24-Hour movement behaviors and executive functions in preschoolers: A compositional and isotemporal reallocation analysis.

This cross-sectional study explored the relationship between 24-hour movement behaviors and executive function (EF) in preschool children. A total of 426 Han Chinese preschoolers (231 males; 3.8 ± 0.6 years old) from Zhuhai, Guangdong Province, China were selected from October 2021 to December 2021. Accelerometers were used to measure physical activity (PA) and sedentary behavior (SB), while sleep duration was obtained via a parent-report questionnaire. Components of EF (cognitive flexibility, inhibitory control, and working memory) were assessed using computerized behavioral tasks. The daily composition was significantly associated with inhibitory control and working memory. Inhibitory control improvements were linked to the addition of moderate-to-vigorous physical activity (MVPA) at the expense of SB and sleep. The reallocation between MVPA, SB, sleep, and light physical activity yielded a significant association with working memory.

Associations of school physical activity environment with comorbid obesity and myopia in children and adolescents: Findings from a Chinese national follow-up study.

BACKGROUND: Overweight and obesity (OWOB) and myopia have become two of the most important issues affecting the health of children and adolescents worldwide. Despite the recognition that the school physical activity (PA) environment is a critical factor for preventing and controlling overweight, obesity (OWOB), and myopia in children and adolescents, research on OWOB and myopia as a comorbidity remains unexplored, with evidence for effective strategies still being inconclusive. Hence, this study aimed to assess the prevalence and progression of comorbid OWOB/myopia and each condition alone, and to explore the association with school PA environment. METHODS: A total of 9814 children and adolescents aged 6-18 years were included from the Chinese National Survey on Students' Constitution and Health follow-up survey conducted from November 2019 to November 2020 in China. Anthropometric measurements, unaided distance vision acuity and non-cycloplegic refraction data were collected to assess OWOB and myopia, while eight indicators from questionnaires for children and adolescents aged 9-18 years were investigated to assess school PA environment. We calculated the one-year incidence and progression rates of comorbid OWOB/myopia, OWOB alone, and myopia alone. Mixed effect logistic regression was evaluated the association between school PA environment and incidence and progression of comorbid OWOB/myopia, OWOB, and myopia. RESULTS: The prevalence of comorbid OWOB/myopia increased from 11.1% in 2019 to 17.9% in 2020, and the incidence of comorbid OWOB/myopia was 10.9%. Children and adolescents experiencing an unfavorable school PA environment had a higher risk of the incidence of comorbid OWOB/myopia compared to a favorable school environment (OR = 1.85, 95% CI: 1.42-2.42). Similar findings were seen in the incidence of obesity (OR = 1.86, 95% CI: 1.26-2.75). Children and adolescents in an unfavorable school PA environment had a higher risk of myopia progression (OR = 1.29, 95% CI: 1.01-1.65). CONCLUSIONS: Obesity and myopia and their comorbidity have been serious among children and adolescents in China. A favorable school PA environment might mitigate the risk of comorbid OWOB/myopia, OWOB, and myopia progression.

24-H movement behaviors and physical fitness in preschoolers: A compositional and isotemporal reallocation analysis.

Background/Objectives: This study examined the relationships between 24-h movement behaviors and physical fitness (PF) in preschool children. Methods: The study was conducted on 474 children aged 3-6 years in Zhuhai. Physical activity (PA) and sedentary behavior (SB) were collected by the accelerometer, and sleep time was assessed through the parent-report questionnaire. Balance, cardiorespiratory fitness (CRF), flexibility, muscle strength, muscular endurance, and speed-agility were measured using a balance beam test, 20 m shuttle run test, sit and reach test, handgrip test, sit-ups, and 4 × 10 m shuttle run test respectively. The compositional data analysis was used to examine the association between 24-h movement behaviors and PF, and the compositional isotemporal substitution analysis was used for the time reallocation. Results: The daily composition, adjusted for age, gender, and body mass index (BMI), was significantly associated with CRF (p < 0.001, r2 = 0.20), flexibility (p < 0.001, r2 = 0.07), muscular strength (p < 0.001, r2 = 0.37), muscular endurance (p < 0.001, r2 = 0.26), and speed-agility (p < 0.001, r2 = 0.26). The addition of moderate-to-vigorous PA (MVPA) at the expense of SB and sleep, MVPA at the cost of sleep, was associated with significant muscular strength and speed-agility improvements respectively. The impact of SB and sleep replacing MVPA is stronger than MVPA replacing SB and sleep on muscular strength. Conclusion: These findings offer useful insight for the replacement of movement behaviors within the recommended range to facilitate PF development in early childhood.

