in their leisure time. The following issues are addressed in this paper with specific reference to young people: how do we define ‘sedentary behaviour’ and do key sedentary behaviours displace physical activity? Are key sedentary behaviours obesogenic? What are the secular trends for children and youth for TV viewing? Our results for young people suggest that:1. TV viewing and video-game playing are largely uncorrelated with physical activity, suggesting that there is time for both2. meta-analytic findings show that body fatness is not related in any clinically meaningful way with key sedentary behaviours3. although more children and youth have greater access to TVs than in previous generations, the amount of TV watched per head has not changed for 40 years. Preliminary findings from Project STIL suggest that inactivity is more complex than we sometimes think. Indeed, measures of ‘couch potato-ism’, such as TV viewing, may be inappropriate markers of inactivity.

Research methods in sport and exercise psychology: quantitative and qualitative issues

Contemporary aspects of research methods in sport and exercise psychology are discussed in this wide-ranging review. After an introduction centred on trends in sport and exercise psychology methods, the review is organized around the major themes of quantitative and qualitative research. Our aim is to highlight areas that may be problematic or controversial (e.g. stepwise statistical procedures), underused (e.g. discriminant analysis), increasingly used (e.g. meta-analysis, structural equation modelling, qualitative content analysis) and emergent (e.g. realist tales of writing). Perspectives range from the technical and speculative to the controversial and critical. While deliberately not providing a ‘cookbook’ approach to research methods, we hope to provide enough material to help researchers to appreciate the diversity of potential methods and to adopt a more critical perspective in their own research consumption and production.