Temporal relationships between screen-time and physical activity with cardiorespiratory fitness in English schoolchildren: a 2-year longitudinal study

The Effect of Sedentary Behaviour on Cardiorespiratory Fitness: A Systematic Review and Meta-Analysis

BACKGROUND

Cardiorespiratory fitness (CRF) is an important indicator of current and future health. While the impact of habitual physical activity on CRF is well established, the role of sedentary behaviour (SB) remains less understood.

OBJECTIVE

We aimed to determine the effect of SB on CRF.

METHODS

Searches were conducted in MEDLINE, Embase, PsycINFO, CINAHL and SPORTDiscus from inception to August 2022. Randomised controlled trials, quasi-experimental studies and cohort studies that assessed the relationship between SB and CRF were eligible. Narrative syntheses and meta-analyses summarised the evidence, and Grading of Recommendations, Assessment, Development and Evaluation (GRADE) certainty was based on evidence from randomised controlled trials.

RESULTS

This review included 18 studies that focused on youth (four randomised controlled trials, three quasi-experimental studies, 11 cohort studies) and 24 on adult populations (15 randomised controlled trials, five quasi-experimental studies, four cohort studies). In youth and adults, evidence from randomised controlled trials suggests mixed effects of SB on CRF, but with the potential for interventions to improve CRF. Quasi-experimental and cohort studies also support similar conclusions. Certainty of evidence was very low for both age groups. A meta-analysis of adult randomised controlled trials found that interventions targeting reducing SB, or increasing physical activity and reducing SB, had a significant effect on post-peak oxygen consumption (mean difference = 3.16 mL.kg-1.min-1, 95% confidence interval: 1.76, 4.57).

CONCLUSIONS

Evidence from randomised controlled trials indicates mixed associations between SB and CRF, with the potential for SB to influence CRF, as supported by meta-analytical findings. Further well-designed trials are warranted to confirm the relationship between SB and CRF, explore the effects of SB independent from higher intensity activity, and investigate the existence of such relationships in paediatric populations.

CLINICAL TRIAL REGISTRATION

PROSPERO CRD42022356218.

Effect of Excessive Screen Time on Cardiorespiratory Fitness in Children: A Longitudinal Study

Background: This study investigated the effect of different components of screen time (mobile phone use, TV/video viewing, and video gaming) on cardiorespiratory fitness (CRF) development in children aged 9–12 years. Methods: This was a two-year longitudinal study conducted with 175 children (49.7% girls, mean age = 9.5) in Japan. CRF was assessed using a 20 m shuttle run test conducted at baseline and again at follow-up. Children were categorized as “Good” or “Poor” based on the change in CRF scores for each gender. Screen time was assessed using a self-reported questionnaire at baseline and termed as “high” if children reported ≥ 2 h/day. Univariate and multivariate logistic regression analyses were performed after adjusting for gender, physical activity, and time of data collection. Results: Children scoring “high” on mobile phone use had lower odds of being categorized as “Good” in CRF change (crude odds ratio (OR): 0.34; 95% confidence interval (CI): 0.15–0.90 (adjusted OR: 0.33; 95% CI: 0.12–0.91)). There were no significant effects of TV/video viewing (crude OR: 1.54; 95% CI: 0.84–2.81) and video gaming (crude OR: 0.98; 95% CI: 0.48–1.97) on changes in CRF. Conclusions: Limiting excessive mobile phone usage might be important for ensuring healthy development of CRF in children.

Relationship between Moderate-to-Vigorous Physical Activity with Health-Related Physical Fitness Indicators among Pakistani School Adolescents: Yaali-Pak Study

Background

The current study is the foremost study exploring the relationships between moderate-to-vigorous physical activity and health-related physical fitness indicators among 12-16-year-old adolescents of the South Punjab region of Pakistan.

Methods

The researcher adopted the cross-sectional research design for the study. A total of 2970 participants (1477 boys and 1493 girls) aged adolescents from South Punjab, Pakistan, completed health-related physical fitness indicators measuring strength, endurance, and aerobic capacity through a hand-grip strength test, modified pull-up test, plank test, and 20-m shuttle run test, and physical activity were subjectively assessed by International Physical Activity Questionnaire Short Form (IPAQ-SF). Linear regression models were used to explore the between moderate-to-vigorous physical activity (MVPA) with health-related physical fitness indicators.

Results

Positive associations were observed between hand-grip strength (p < 0.001), modified pull-up (p < 0.001), plank exercise (p < 0.001), and 20-m shuttle run test (p < 0.001), with MVPA. The gender-specific comparison also indicated a significant (p < 0.001) and positive relationship. The results revealed that as MVPA increases, body composition, muscular strength, core muscular endurance, and aerobic capacity could improve in both genders.

Conclusions

MVPA appears to be an effective and reliable predictor of health-related physical fitness among school adolescents.

