How many adults have sufficient muscle-strengthening exercise and the associated factors: A systematic review consisting of 2,629,508 participants.

Purpose: The aim of this systematic review was to (1) estimate the prevalence of adhering to the MSE guidelines (at least 2 times/days a week) among adults; and (2) synthesize evidence on the correlates of adhering to the MSE guidelines. Methods: Five electronic databases were searched (March 2022), with a total of 30 observational studies consisting of 2,629,508 participants meeting the eligibility criteria. A meta-analysis was conducted to pool the prevalence of adhering to the MSE guidelines using the results of 21 eligible studies (study aim 1); and data reporting correlates of adhering to the MSE guidelines using 12 eligible studies were synthesized and categorized based on the Socioecological Model Framework (study aim 2). Results: Overall, 22.8 % (95%CI: 18.18 % ─ 27.77 %) of adults adhered to the MSE guidelines, and 23 potential correlates at five levels were examined. Five variables (i.e., sex, age, education level, socioeconomic status) at the sociodemographic level and two variables (i.e., body mass index, self-rated health) at the physical related level were identified as consistent correlates, but displaying weak to moderate association strengths. Conclusions: Less than a quarter of adults meet the MSE guidelines and multidimensional correlates are associated with the adherence to the guidelines, particularly sociodemographic correlates (e.g., sex, age, and educational level). Findings highlight the need to further promote the importance of engaging in MSE among adults and investing effective interventions that not only provide opportunities for MSE for adults, but also facilitate the development of skills and confidence to engage in MSE.

Association between walking speed and calcaneus stiffness index in older adults.

INTRODUCTION: The aim here is to examine the association between objectively measured usual walking speed (UWS) and bone status in community-dwelling older Chinese. MATERIALS AND METHODS: This is a cross-sectional study of a population of 1528 adults (817 females, mean age 68.5 ± 5.3; 711 males, mean age 69.1 ± 5.2) aged 60-79, living in communities in Shanghai. Walking speed was assessed using a 4-m walk test at a usual-pace walking speed a walking speed at which the subject felt relaxed-and bone status measured by quantitative ultrasound (QUS). The health-related characteristics of participants include family background, physical activity level, chronic disease, smoking and alcohol consumption, frequency of falls, vitamin intake, and hormone therapy. RESULTS: Multiple linear regression is used to analyses any association between UWS and bone status, adjusting for confounding factors showing a significant association between faster UWS and a higher calcaneal stiffness index (SI) (p < 0.01). Comparing the lowest quartile of the data set with the highest at UWS, a high SI is achieved with 5.34 (95% CI = 3.22, 7.46) (p < 0.01), after adjusting for confounders. An increase of 1 dm/s was associated with a 0.91 (95% CI = 0.53, 1.29) increase in SI. This relationship for most subgroups is consistent. CONCLUSION: Our findings suggest that UWS can be a sensitive indicator of calcaneal bone loss among an older population.

Double-function enhancement algorithm for low-illumination images based on retinex theory.

In order to solve the problems of noise amplification and excessive enhancement caused by low contrast and uneven illumination in the process of low-illumination image enhancement, a high-quality image enhancement algorithm is proposed in this paper. First, the total-variation model is used to obtain the smoothed V- and S-channel images, and the adaptive gamma transform is used to enhance the details of the smoothed V-channel image. Then, on this basis, the improved multi-scale retinex algorithms based on the logarithmic function and on the hyperbolic tangent function, respectively, are used to obtain different V-channel enhanced images, and the two images are fused according to the local intensity amplitude of the images. Finally, the three-dimensional gamma function is used to correct the fused image, and then adjust the image saturation. A lightness-order-error (LOE) approach is used to measure the naturalness of the enhanced image. The experimental results show that compared with other classical algorithms, the LOE value of the proposed algorithm can be reduced by 79.95% at most. Compared with other state-of-the-art algorithms, the LOE value can be reduced by 53.43% at most. Compared with some algorithms based on deep learning, the LOE value can be reduced by 52.13% at most. The algorithm proposed in this paper can effectively reduce image noise, retain image details, avoid excessive image enhancement, and obtain a better visual effect while ensuring the enhancement effect.