Secular trend and urban-rural disparity for age at spermarche among Chinese Han boys from 1995 to 2019.

AIM: To examine the secular trend and the urban-rural disparity of spermarche among Chinese Han boys from 1995 to 2019. METHODS: A total of 392 775 boys of Han ethnicity aged 11-18 years were extracted from the 1995, 2000, 2005, 2010, 2014 and 2019 Chinese National Surveys on Students' Constitution and Health. The median age at spermarche was estimated using the status quo data and probit analysis. The chi-square, ANOVA and LSD tests were used to compare the differences between the year-subgroups. U-test was used to compare the difference between urban and rural areas at each year. RESULTS: The median age at spermarche in Chinese Han boys decreased from 14.6 years in 1995 to 13.9 years in 2019 (p < 0.001). The rural boys showed a faster decreasing pace with a 1-year advance of age at spermarche while the urban boys had only a 0.5-year decrement, and there was still a statistically significant difference between urban-rural areas in 2019 (p < 0.001). Similar to urban-rural disparity, the age gap at spermarche between areas with different urbanisation rates became smaller over time. CONCLUSIONS: In general, spermarche in Chinese Han boys showed a decreasing trend, but the pace was slowing down. The urban-rural disparity in puberty development still existed but was gradually narrowing.

The mean age of menarche among Chinese schoolgirls declined by 6 months from 2005 to 2014.

AIM: This study assessed the trends in the age at menarche in Chinese schoolgirls from the majority Han group and 21 ethnic minorities from 2005 to 2014. We also compared the group differences during the study period. METHODS: A total of 344 230 girls aged 9-18 years were extracted from the 2005, 2010 and 2014 Chinese National Survey on Students' Constitution and Health. The age at menarche for each subgroup was estimated by probit analysis. The chi-square test and Z-test were used to compare the differences between the groups. RESULTS: The overall average age at menarche in Chinese schoolgirls decreased from 12.8 years in 2005 to 12.3 years in 2014. The Han girls and girls from 17 ethnic minorities showed decreasing trends in the age at menarche, while four ethnic minorities demonstrated fluctuating increasing trends over time. The gaps in age at menarche between the Han group and 14 of the ethnic minorities became smaller over the study period and were similar by 2014. CONCLUSION: The overall findings were a decrease in the age at menarche in China and smaller gaps between the majority Han group and ethnic minority groups. Ethnic-specific public health policies are urgently needed on issues such as contraception.

Item response modeling: a psychometric assessment of the children's fruit, vegetable, water, and physical activity self-efficacy scales among Chinese children.

BACKGROUND: This study aimed to evaluate the psychometric properties of four self-efficacy scales (i.e., self-efficacy for fruit (FSE), vegetable (VSE), and water (WSE) intakes, and physical activity (PASE)) and to investigate their differences in item functioning across sex, age, and body weight status groups using item response modeling (IRM) and differential item functioning (DIF). METHODS: Four self-efficacy scales were administrated to 763 Hong Kong Chinese children (55.2% boys) aged 8-13 years. Classical test theory (CTT) was used to examine the reliability and factorial validity of scales. IRM was conducted and DIF analyses were performed to assess the characteristics of item parameter estimates on the basis of children's sex, age and body weight status. RESULTS: All self-efficacy scales demonstrated adequate to excellent internal consistency reliability (Cronbach's α: 0.79-0.91). One FSE misfit item and one PASE misfit item were detected. Small DIF were found for all the scale items across children's age groups. Items with medium to large DIF were detected in different sex and body weight status groups, which will require modification. A Wright map revealed that items covered the range of the distribution of participants' self-efficacy for each scale except VSE. CONCLUSIONS: Several self-efficacy scales' items functioned differently by children's sex and body weight status. Additional research is required to modify the four self-efficacy scales to minimize these moderating influences for application.

Prevalence of overweight in Hong Kong Chinese children: Its associations with family, early-life development and behaviors-related factors.