The Combinations of Physical Activity, Screen Time, and Sleep, and Their Associations with Self-Reported Physical Fitness in Children and Adolescents

Much evidence has indicated that adherence to the 24 h movement guidelines (physical activity, screen time and sleep) is associated with physical health, while little is known about the adherence to the 24 h movement guidelines and self-reported physical fitness in adolescents. This study, therefore, aims to explore the association between the 24 h movement guidelines (in isolation or combination) and self-reported physical fitness in a sample of Chinese adolescents in an age range of 10-17.

METHODS

A convenient sample of 3807 children and adolescents from 12 schools was adopted in the present study. A questionnaire based on the Health Behaviour in School-aged Children was used to assess physical activity and screen time, and the Pittsburgh Sleep Scale was utilized to measure sleep duration. The International Fitness Scale was used to assess physical fitness in study participants. Ordinal logistic regression was performed to estimate the association between adherence to the 24 h movement guidelines and self-reported physical fitness.

RESULTS

Of all study participants, 0.9% of them met the 24 h movement guidelines, and meeting the guidelines was significantly associated with higher levels of self-reported physical fitness. The analysis for the association between specific combinations of 24 h movement guidelines and self-reported physical fitness underscored the importance of meeting the physical activity recommendations.

CONCLUSION

Adherence to more recommendations contained in the 24 h movement guidelines was associated with higher self-reported physical fitness, especially cardiorespiratory fitness and muscular strength. Our study also stressed the importance of promoting moderate to vigorous physical activity in children and adolescents. Further works should focus on the association of a recommendation of adherence with other health indicators and replicate this study on larger samples among Chinese children and adolescents. Additionally, longitudinal or interventional studies that include more socio-demographic factors are needed to explore the association between 24 h movement guidelines and self-reported physical fitness, and the 24 h movement guidelines also should be promoted on a large scale in Chinese children and adolescents. Moreover, it is also needed to gain better insights into the directionality of the relationship between compliance with 24 h movement guidelines and self-reported physical fitness, as well as the mechanisms underlying the associations in Chinese children and adolescents.

Personal, social, and environmental correlates of physical activity and sport participation in an adolescent Turkish population

Background

Benefits of physical activity has been shown for adolescents; however, there is a decline trend in number of adolescents meeting current WHO recommendations. This trend underlines the importance of identifying factors associated with adolescents’ physical activity level (PAL) with considerations of regional and cultural differences to plan and implement effective policies. Therefore, the aim of this study was to determine personal, ecological, and social factors associated with PAL and sport participation in Turkish adolescents aged 11–14 years. A cross-sectional study was conducted by including 996 adolescents aged between 11 and 14 years from 39 secondary schools in İstanbul, Turkey. Logistic regression analyses performed to identify the significant personal (age, gender, sleep time, screen time, BMIz score, having siblings), ecological (presence of playground, type of school transportation), and social (family income, engaging a physical activity with family, and preferred activity at school breaks) predictors of PAL and sport participation.

Results

Adolescents who were active during break time at school (p < 0.001), engaging a physical activity with family (p < 0.001), and did not have a sibling (p = 0.029) were more likely to be physically active. Adolescents behaved active during break time at school (p < 0.001), had a playground at home (p < 0.001), spending time with family for physical activity (p < 0.001), and did not have a sibling (p = 0.021) were more likely to participate in a sport activity.

Conclusions

Predictors of PAL in this study indicates the need to promote active break time in school, increased physical activity time with family, and to design environmental policies to increase number of playgrounds.

Relationship Between the Practice of Physical Activity and Physical Fitness in Physical Education Students: The Integrated Regulation As a Mediating Variable

The practice of physical activity (PA) contributes to the prevention of chronic diseases such as obesity, metabolic syndrome or cardiovascular diseases, being also directly related to the individual’s physical fitness. Therefore, it is necessary to measure and monitoring the levels of PA in childhood and adolescence, since it may be useful to describe their current health status and the association with physical fitness, as well as to reveal putative consequences in the future. Within the educational field, it has been shown that physical education (PE) classes are a favorable context for the creation of healthy physical-sports habits and self-determined motivation could be a key for explaining the level of PA practice. For this reason, the purpose of this research was to study the mediating role of integrated regulation (IR) on the relationship between PA and physical fitness in children and adolescents. A total of 325 students between 11 and 14 years old participated in the study. The level of PA was estimated through the specific Physical Activity Questionnaire for Children (PAQ-C), while motivation and IR were measured by using the Perceived Locus of Causality scale (PLOC-2). In addition, physical fitness was measured through the Eurofit fitness battery of tests, composed of three body composition measures and seven tests of different physical capacities. The physical fitness score showed no differences when genders were compared. After regression analysis, the resulting models revealed a good adjustment and correlation between PA practice and physical fitness (β = 0.173; p < 0.001), being established through the macro Process that this relationship is partially conditioned by the IR (β = 0.122; p = 0.03). ROC curve analysis estimated the score of 5.88 as a cut-off point to discriminate between levels of IR for students, classified as physically active or not (AUC = 0.67; p < 0.001). The conclusions from these main and other complementary analyses reporting complete mediations, suggest that the IR could be decisive in predicting and explaining the relationship between the practice of PA and physical fitness at these ages, highlighting its importance for a greater adherence to the practice.