Analysis of national physical activity and sedentary behaviour policies in China.

PURPOSE: The aims of this study were to advance knowledge on physical activity (PA) and sedentary behaviour (SB) policies in China and to highlight related gaps and opportunities in the Chinese policy landscape. METHODS: Literature and web-based searches were performed to identify national PA and SB policies in China. We assessed which of the 17 elements of the Health-Enhancing Physical Activity Policy Audit Tool (HEPA PAT, version 2) are included in each of the policy documents and whether and how they address the 'cornerstones' of PA and SB policy: PA and SB guidelines, targets, surveillance and monitoring, and public education programmes. RESULTS: We found 60 national PA and SB policies, of which 54 focused on PA only and 6 focused on both PA and SB. There was a rapid increase in the number of policies issued between 2002 and 2021. In totality, the policies include all 17 key elements for a successful national policy approach to PA promotion according to the HEPA PAT. The policies reflect engagement from a range of sectors and encompass PA targets, recommendations for PA and SB, mandates and recommendations for school-related PA, plans for public education on PA, and plans for surveillance and monitoring of PA and SB. CONCLUSION: Our findings demonstrate that there has been increasing focus on PA and SB policies in China, which reflects efforts by policymakers to address the health burden of insufficient PA and excessive SB. More emphasis may be placed on SB in Chinese policy, particularly in terms of setting specific targets for population SB. Policymakers and other relevant public health stakeholders in China could also consider developing or adopting the 24-hour movement guidelines, in accordance with recent trends in several other countries. Collaboration and involvement of different sectors in the development and implementation of Chinese PA and SB policies should continue to be facilitated as part of a whole-of-system approach to health promotion.

24-Hour movement behaviours research during the COVID-19 pandemic: a systematic scoping review.

OBJECTIVES: Many studies examining 24-hour movement behaviours based on the 24-Hour Movement Guidelines (24HMG) have been published during the COVID-19 pandemic. However, no comprehensive reviews summarized and synthesized the evidence concerning studies using 24HMG. The aim of this scoping review was to synthesize the evidence from the 24HMG studies published during the pandemic. METHODS: Three electronic databases (Web of Science, PubMed, EBSCO) were utilized to conduct a literature search. The search procedure adhered to the guidelines set by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Initially, a total of 1339 research articles published in peer-reviewed journals were screened. After eliminating 461 duplicates, 878 articles remained. The titles and/or abstracts of these articles were then cross-checked, and 25 articles were included. Subsequently, two authors independently assessed full-text of articles based on the pre-defined inclusion and exclusion criteria, resulting in the final selection of 16 articles that met the inclusion criteria. Study characteristics (e.g., study population, study design, measurement) were extracted and then summarized. According to the Viable Integrative Research in Time-use Research (VIRTUE) epidemiology, the included studies were further classified into different but interrelated study domains (e.g., composition, determinants, health outcomes). RESULTS: The majority of included articles focused on children and adolescents as study population. This study primarily demonstrated that a low prevalence of meeting the 24HMG among children and adolescents during the COVID-19 pandemic. There has been a decline in the percentage of individuals meeting the 24HMG compared to the pre-COVID-19 period. The majority of included studies focused on sociodemographic factors when examining the correlates of meeting the 24HMG, while a few studies assessed factors of other domains, such as social, cultural, and environmental aspects. CONCLUSION: The COVID-19 pandemic had an impact on healthy 24-hour movement behaviours in children and adolescents. In conjunction with the studies conducted during the COVID-19 pandemic, more studies were encouraged to explore the correlates of meeting the 24HMG and the associated health benefits in wider ranges of populations.

Efficient dynamic control method of light polarization using single phase-only liquid crystal on silicon spatial light modulators for optical data storage.