BACKGROUND: Childhood overweight is a crucial public health concern. Recognizing its associated factors can facilitate the establishment of effective prevention strategies. The aim of the present study was to examine the prevalence of overweight in Hong Kong Chinese children and explore its influential factors in relation to family, early-life development and behavior-related issues. METHODS: A cross-sectional study was conducted in 894 primary school students aged 9-12 years (50.4% boys). Self-reported information on family background (parental body weight, education, employment status, household income, living space, and bedroom situation), early-life developmental variables (birth weight, gestational age and feeding pattern), and children's lifestyle factors (sleep, various eating behaviors and physical activity) were collected with a questionnaire. A logistic regression was performed to test the associations. RESULTS: The overweight prevalence in Hong Kong children was 19.9%. Compared to the girls, the boys were more overweight (23.5% vs. 16.3%). Overweight was linked to paternal overweight, maternal overweight, lower maternal education, less monthly household income, and shorter sleep duration. Compared to the breast-fed children, those who were not breast-fed were more likely to become overweight, with marginal significance. CONCLUSION: The present study revealed a high prevalence of overweight in Hong Kong pediatric population and demonstrated the family resemblance in weight status. Further interventions and promotions should involve parents and consider the family as a unit to tackle childhood overweight.

The Effects of Text Message Content on the Use of an Internet-Based Physical Activity Intervention in Hong Kong Chinese Adolescents.

This study examined the effects of text message content (generic vs. culturally tailored) on the login rate of an Internet physical activity program in Hong Kong Chinese adolescent school children. A convenience sample of 252 Hong Kong secondary school adolescents (51% female, 49% male; M age = 13.17 years, SD = 1.28 years) were assigned to one of 3 treatments for 8 weeks. The control group consisted of an Internet physical activity program. The Internet plus generic text message group consisted of the same Internet physical activity program and included daily generic text messages. The Internet plus culturally tailored text message group consisted of the Internet physical activity program and included daily culturally tailored text messages. Zero-inflated Poisson mixed models showed that the overall effect of the treatment group on the login rates varied significantly across individuals. The login rates over time were significantly higher in the Internet plus culturally tailored text message group than the control group (ß = 46.06, 95% CI 13.60, 156.02; p = .002) and the Internet plus generic text message group (ß = 15.80, 95% CI 4.81, 51.9; p = .021) after adjusting for covariates. These findings suggest that culturally tailored text messages may be more advantageous than generic text messages on improving adolescents' website login rate, but effects varied significantly across individuals. Our results support the inclusion of culturally tailored messaging in future online physical activity interventions.

Pedometer-determined physical activity patterns in a segmented school day among Hong Kong primary school children.

BACKGROUND/OBJECTIVE: This study aimed to characterize pedometer-determined physical activity (PA) patterns in segmented school days among Hong Kong primary school children. METHODS: Participants were instructed to wear pedometers for 4 consecutive days. The overall step counts and counts at specific periods (e.g., after school, recess, and lunch) during the test days were recorded. RESULTS: Of the 74 recruited participants, 68 (41.2% boys, aged 10 and 11 years old) provided valid data. The mean total daily steps over the 4 test days ranged from 9064 to 9714 (standard deviation = 3140-3471 steps). The periods that contributed most toward total daily steps were after school (34.2%), recess (14.0%), and physical education (PE) classes (12.3%). Overall, Student t tests revealed that boys were more active than girls. More active children (daily step average above the sex-specific median value) accumulated significantly more steps during recess and after school than less active children (daily step average below the sex-specific median value) in both sexes (mean differences ranged from 507 steps to 1977 steps). A mixed model analysis of variance (ANOVA) revealed that students accumulated 914 steps more on days that included PE classes than on days without PE classes. A three-way ANOVA found no significant differences in body weight status (normal weight vs. overweight and obesity) and travel mode (active vs. passive modes). CONCLUSION: The findings provide a better understanding of PA patterns and the contribution of the distinct segments within a school day to children's PA. This information may assist in developing more effective, appropriate, and timely school-based PA interventions for children in Hong Kong.

Cardiorespiratory fitness attenuates the association between fatness and cardiometabolic risk in Chinese children.