Cardiorespiratory Fitness in Youth: An Important Marker of Health: A Scientific Statement From the American Heart Association

Cardiorespiratory fitness (CRF) refers to the capacity of the circulatory and respiratory systems to supply oxygen to skeletal muscle mitochondria for energy production needed during physical activity. CRF is an important marker of physical and mental health and academic achievement in youth. However, only 40% of US youth are currently believed to have healthy CRF. In this statement, we review the physiological principles that determine CRF, the tools that are available to assess CRF, the modifiable and nonmodifiable factors influencing CRF, the association of CRF with markers of health in otherwise healthy youth, and the temporal trends in CRF both in the United States and internationally. Development of a cost-effective CRF measurement process that could readily be incorporated into office visits and in field settings to screen all youth periodically could help identify those at increased risk.

Barriers and enablers to physical activity and aerobic fitness deficits among childhood cancer survivors

BACKGROUND

Physical activity and aerobic fitness are modifiable risk factors for cardiovascular disease (CVD) after childhood cancer. How survivors engage in physical activity remains unclear, potentially increasing CVD risk. We assessed survivors' physical activity levels, barriers and enablers, fitness, and identified predictors of fitness and physical activity stage of change.

METHODS

Childhood cancer survivors (CCS; 8-18 years old) ≥1 year post-treatment were assessed for aerobic fitness (6-min walk test), used to extrapolate VO_2max , and body composition (InBody 570). Survivors self-reported physical activity to determine stage of change (Patient-Centered Assessment and Counselling for Exercise). Physical activity and fitness were compared with guidelines and CVD-risk cut-points (VO_2max  < 42 mL/kg/min: males; VO_2max  < 35 mL/kg/min: females). Multiple regression and mediator-moderator analysis were used to identify fitness predictors and stage of change.

RESULTS

One hundred two survivors (12.8 ± 3.3 years) participated (46% acute lymphoblastic leukaemia). Forty percent of males (VO_2max  = 43.3 ± 6.3 mL/kg/min) and 28% of females (VO_2max  = 36.5 ± 5.9 mL/kg/min) were in the CVD-risk category, while 25% met physical activity guidelines. Most prevalent physical activity barriers were fatigue (52%), preferring television instead of exercise (38%), and lacking time (34%). Predictive factors for reduced fitness included being older, female, higher waist-to-height ratio, higher screen time, and moderated by lower physical activity (r²  = 0.91, P < .001). Survivors with higher physical activity stage of change were male, lower body fat percentage, lower screen time, and lived with both parents (r = 0.42, P = .003).

CONCLUSION

Aerobic fitness and physical activity of CCS is low compared with population norms, potentially increasing CVD risk. Addressing physical activity barriers and enablers, including reducing screen time, could promote regular physical activity, reducing CVD risk.

Moderate-to-vigorous physical activity attenuates the detrimental effects of television viewing on the cardiorespiratory fitness in Asian adolescents: the Asia-fit study

BACKGROUND

Moderate-to-vigorous physical activity (MVPA) and television viewing are independently associated with cardiorespiratory fitness. However, limited evidence is available on their combined effects, specifically of MVPA and watching television, on cardiorespiratory fitness in the young Asian population. Therefore, the present study examined whether MVPA can attenuate the detrimental effects of prolonged television viewing on the cardiorespiratory fitness of Asian adolescents.

METHODS

This is a cross-sectional study on 9553 adolescents (aged 12-15 years) from 8 Asian metropolitan cities (Tokyo, Hong Kong, Shanghai, Taipei, Bangkok, Kuala Lumpur, Seoul, and Singapore). Cardiorespiratory fitness was assessed by using a 15-m progressive aerobic capacity endurance run (PACER) test. The time spent on MVPA and watching television was assessed using the International Physical Activity Questionnaire-Short Form.

RESULTS

MVPA was more closely associated with the PACER score than the duration of watching television. Compared with the reference group (i.e. those with the lowest levels of MVPA [< 30 min/day] and the most sedentary [≥3 h/day of television time]), PACER scores were significantly higher for those who met the physical activity recommendation (≥60 min/day in MVPA), regardless of the duration of television viewing. Conversely, girls in the least active group (< 30 min/day of MVPA) who watched television < 1 h/day demonstrated better PACER scores than the reference group.

CONCLUSIONS

Sufficient MVPA (≥60 min/day) can attenuate the detrimental effects of excessive television viewing with cardiorespiratory fitness in Asian adolescents. In addition, the duration of television viewing had significant but weaker associations with cardiorespiratory fitness compared to MVPA.