The technology of five-dimensional (5D) optical data storage in transparent materials paves a promising way to unlimited lifetime data storage for future cloud use. Phase-only liquid-crystal-on-silicon spatial light modulators (LCOS SLMs) have already exhibited its potential for this application in tailoring ultrafast laser writing beams for 5D optical data storage. A phase-only LCOS SLM can generate arbitrary data patterns by using diffractive holographic imaging for data writing light beam generation. However, the polarization control of the output holographic image is still achieved by using an external polarization modulator, which leads to complications, bulkiness, and large delays in current methods. In this paper, we presented an efficient phase and polarization modulation method through a compact system based on a single phase-only LCOS SLM to simultaneously control both the holographic image and its polarization state. The proposed method utilizes two-polarization-component coding in conjunction with a polarization component rotation technique in a compact system. Using this polarization rotation technique, two light components can be independently coded by separately using two holograms on two halves of the LCOS SLM. We experimentally construct a proof-of-concept prototype of the compact system, and the effectiveness of the system has been experimentally verified.

Associations of physical activity with academic achievement and academic burden in Chinese children and adolescents: do gender and school grade matter?

BACKGROUND: Physical activity (PA) was significantly associated with cognition and mental health in children and adolescent. However, there were few studies examining the associations of PA with academic achievement (AA) and academic burden (AB) by gender and school grade. Hence, this study aimed to 1) investigate the associations of moderate-to-vigorous PA (MVPA) with AA and AB in Chinese children and adolescents, and 2) assess whether these associations vary by gender and school grade. METHODS: Using a multi-stage stratified cluster sampling design (at four different regions in Southern east China), 2653 children and adolescents (8-19 years old, 51.2% girls) were included. A self-reported questionnaire was used to collect data on study participants' gender, school grade, family social economic status (SES), parental education level, MVPA, AA and AB. Binary logistic regression was applied to examine the associations of MVPA with AA (groups: above-average AA, average and below-average AA) and AB (groups: reporting AB, reporting no AB) with odds ratios (ORs) and 95% confidence intervals (CIs). After testing gender*grade interaction, those associations were explored by gender and school grade separately. RESULTS: In the overall sample, compared with children and adolescents who did not meet the PA guidelines (at least 60 min MVPA daily), children and adolescents who met the PA guidelines were more likely to have above-average (OR = 1.61, 95% CI: 1.21-2.11) AA, and report no AB (OR = 1.61, 95% CI: 1.13-2.30). In both genders, meeting the PA guidelines was positively associated with above-average AA (OR = 1.43, 95% CI: 1.01-2.03 for boys; OR = 2.22, 95% CI: 1.43-3.44 for girls). However, the significant relationship between meeting the PA guidelines and AB was observed only in girls (OR = 1.99, 95% CI: 1.17-3.39). Meeting the PA guidelines was positively associated with above-average AA (OR = 1.68, 95% CI: 1.18-2.40), and reporting no AB (OR = 1.77, 95% CI: 1.08-2.91) only in middle school students. CONCLUSIONS: This study suggested that sufficient PA may be a contributary factor of improved AA and lower level of AB in Chinese children and adolescents. However, associations of PA with AA and AB may be different across gender or school grade. Promoting PA among girls or middle school students may be a good approach to improve AA and reduce AB.

Do the dual-task "8-foot up and go" tests provide additional predictive value for early detection of cognitive decline in community-dwelling older women?

BACKGROUND: The 8-Foot Up and Go (8UG) test is a widely used mobility assessment. Some dual-task mobility assessments have been developed to help detect cognitive decline. AIMS: This study developed a dual-task version of 8UG test to investigate the dual-task 8UG performance and to evaluate the ability of dual-task 8UG test in detecting cognitive decline. METHODS: A total of 101 eligible community-dwelling women aged 60-74 years were grouped into the mild cognitive impairment group (MCI, n = 49) and the non-cognitive impairment group (NCI, n = 52). The 8UG tests under single-task (ST), manual dual-task (MT), and cognitive dual-task (CT) conditions were performed respectively. The dual-task cost (DTC) and the correct response rate (CRR) were calculated to quantify the dual-task interference. RESULTS: Participants spent more time in performing the 8UG test under dual-task conditions. No differences were observed between NCI and MCI groups for 8UG parameters under ST and MT conditions (p > 0.05). When executing CT, significant differences were found in the number of correct answers and CRR (p < 0.05). CRR showed the strongest ability to predict MCI with a cut-off point of 0.50 (71.2% sensitivity and 61.2% specificity). DISCUSSION: Both manual and cognitive dual-task were found to interfere with the 8UG performance. CRR with cutoff point of 0.50 could be a potential predictor of MCI in community-dwelling older women. CONCLUSIONS: The CRR of the cognitive dual-task 8UG test could be recommended as a potential predictor for the early detection of MCI in community-dwelling older women.