Background: Childhood obesity tends to persist into adulthood, predisposing individuals to cardiometabolic risk (CMR). This study aims to investigate the mediating role of cardiorespiratory fitness (CRF) in the associations between multiple fatness indicators and individual CMR markers and clustered CMR-score, and explore sex differences. Methods: We recruited 1,557 children (age: 8 to 10, male/female: 52.7%/47.3%) in September 2022 in Ningbo, China. Physical examinations, overnight fasting blood test, and CRF was evaluated. The CMR-score was calculated by summing age- and sex-specific z scores of four CMR markers, including mean arterial blood pressure, triglycerides, the total cholesterol to high-density lipoprotein cholesterol ratio, and homeostatic model assessment for insulin resistance. Generalized linear mixed models were used to identify the associations, mediation analyses were performed to dissect the function of CRF. Results: Partial correlation analyses revealed positive associations between high fatness indicators (including body mass index [BMI], BMI z score, body fat mass index [BFMI] and waist-to-height ratio [WHtR]) and increased CMR markers, whereas high CRF was associated with decreased CMR markers (all P < 0.05). In the mediation analyses, CRF emerged as a partial mediator, attenuating the relationship between four fatness indicators and CMR-score. Specifically, CRF mediated 6.5%, 7.7%, 5.3%, and 12.5% of the association between BMI, BMI z score, BFMI, WHtR and CMR-score (all P < 0.001). And the mediating effects of CRF between WHtR and four individual CMR markers was particularly robust, ranging from 10.4% to 21.1% (all P < 0.05). What's more, CRF mediates the associations between WHtR and CMR-score more pronounced in girls than boys with a mediation effect size of 17.3% (P < 0.001). Conclusion: In Chinese children, CRF partially mitigates the adverse effects of fatness on CMR, underscoring the significance of enhancing CRF in children.

Combined Effect of Outdoor Time and Other Modifiable Factors on Myopia Incidence Among Children and Adolescents - 9 PLADs, China, 2020.

What is already known about this topic?: Myopia has been identified as a significant emerging challenge and policy priority among children and adolescents in China by the Ministry of Education and seven other departments. Limited research has been conducted to investigate the collective impact of outdoor time and other modifiable factors on the incidence of myopia. What is added by this report?: This study provides support for the protective effect of combining increased outdoor time with other prevention strategies in reducing the incidence of myopia. The results indicate the presence of a dose-response relationship. What are the implications for public health practice?: To effectively prevent myopia, it is important to implement comprehensive interventions that encompass various aspects such as outdoor time, eye-use habits, eye-use environments, and lifestyle modifications.

Do acute and chronic physical activity interventions affect the cognitive function of preschool children? A meta-analysis.

This meta-analysis aims to investigate the effects of acute and chronic physical activity (PA) interventions on multiple domains of cognitive function (CF) in preschool children. Electronic databases (PsycINFO, PubMed, SPORTDiscus, Embase, Web of Science, MEDLINE, and ERIC) were searched for relevant studies between January 2000 and February 2022. Studies that examined the effects of acute or chronic physical activity interventions on CF in preschool children aged 2-6 years were included. A total of 16 articles were eligible for this meta-analysis. Results showed that there was no effect of acute PA interventions on CF (Hedges' g = 0.04; 95% CI = -0.12, 0.19). Chronic PA interventions had a moderate and positive effect on overall CF (Hedges' g = 0.49; 95% CI = 0.29, 0.69), a large effect on perception (Hedges' g = 1.19; 95% CI = 0.64, 1.75), and a moderate effect on inhibitory control (Hedges' g = 0.73; 95% CI = 0.22, 1.24). The moderator analyses showed that overall CF performance was significantly moderated by intervention modality and assessment of cognitive outcomes, and no other moderator (study design, sample size, frequency, duration, and session length) was found to have an effect. Chronic PA intervention might be a promising way to promote multiple aspects of CF, especially executive function and perception. Future studies should explore the effect of different intensities of PA on the CF of preschool children to discern the most effective PA prescription to, in turn, enhance the CF of preschool children.

Association between early life exposure to the great famine and possible sarcopenia in older Chinese adults: a national cross-sectional study.