Association Between Sitting, Screen Time, Fitness Domains, and Fundamental Motor Skills in Children Aged 5-16 Years: Cross-Sectional Population Study

BACKGROUND

To examine the associations between school-age children's sedentary behavior, screen time, and 3 physical activity attributes: muscular strength, cardiorespiratory endurance (CRE), and fundamental movement skills.

METHODS

Cross-sectional survey of 2734 children in years 2 and 4 and 3671 adolescents in years 6, 8, and 10. Total sitting time, 6 screen time behaviors, and physical activity were measured by self-report. Muscular strength was assessed by standing broad jump; CRE by 20-m shuttle run test; and fundamental movement skills by process-oriented checklists. Associations between incremental sitting and screen time (in hours) and meeting the healthy zone of physical activity attributes were examined using logistic regression.

RESULTS

After adjusting for covariates and physical activity, children had lower odds of achieving the healthy zone for muscular strength and CRE for each hour of week (but not weekend) screen time. For adolescents, each hour of screen time per day was associated with lower odds of achieving the healthy fitness zone for CRE, locomotor skills, and overall healthy zone, and each hour of weekend screen time was associated with lower odds of achieving the healthy zone for most attributes and overall healthy zone. The associations were slightly stronger among adolescent girls than boys. The findings were similar for total sitting time.

CONCLUSIONS

Screen time was associated with a lower likelihood to achieve healthy zones of physical activity attributes, and the effect was more consistent and slightly stronger among adolescents than children. This may suggest that the negative effects of screen time are incremental, emerging during adolescence.

Relationship Among Changes in Sedentary Time, Physical Activity, and Body Mass Index in Young Schoolchildren: A 3-Year Longitudinal Study

PURPOSES

To examine the association between sedentary time (ST) and light physical activity (LPA), moderate- to vigorous-intensity physical activity (MVPA), and body mass index (BMI), and to track these behaviors over a 3-year follow-up in young schoolchildren.

METHODS

The final sample was 64 children (female: n = 36 or 56.3%), enrolled in schools in Porto, Portugal. Height and mass of children were measured by standard methods, and BMI was then calculated. ST, LPA, and MVPA were measured by accelerometer. Changes (Δ) and relative changes (Δ%) between 2009/2010 and 2012/2013 of ST, LPA, MVPA, and BMI were computed. Multiple linear regression analyses were fit to predict Δ%ST (outcome variable), by Δ%LPA, Δ%MVPA, and Δ%BMI (exposure variables).

RESULTS

ST increased and LPA decreased significantly for whole sample (both Ps < .05). No statistically significant difference was found for MVPA over time. There were no differences for ΔST, ΔLPA, ΔMVPA, and ΔBMI between boys and girls. The Δ%LPA and Δ%MVPA were negatively associated with Δ%ST, whereas Δ%BMI was positively associated. Tracking coefficients varied from moderate to strong.

CONCLUSIONS

Time spent in ST increases due to displacement of time in LPA. This reinforces public health measures and suggests the need for interventions focusing on offsetting the decline ST and increasing MVPA during childhood.

Behavior Tracking and 3-Year Longitudinal Associations Between Physical Activity, Screen Time, and Fitness Among Young Children

PURPOSE

Understanding the correlates of children's fitness as they develop is needed. The objectives of this study were to 1) examine the longitudinal associations between physical activity (PA), screen time (ST), and fitness; 2) determine if sex moderates associations; and 3) track PA and ST over 3 years.

METHODS

Findings are based on 649 children [baseline = 4.5 (0.5) y; follow-up = 7.8 (0.6) y] from Edmonton, Canada. Parental-reported hour per week of PA and ST were measured at baseline and 3 years later. Fitness (vertical jump, sit and reach, waist circumference, grip strength, predicted VO_2max, push-ups, and partial curl-ups) was measured using established protocols at follow-up. Sex-specific z scores or low/high fitness groups were calculated. Linear or logistic multiple regression models and Spearman correlations were conducted.

RESULTS

Baseline ST was negatively associated with follow-up grip strength [β = -0.010; 95% confidence interval (CI), -0.019 to -0.001]. Associations between baseline PA and follow-up overall fitness (β = 0.009; 95% CI, 0.002 to 0.016) were significant, whereas baseline PA and follow-up VO_2max (β = 0.014; 95% CI, 0.000 to 0.027) approached significance (P < .06). No sex interactions were observed. Moderate and large tracking were observed for PA (r_s = .30) and ST (r_s = .53), respectively.

CONCLUSIONS

PA and ST may be important modifiable correlates of overall fitness in young children.

Relationship between Physical Activity and Physical Fitness in Preschool Children: A Cross-Sectional Study

PURPOSE

To evaluate the relationships between objectively measured physical activity and physical fitness among preschool children.