Dynamic Phase and Polarization Modulation Using Two-Beam Parallel Coding for Optical Storage in Transparent Materials.

In this paper, we propose and experimentally demonstrate a parallel coding and two-beam combining approach for the simultaneous implementation of dynamically generating holographic patterns at their arbitrary linear polarization states. Two orthogonal input beams are parallelly and independently encoded with the same target image information but there is different amplitude information by using two-phase computer-generated holograms (CGH) on two Liquid-Crystal-on-Silicon-Spatial-Light Modulators (LCOS SLMs). Two modulated beams are then considered as two polarization components and are spatially superposed to form the target polarization state. The final linear vector beam is created by the spatial superposition of the two base beams, capable of controlling the vector angle through the phase depth of the phase-only CGHs. Meanwhile, the combined holographic patterns can be freely encoded by the holograms of two vector components. Thus, this allows us to tailor the optical fields endowed with arbitrary holographic patterns and the linear polarization states at the same time. This method provides a more promising approach for laser data writing generation systems in the next-generation optical data storage technology in transparent materials.

Associations between various kinds of parental support and physical activity among children and adolescents in Shanghai, China: gender and age differences.

BACKGROUND: The associations between various kinds of parental support and children and adolescents' physical activity (PA) are inconclusive. This study aimed 1) to examine the associations between various kinds of parental support and children and adolescents' moderate-to-vigorous physical activity (MVPA), and 2) to examine gender and age differences in the association between each specific kind of parental support and MVPA. METHODS: Using a multi-stage stratified and random cluster sampling method, 711 schools in Shanghai were selected (data were collected from October 2014 to February 2015). In total, 61,429 school-aged children (6-18 years old, 50.7% boys) and their parents were included. Self-reported questionnaires were used to measure sociodemographic characteristics, MVPA and various kinds of parental support, including parental encouragement (PAEN), parental involvement (PAIV), parental financial support (PAFS) and, parental modeling (PAMD). Descriptive statistics and Chi-square were used to report the level of MVPA and its difference across various kinds of parental support by gender groups. The logistic regression analysis was used to examine the associations between parental support and MVPA with odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: Overall, 19.4% of children and adolescents accumulated MVPA at least 60 min/day. Boys were more physically active than girls (21.4% > 17.4%, p <  0.001). According to the observation of OR estimates, girls may be more susceptible to the influences from various kinds of parental support than boys (OR = 1.59, 1.61, 1.27 and 1.63, 95% CI: 1.19-1.73 among girls, and OR = 1.48, 1.60, 1.21, and 1.60, 95% CI: 1.14-1.69 among boys for PAEN, PAIV, PAFS and PAMD respectively). PAMD is the only one supportive kind that was positively associated with MVPA in both genders across all grades (OR = 1.29-2.98, 95% CI: 1.09-4.08 among boys; OR = 1.27-2.64, 95% CI: 1.10-4.10 among girls). CONCLUSIONS: Less than one fifth of children and adolescents accumulated 60 min MVPA per day. Various kinds of parental support have important effects on children and adolescents' MVPA, which varied by gender and grades. PAMD, in particular, should be emphasized more than PAEN, PAIV and PAFS in family-based interventions aiming at increasing PA in the future.

Co-existence of physical activity and sedentary behavior among children and adolescents in Shanghai, China: do gender and age matter?