OBJECTIVES: We used data from the China Health and Retirement Longitudinal Study (CHARLS) to investigate how an early life famine exposure affected possible sarcopenia (PS) and to explore the extent to which a sex difference exists in the association among older Chinese adults, as well as whether risk factors modify the association. DESIGN: Cross-sectional study. SETTING: 28 provinces of China. PARTICIPANTS: Considering that the Great Chinese Famine lasted from the spring of 1959 to the fall of 1961, 3557 participants were selected and categorised into four subgroups based on their date of birth: unexposed group (1 October 1962 to 30 September 1964), fetal exposed group (1 October 1959 to 30 September 1961), infant exposed group (1 January 1958 to 31 December 1958) and preschool exposed group (1 January 1956 to 31 December 1957). OUTCOME MEASURE: PS was defined as having low muscle strength or low physical performance. METHODS: We used multivariable logistic models to analyse the association between early life famine exposure and the risk of PS in elderly life. RESULTS: The prevalences of PS among individuals in the unexposed, fetal, infant and preschool exposed groups were 15.1%, 14.4%, 23.6% and 21.9%, respectively. Compared with the unexposed group, the infant (OR: 1.55; 95% CI 1.17 to 2.05) and preschool exposed (OR: 1.46; 95% CI 1.17 to 1.82) groups exhibited significantly higher risks of PS. In men, the infant (OR: 2.15; 95% CI 1.40 to 3.31) and preschool exposed (OR: 1.78; 95% CI 1.23 to 2.57) groups were more likely to have PS, but no significant increase was seen in women. In both sexes, prevalence of PS was unrelated to early life famine exposure in the urban, underweight and normal weight subgroups. CONCLUSIONS: Early life exposure to the Great Chinese Famine was associated with a higher risk of PS in older adults. Keeping normal nutritional status in elderly life might help avoid the risk of PS, whatever the effect of early famine exposure.

Associations between exposure to ambient particulate matter and advanced liver fibrosis in Chinese MAFLD patients.

BACKGROUND & AIMS: Liver fibrosis is an important feature in patients with metabolic dysfunction-associated fatty liver disease (MAFLD). This study aimed to explore the association between long-term ambient particulate matter (PM) exposure and advanced liver fibrosis (ALF) in MAFLD participants. METHODS: A cross-sectional study of 23170 adults recruited from 33 provinces of China from 2010 to 2020. ALF was detected using the nonalcoholic fatty liver disease fibrosis score (NFS). The annual average levels of particulate matter with aerodynamic diameters of ≤ 1 µm (PM1), ≤ 2.5 µm (PM2.5) and ≤ 10 µm (PM10) were calculated using validated spatiotemporal models. Generalized additive models were applied to analyze the association between PM and ALF in patients with MAFLD. RESULTS: One-year exposure to higher levels of all PM was found to increase the risk of ALF, with odds ratios (ORs) of 1.10 (95% CI 1.06-1.14), 1.05 (1.03-1.07), and 1.03(1.02-1.04) for each 10 µg/m3 increase in PM1, PM2.5 and PM10, respectively. With the dissection of the impact of PM1 in PM2.5, PM2.5 in PM10 and PM1 in PM10, we found that PM2.5 had a stronger impact on ALF (both Pinteraction＜0.05) in comparison with PM1 and PM10. CONCLUSIONS: Long-term exposure to PM is associated with ALF in patients with MAFLD, with PM2.5 playing a dominant role.

Artificial Light-at-Night Exposure and Overweight and Obesity across GDP Levels among Chinese Children and Adolescents.

BACKGROUND: Evidence in adults suggests that exposure to artificial light-at-night (ALAN) leads to obesity. However, little is known about whether this effect exists in children and adolescents. We aimed to investigate whether ALAN exposure was associated with overweight and obesity in school-aged children and adolescents and whether this association varied with socioeconomic status. METHODS: Data on the height and weight of 129,500 children and adolescents aged 10-18 years from 72 cities were extracted from the 2014 Chinese National Survey on Students' Constitution and Health (CNSSCH). The ALAN area percentage and average ALAN intensity were calculated using the Visible/Infrared Imager/Radiometer Suite. The subjects were separated into three categories based on the cities' gross domestic product per capita (GDPPC). A mixed-effect logistic regression model and generalized additive model (GAM) were utilized to evaluate the association between ALAN exposure and overweight and obesity in children and adolescents stratified by municipal GDPPC. RESULTS: Both ALAN area (OR = 1.194, 95% CI: 1.175-1.212) and ALAN intensity (OR = 1.019, 95% CI: 1.017-1.020) were positively associated with overweight and obesity in children and adolescents, and the associations remained robust after adjusting for covariates. ORs for overweight and obesity and ALAN area decreased as GDPPC level increased (first tertile: OR = 1.457, 95% CI: 1.335-1.590; second tertile: OR = 1.350, 95% CI: 1.245-1.464; third tertile: OR = 1.100, 95% CI: 1.081-1.119). Similar results were observed for ALAN intensity. In the GAM models, thresholds existed in almost all these spline trends, indicating that ALAN might have a nonlinear association with overweight and obesity. CONCLUSIONS: ALAN contributed to the development of overweight and obesity in children and adolescents and this effect differed with GDPPC. Future longitudinal studies should confirm the causal relationship between ALAN and obesity. Moreover, reducing unnecessary exposure to artificial light at night may have beneficial implications for controlling childhood and adolescent obesity, particularly in low-income areas.