METHODS

A total of 346 participants (201 boys and 145 girls) aged 3.5-5.5 years (M = 4.5 yr, SD = 0.47) from Shanghai, China, completed physical fitness assessments, including triceps skinfold thickness (TSFT), grip strength, tennis throwing, sit and reach test, standing long jump, balance beam, 10mSRT, and 20mSRT. Physical activity was objectively measured by ActiGraphGT3X+ accelerometer. Multiple linear regression models were used to explore the cross-sectional associations between PA and physical fitness after adjusting for age, gender, BMI, and valid wearing time.

RESULTS

Positive associations were observed between stand long jump (p < .01), tennis throwing (p < .01), laps in 20mSRT (p < .01), and MVPA. However, TSFT (p < .05), time in 10mSRT (p < .01), and balance beam (p < .05) were negatively associated with MVPA. Furthermore, positive associations were found between stand long jump (p < .01), tennis throwing (p < .01), and MVPA only in boys. Negative associations were found between time on balance beam (p < .01) and MVPA only in girls.

CONCLUSIONS

MVPA appears to be an effective and reliable predictor of preschoolers' physical fitness. Boys' body composition, muscular strength, explosive strength, agility, aerobic fitness, girls' agility, aerobic fitness, and balance could improve as MVPA increases.

An evidence-update on the prospective relationship between childhood sedentary behaviour and biomedical health indicators: a systematic review and meta-analysis

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.

Sedentary behavior during school-time: Sociodemographic, weight status, physical education class, and school performance correlates in Brazilian schoolchildren

OBJECTIVES

To investigate whether sedentary behavior during school-time is associated with gender, age, mother's education, having physical education classes, weight status, and academic performance.

DESIGN

Cross-sectional study.

METHODS

A sample of 571 children (7-12 years old) from five elementary schools in Florianopolis, South Brazil had their height and weight measured, and wore accelerometers during class time. Teachers completed a form to evaluate children's reading and writing skills. Parents provided sociodemographic and educational information. Data was analyzed using multilevel linear regression analyses.

RESULTS

Children spent an average of 132min in sedentary behavior during school-time (64% of total school-time). Girls (137.5min), obese children (138.1min), older children (144.2min), and those who did not have physical education classes (140.2min) spent more time engaged in sedentary activities than their peers. Academic performance and mother's education were not associated with sedentary behaviors.

CONCLUSIONS

Children spent most of their school-time in sedentary activities, with girls, older students, and obese students being even more sedentary than their peers. Physical education classes were a protective factor against excessive sedentary behavior in school. Interventions for reducing sedentary behavior during school-time could employ additional strategies to benefit the at risk groups. In addition, encouraging student's participation in physical education classes could minimize the time spent in sedentary behavior during school hours.

Media device ownership and media use: Associations with sedentary time, physical activity and fitness in English youth

The aim of this study was to determine whether ownership and use of electronic media were associated with sedentary time and cardiorespiratory fitness (fitness) in youth. We also aimed to determine if associations were independent of physical activity (PA).

Fitness was measured using the 20 m shuttle-run. PA, sedentary time, ownership of media devices and media use were self-reported.

Participants (n = 678, age 10–15 years) reported daily sedentary time of 620 (± 210) min. Forty-one percent of participants had low PA and 50.4% had low fitness.

Higher weekend sedentary time was associated with low fitness in girls (p = 0.005) and boys (p < 0.001) and remained significant when adjusted for PA in the latter (p = 0.006). Using social media was associated with higher sedentary time in both sexes and low fitness in girls. High sedentary time was more likely (OR = 5.3, 95%CI: 2.0–14.4) in boys who owned game consoles. Low fitness was more likely in boys who owned digital/satellite TV receivers (OR = 1.8, 95%CI: 1.8–3.2).

Schoolchildren spent > 10 h or ~ 85% of each waking day sedentary. Use of social media was associated with higher sedentary time in both sexes and with low fitness in girls. Reducing social media use in youth offers one potential target for intervention. Behaviours associated with sedentary time differed from predictors of low fitness. The complex and often sex-specific interactions identified between sedentary time, PA and fitness suggest the need for carefully targeted interventions to reduce sedentary time and improve fitness in English youth.

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English schoolchildren spend most of their waking time engaged in sedentary behaviours.

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Physical activity and sedentary time are independently associated with low fitness in boys.

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Owning a game console is associated with higher sedentary time in boys.

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Use of social media is associated with higher sedentary time in boys and girls.

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Owning a digital/satellite TV receiver doubles the risk of low cardiorespiratory fitness in boys.

Systematic review of sedentary behaviour and health indicators in school-aged children and youth: an update

This systematic review is an update examining the relationships between objectively and subjectively measured sedentary behaviour and health indicators in children and youth aged 5–17 years. EMBASE, PsycINFO, and Medline were searched in December 2014, and date limits were imposed (≥February 2010). Included studies were peer-reviewed and met the a priori-determined population (apparently healthy children and youth, mean age: 5–17 years), intervention (durations, patterns, and types of sedentary behaviours), comparator (various durations, patterns, and types of sedentary behaviours), and outcome (critical: body composition, metabolic syndrome/cardiovascular disease risk factors, behavioural conduct/pro-social behaviour, academic achievement; important: fitness, self-esteem) study criteria. Quality of evidence by outcome was assessed using the Grading of Recommendations Assessment, Development, and Evaluation framework. Due to heterogeneity, a narrative analysis was conducted. A total of 235 studies (194 unique samples) were included representing 1 657 064 unique participants from 71 different countries. Higher durations/frequencies of screen time and television (TV) viewing were associated with unfavourable body composition. Higher duration/frequency of TV viewing was also associated with higher clustered cardiometabolic risk scores. Higher durations of TV viewing and video game use were associated with unfavourable behavioural conduct/pro-social behaviour. Higher durations of reading and doing homework were associated with higher academic achievement. Higher duration of screen time was associated with lower fitness. Higher durations of screen time and computer use were associated with lower self-esteem. Evidence ranged from “very low” to “moderate” quality. Higher quality studies using reliable and valid sedentary behaviour measures should confirm this largely observational evidence.

Sex-specific associations of moderate and vigorous physical activity with physical fitness in adolescents

The present study examined the sex-specific associations of moderate and vigorous physical activity (VPA) with physical fitness in 300 Japanese adolescents aged 12-14 years. Participants were asked to wear an accelerometer to evaluate physical activity (PA) levels of various intensities (i.e. moderate PA (MPA), 3-5.9 metabolic equivalents (METs); VPA, ≥6 METs; moderate to vigorous PA (MVPA), ≥3 METs). Eight fitness items were assessed (grip strength, bent-leg sit-up, sit-and-reach, side step, 50 m sprint, standing long jump, handball throw, and distance running) as part of the Japanese standardised fitness test. A fitness composite score was calculated using Japanese fitness norms, and participants were categorised according to their score from category A (most fit) to category E (least fit), with participants in categories D and E defined as having low fitness. It was found that for boys, accumulating more than 80.7 min/day of MVPA may reduce the probability of low fitness (odds ratio (ORs) [95% confidence interval (CI)] = 0.17 [0.06-0.47], p = .001). For girls, accumulating only 8.4 min of VPA could reduce the likelihood of exhibiting low fitness (ORs [95% CI] = 0.23 [0.05-0.89], p = .032). These results reveal that there are sex-specific differences in the relationship between PA and physical fitness in adolescents, suggesting that sex-specific PA recommendation may be needed to improve physical fitness in adolescents.

Validity and reliability of a modified english version of the physical activity questionnaire for adolescents

Background

Adaptation of physical activity self-report questionnaires is sometimes required to reflect the activity behaviours of diverse populations. The processes used to modify self-report questionnaires though are typically underreported. This two-phased study used a formative approach to investigate the validity and reliability of the Physical Activity Questionnaire for Adolescents (PAQ-A) in English youth. Phase one examined test content and response process validity and subsequently informed a modified version of the PAQ-A. Phase two assessed the validity and reliability of the modified PAQ-A.

Methods

In phase one, focus groups (n = 5) were conducted with adolescents (n = 20) to investigate test content and response processes of the original PAQ-A. Based on evidence gathered in phase one, a modified version of the questionnaire was administered to participants (n = 169, 14.5 ± 1.7 years) in phase two. Internal consistency and test-retest reliability were assessed using Cronbach’s alpha and intra-class correlations, respectively. Spearman correlations were used to assess associations between modified PAQ-A scores and accelerometer-derived physical activity, self-reported fitness and physical activity self-efficacy.

Results

Phase one revealed that the original PAQ-A was unrepresentative for English youth and that item comprehension varied. Contextual and population/cultural-specific modifications were made to the PAQ-A for use in the subsequent phase. In phase two, modified PAQ-A scores had acceptable internal consistency (α = 0.72) and test-retest reliability (ICC = 0.78). Modified PAQ-A scores were significantly associated with objectively assessed moderate-to-vigorous physical activity (r = 0.39), total physical activity (r = 0.42), self-reported fitness (r = 0.35), and physical activity self-efficacy (r = 0.32) (p ≤ 0.01).

Conclusions

The modified PAQ-A had acceptable internal consistency and test-retest reliability. Modified PAQ-A scores displayed weak-to-moderate correlations with objectively measured physical activity, self-reported fitness, and self-efficacy providing evidence of satisfactory criterion and construct validity, respectively. Further testing with more diverse English samples is recommended to provide a more complete assessment of the tool.

Electronic supplementary material

The online version of this article (doi:10.1186/s13690-016-0115-2) contains supplementary material, which is available to authorized users.