Association of fast-food restaurants with overweight and obesity in school-aged children and adolescents: A systematic review and meta-analysis.

We aimed to explore associations between the accessibility of fast-food restaurants (FFRs) and weight-related outcomes in children and adolescents through a systematic review and meta-analysis of studies. We searched three databases for studies published before October 21, 2022. Study quality was assessed using the National Institutes of Health's Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Meta-analysis was performed, and the leave-one-out method was used for sensitivity analysis. A total of 60 studies were included. According to our analysis, FFRs within a smaller buffer radius from residences or that provide unhealthy foods may have a more significant influence on children's and adolescents' weight. Children of younger ages and girls may have a higher possibility of being overweight due to FFRs. Though we could hardly avoid bias, the estimates in low-and middle-income countries (only six studies) are much higher than those in high-income countries (54 studies). More research analyses based on microscope data and individual economic levels are needed. This study yields quantitative results, provides policymakers and urban planners with a theoretical support for building resilient and sustainable human settlements, and promotes the translation of research findings from public health to environmental planning.

The effectiveness of Facebook as a social network intervention to increase physical activity in Chinese young adults.

Introduction: Facebook, one of the worlds' most popular online social networks, is easy to access and cost-effective. Its use to enhance individual's physical activity (PA) participation should be examined. This research reviews the effectiveness and successful features of Facebook for influencing PA behaviors in young adults (Study 1), and empirically examines the efficacy of the features purported in increase PA via a Facebook intervention (Study 2). Methods: In Study 1, PubMed, Medline, SPORT Discus, ERIC, and Embase were searched for articles that identified successful features and effectiveness of Facebook PA interventions published between January 2005 and February 2022. In Study 2, a 4-week Facebook PA intervention with University students was conducted using features identified in Study 1. The PA behaviors with objective (ActiGraph) and subjective (questionnaire) measures, perceived PA level, stage of readiness, effectiveness, and efficiency of Facebook were examined. Results: Study 1 concluded that the most effective strategies for producing significant PA changes in young adults using a PA Facebook intervention included the following: Adding behavior modification (goal setting and self-monitoring), using influence agents, recruiting members of an existing network with the snowball technique, being attentive to group size, enhancing social support with motivational quotes, interactive posts, opinion polls, increasing tailored feedback, and providing educational information. Study 2 found no significant difference in PA between the intervention and the control groups, as measured objectively, but the subjective reporting of PA behavior was higher in the intervention group. Compared to the control group, the Facebook PA intervention group reported more positive change in perceived stage of readiness in PA participation, commuting type, sport type, sport venue, sport emotion, and fast breathing or sweating. When features were ranked by the Facebook PA intervention group, motivation (supports from your friends) and tailored feedback (the responses from your friends are really personal and fits you) were the top two ranked features. Conclusion: The use of influence agents in the Facebook PA intervention could address exercise preference and facilitate higher program engagement. Significant differences related to commuting type, sport types, sport venue barriers, and exercise intensity across groups were noteworthy and warrant additional investigation in the future.

A systematic review of information and communication technology-based interventions for promoting physical activity behavior change in children and adolescents.