Screen time impairs the relationship between physical fitness and academic attainment in children

OBJECTIVE

The purpose of this study was twofold: to analyze the association between physical fitness and academic attainment, and to determine the influence of screen time on the association between physical fitness and academic attainment.

METHODS

A cross-sectional study including 395 schoolchildren from seven schools of the Maule Region, Chile (mean age 12.1 years; 50.4% boys) participated in the autumn of 2014 (March to June). Self-reported physical activity and screen time were evaluated. The study measured academic achievement (mean of the grades obtained in several core subjects), physical fitness (cardiorespiratory fitness and muscular strength), weight, height, parental education, and socioeconomic status. Linear regression analysis was used to analyze the relationships between physical fitness and academic attainment after adjusting for potential confounders by gender. Analysis of variance was used to analyze the differences in academic attainment according to fitness and screen time categories (< 2 hours/day and ≥ 2 hours/day).

RESULTS

In both genders good cardiorespiratory fitness levels were associated with high language (β=0.272-0.153) and mean academic attainment (β=0.192-0.156) grades; however, after adjusting for screen time and other potential confounders, these associations disappear. Similarly, no relationship was observed after analyzing those children who spend more hours of screen time (≥ 2 hours/day).

CONCLUSIONS

Academic attainment is associated with higher cardiorespiratory fitness levels; however, it was weakly impaired by screen time. These findings seem to suggest that parents and policymakers should minimize the negative effects of screen time on children's lives to maximize the beneficial effect of healthy habits on academic attainment.

Effects of reallocating time in different activity intensities on health and fitness: a cross sectional study

BACKGROUND

The effects of replacing time in specific activity categories for other categories (e.g. replacing sedentary time with light activity) on health and fitness are not well known. This study used isotemporal substitution to investigate the effects of substituting activity categories in an equal time exchange fashion on health and fitness in young people.

METHODS

Participants were drawn from schools in Camden, London (n = 353, mean age 9.3 ± 2.3 years). Time sedentary, in light and in moderate-to-vigorous activity (MVPA) was measured via accelerometry. The effects of substituting time in activity categories (sedentary, light and MVPA) with equivalent time in another category on health and fitness were examined using isotemporal substitution.

RESULTS

In single and partition models, MVPA was favourably associated with body fat %, horizontal jump distance and flexibility. Time sedentary and in light activity were not associated with health and fitness outcomes in these models. In substitution models, replacing one hour of sedentary time with MVPA was favourably associated with body fat % (B = -4.187; 95% confidence interval (CI), -7.233, -1.142), horizontal jump distance (B = 16.093; 95% CI, 7.476, 24.710) and flexibility (B = 4.783; 95% CI, 1.910, 7.656). Replacing time in light activity with MVPA induced similar benefits but there were null effects for replacing sedentary with light intensity.

CONCLUSION

Substituting time sedentary and in light activity with MVPA was associated with favourable health and fitness. Time in sedentary behaviour may only be detrimental to health and fitness when it replaces time in MVPA in young people.

Pathway from central obesity to childhood asthma. Physical fitness and sedentary time are leading factors

RATIONALE

Available prospective studies of obesity and asthma have used only body mass index (BMI) as an indicator for adiposity; studies using detailed obesity measures are lacking, and the role of physical fitness level and sedentary time remains unexplored in the link between obesity and asthma.

OBJECTIVES

To compare various anthropometric measures of obesity in relation to childhood asthma, and to further characterize the interrelations among central obesity, physical fitness level, sedentary time, and asthma.

METHODS

The nationwide Taiwan Children Health Study followed 2,758 schoolchildren from fourth to sixth grade, annually collecting data regarding physical fitness, sedentary time, obesity measures (comprising body weight and height, abdominal and hip circumference, skin fold thickness, and body composition), asthma, and pulmonary function tests. The generalized estimating equation was used for 3 years of repeated measurements to analyze the interrelation among obesity, sedentary time, physical fitness level, and asthma; a structural equation model was used to explore the pathogenesis among these factors. Asthma incidence was analyzed during a 2-year follow-up among centrally obese and nonobese groups in baseline children without asthma.

MEASUREMENTS AND MAIN RESULTS

Central obesity most accurately predicts asthma. Low physical fitness levels and high screen time increase the risk of central obesity, which leads to asthma development. Obesity-related reduction in pulmonary function is a possible mechanism in the pathway from central obesity to asthma.

CONCLUSIONS

Central obesity measures should be incorporated in childhood asthma risk predictions. Children are encouraged to increase their physical fitness levels and reduce their sedentary time to prevent central obesity-related asthma.

Does participation in physical education reduce sedentary behaviour in school and throughout the day among normal-weight and overweight-to-obese Czech children aged 9-11 years?