BACKGROUND: A growing body of research has employed information and communication technologies (ICTs) such as the Internet and mobile phones for disseminating physical activity (PA) interventions with young populations. Although several systematic reviews have documented the effects of ICT-based interventions on PA behavior, very few have focused on children and adolescents specifically. OBJECTIVES: The present review aimed to systematically evaluate the efficacy and methodological quality of ICT-based PA interventions for children and adolescents based on evidence from randomized controlled trials. METHODS: Electronic databases Medline, PsycInfo, CINAHL, and Web of Science were searched to retrieve English language articles published in international academic peer-reviewed journals from January 1, 1997, through December 31, 2009. Included were articles that provided descriptions of interventions designed to improve PA-related cognitive, psychosocial, and behavioral outcomes and that used randomized controlled trial design, included only children (6-12 years old) and adolescents (13-18 years old) in both intervention and control groups, and employed Internet, email, and/or short message services (SMS, also known as text messaging) as one or more major or assistive modes to deliver the intervention. RESULTS: In total, 9 studies were analyzed in the present review. All studies were published after 2000 and conducted in Western countries. Of the 9 studies, 7 demonstrated positive and significant within-group differences in at least one psychosocial or behavioral PA outcome. In all, 3 studies reported positive and significant between-group differences favoring the ICT group. When between-group differences were compared across studies, effect sizes were small in 6 studies and large in 3 studies. With respect to methodological quality, 7 of the 9 studies had good methodological quality. Failure to report allocation concealment, blinding to outcome assessment, and lack of long-term follow-up were the criteria met by the fewest studies. In addition, 5 studies measured the intervention exposure rate and only 1 study employed objective measures to record data. CONCLUSION: The present review provides evidence supporting the positive effects of ICTs in PA interventions for children and adolescents, especially when used with other delivery approaches (ie, face-to-face). Because ICT delivery approaches are often mixed with other approaches and these studies sometimes lack a comparable control group, additional research is needed to establish the true independent effects of ICT as an intervention delivery mode. Although two-thirds of the studies demonstrated satisfactory methodological quality, several quality criteria should be considered in future studies: clear descriptions of allocation concealment and blinding of outcome assessment, extension of intervention duration, and employment of objective measures in intervention exposure rate. Due to the small number of studies that met inclusion criteria and the lack of consistent evidence, researchers should be cautious when interpreting the findings of the present review.

Three days of static stretching within a warm-up does not affect repeated-sprint ability in youth soccer players.

This study aimed to examine the repeated-sprint ability (RSA) in soccer players after 3 days of static stretching. Twenty soccer players (age: 16.8 ± 0.4 years) participated in 2 series of experiments with within-subject repeated-measure design (control series [CON]: 13-minute aerobic warm-up; and static-stretching series [SS]: 10-minute aerobic warm-up and 3-minute static stretching). Each series consisted of 5 days, and RSA (9 × 30 m separated by 25-second passive recovery) was tested on days 1 and 5. Static stretching was performed for 3 consecutive days from days 2-4, before and after intermittent aerobic endurance exercise on each day. The same warm-up protocol was used before and after all RSA tests and exercises within 1 series. No significant difference between CON and SS was observed (p > 0.05) in RSA for overall (all sprints), early phase (first to third sprints), middle phase (fourth to sixth sprints), and final phase (seventh to ninth sprints). Short-term static stretching had trivial effects (Cohen's d < 0.35) on overall and split RSA phases (early, middle, and final). The present study showed that performing static stretching for 3 consecutive days and before repeated-sprint test did not negatively affect RSA. However, it is premature to recommend that static stretching could be included in in-season daily warm-up routine because some movements such as jump and single sprint were more sensitive to static stretching.

Short Durations of Static Stretching when Combined with Dynamic Stretching do not Impair Repeated Sprints and Agility.

This study aimed to compare the effect of different static stretching durations followed by dynamic stretching on repeated sprint ability (RSA) and change of direction (COD). Twenty-five participants performed the RSA and COD tests in a randomized order. After a 5 min aerobic warm up, participants performed one of the three static stretching protocols of 30 s, 60 s or 90 s total duration (3 stretches x 10 s, 20 s or 30 s). Three dynamic stretching exercises of 30 s duration were then performed (90 s total). Sit-and-reach flexibility tests were conducted before the aerobic warm up, after the combined static and dynamic stretching, and post- RSA/COD test. The duration of static stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit-and-reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p ≤ 0.001). However there were no significant differences in RSA and COD performance between the 3 stretching conditions. The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects. Furthermore, the short duration (≤ 90 s) static stretching may not have provided sufficient stimulus to elicit performance impairments. Key pointsThe duration of combined static and dynamic stretching had a positive effect on flexibility with 36.3% and 85.6% greater sit and reach scores with the 60 s and 90 s static stretching conditions respectively than with the 30 s condition (p ≤ 0.001).No significant differences in RSA and COD between the 3 stretching conditions.The lack of change in RSA and COD might be attributed to a counterbalancing of static and dynamic stretching effects.The short duration (≤ 90 s) static stretching may not have provided sufficient stimulus to elicit performance impairments.