Participation of 9 to 11-year-old children in physical education lessons (PEL) contributes to a significantly higher duration of moderate-to-vigorous physical activity (MVPA) during the school day and, in overweight/obese girls and normal-weight boys, to an increase in overall daily MVPA as shown by previous research. However, it is not known whether this increase in MVPA is at the expense of light physical activity (LPA) or sedentary behaviour (SED). SED, LPA, and MVPA were assessed in 338 schoolchildren aged 9–11 years (50.3% girls; 29.6% overweight/obese) over two school days (with and without a PEL) using a triaxial accelerometer during various segments of the school day. SED, LPA, and MVPA were quantified based on the duration of the activity (minutes). Participation in PEL led to significantly higher school MVPA in the overweight/obese and normal-weight girls and boys (p < 0.005) compared to MVPA of those children on the school day without PEL. Participation in PEL led to a significantly higher overall daily MVPA duration compared to that during the day without PEL for the overweight/obese girls (p < 0.05), normal-weight girls (p < 0.05) and boys (p < 0.005). Participation in PEL contributed not only to significantly higher LPA in the normal-weight girls and boys (p < 0.01) during the school day but also reduced school-time SED in the overweight/obese children (p < 0.01) and normal-weight girls (p < 0.005). Moreover, participation in PEL significantly reduced the overall daily SED in the normal-weight children and overweight/obese boys (p < 0.05). Adding one PEL to the daily school routine appears to be a promising strategy for effectively reducing SED in children.

Correlates of weight gain in German children attending elementary school

OBJECTIVE

To examine the association of physical fitness, sports participation, physical activity and sedentary behavior as well as dietary patterns and family background with weight gain in non-overweight elementary school children, independent of absolute body weight.

METHODS

Height, weight, and physical fitness were assessed in 1249 (51% male) children in south-west Germany during the fall of 2010 and 2011 (age at baseline: 7.0±0.6years). Based on changes in body mass index percentiles children were classified into a weight loss, constant weight, or weight gain group. Health behavior and family background were assessed via parent questionnaire. Group differences were examined via analysis of variance and multinomial logistic regression.

RESULTS

Weight gain was associated with low physical activity, lack of active transport, and lack of regular breakfast at follow-up. Children in the weight gain category also displayed lower fitness during baseline and follow-up, but differences were more pronounced during follow-up. TV time, migration background or parental education was not associated with weight gain.

CONCLUSION

Ensuring adequate physical activity and high fitness is an important aspect in the prevention of excessive weight gain during childhood. In addition to sports participation active transport should be emphasized in future weight management programs in children.

Fatores associados ao comportamento sedentário em escolares de 9-12 anos de idade

São recentes os estudos que investigaram impactos do comportamento sedentário (CS) sobre a saúde, principalmente em crianças. O objetivo foi investigar fatores associados ao CS em escolares do município de Uberaba, MG. Trata-se de estudo epidemiológico, transversal, com amostra probabilística (n = 649). Foram coletadas e consideradas variáveis independentes: medidas antropométricas, pressão arterial, exames bioquímicos, tempo gasto em atividade física (AF). CS foi considerado variável dependente, caracterizado pelo tempo de tela (TT), e verificado fatores associados pela regressão de Poisson. Meninas apresentaram valores maiores de dobras cutâneas, triglicerídeos e HDL-c e meninos, maior concentração de glicose sanguínea, atenderam mais à recomendação de 60 min de AF/dia e maior CS. O TT > 2 h/dia foi prevalente em 76,9 % da amostra. CS não foi associado a variáveis sociodemográficas, de saúde e comportamentais em crianças de 9-12 anos de idade. Mais pesquisas são necessárias para elucidar as inter-relações complexas entre TT e fatores associados.

Sedentary Behavior and Health Outcomes in Children and Adolescents

The purpose of this review was to summarize findings from epidemiological studies that determined if sedentary behavior was associated with obesity, metabolic risk factors, and cardiorespiratory fitness in children and adolescents. We noted if studies adjusted for moderate-to-vigorous physical activity (MVPA), dietary intakes, and/or sleep duration. Articles were identified through PubMed using the search terms: (sedentary OR sitting OR television) AND (adiposity OR blood pressure OR body mass index OR cardiometabolic OR metabolic risk OR waist circumference). The search was limited to ages 6 to 18 years, humans, and published between January 1, 2008 and September 26, 2012. Cross-sectional and longitudinal studies observed associations between more sedentary behavior, especially screen-based sedentary behavior, and measures of obesity; and most associations were independent of MVPA and dietary intake. Cross-sectional and longitudinal studies reported associations between screen-based sedentary behavior and lower cardiorespiratory fitness, and most associations were independent of MVPA and obesity. Cross-sectional studies observed associations between more screen-based and objectively measured sedentary behavior and lower insulin sensitivity; and most associations were independent of MVPA and obesity. There was little-to-no evidence that sedentary behavior was associated with increased blood pressure and increased blood lipids.