BACKGROUND: There is limited evidence for the prevalence of the co-existence of physical activity (PA) and sedentary behavior (SED), and its correlates among children and adolescents. This study has two aims: 1) to investigate the prevalence of PA and SED, and their co-existence, and 2) to examine the associations between PA or SED, or both with gender and age among children and adolescents in Shanghai, China. METHODS: Using a cross-sectional study design (conducted from September to December 2014), 50,090 children and adolescents (10-18 years old, 50.4% boys) were included in this study. A self-reporting questionnaire was used to measure participants' sociodemographic characteristics, PA, and SED. Descriptive statistics were used to describe sample characteristics, the prevalence of PA and SED, and their co-existence. A Generalized Linear Model was conducted to explore the associations between the prevalence of PA and SED, and their co-existence with gender and age separately. RESULTS: Of the children and adolescents studied, only 18.4% met the guidelines for PA, 25.5% met the guidelines for SED, and 5.7% met the guidelines for both. Boys were more physically active (aOR = 1.43, 95% CI: 1.36-1.50), and girls were less sedentary (aOR = 1.29, 95%CI: 1.24-1.34). The prevalence of PA, SED, or both all declined as age increased (p < 0.001). Stratified analysis by gender revealed greater declining trends of meeting the PA or SED guidelines, or both in girls (all p < 0.005). CONCLUSION: Very few children and adolescents showed active lifestyles, and this was significantly related to age. Effective interventions aiming to promote PA and concurrently to limited SED among children and adolescents should be implemented as early as possible.

Associations between socioeconomic status and screen time among children and adolescents in China: A cross-sectional study.

BACKGROUND: Socioeconomic status (SES) is an important determinant of screen time (ST) in children and adolescents, however, the association between SES and ST is not fully understood in China. This study aimed to investigate the association between SES and ST (operationalized as meeting the ST guidelines; no more than 2 hours per day) in Chinese children and adolescents. METHODS: Cross-sectional data of 2,955 Chinese children and adolescents aged 8 to 17(53.4% girls) were used. SES was measured using indicators of parental education and perceived family wealth. ST was assessed with detailed items from the Health Behaviour School-aged Children survey questionnaires. Descriptive statistics and a Chi-square test were used to report the sample characteristics and analyse ST differences across different sociodemographic groups. A binary logistic regression was then applied to analyse the association of SES indicators with ST in children and adolescents. RESULTS: Overall, 25.3% of children and adolescents met the ST guidelines. Children and adolescents with higher parental education levels were 1.84 [95% CI 1.31-2.57; father] and 1.42 [95% CI 1.02-1.98; mother] times more likely to meet the ST guidelines than those with lower parental education levels. Associations between SES and ST varied across sex and grade groups. Moreover, the associations of SES with ST on weekdays and weekends were different. CONCLUSIONS: This study demonstrated the association between SES and ST in children and adolescents, highlighting the importance of targeting children and adolescents with low SES levels as an intervention priority. Based on our findings, specific interventions can be tailored to effectively reduce ST. Future studies are encouraged to use longitudinal or interventional designs to further determine the association between SES and ST.

Correlates of Meeting the Muscle-Strengthening Exercise Guidelines in Children and Adolescent.

This study aimed to explore the potential correlates of muscle-strengthening exercise (MSE) in Chinese children and adolescents. A convenient sample (n = 3733) was recruited into this study. Self-reported questionnaires were used to collect information on sex, grade, ethnicity, residence, family composition, moderate to vigorous physical activity (MVPA), family income, parent's education level and MSE in children and adolescents as well as their parent(s). The prevalence of meeting the MSE guidelines was 62.1%. Children and adolescents who were in primary or middle school were more likely to meet the MSE guidelines ([primary school] OR = 2.33, 95% CI: 1.16-4.68; [middle school] OR = 4.62, 95% CI: 2.27-9.39). Children and adolescents with Han ethnicity had a higher likelihood to meet the MSE guidelines (OR = 1.97, 95% CI: 1.37-2.83). Children and adolescents meeting the MVPA recommendation were more likely to meet the MSE guidelines (OR = 5.41, 95% CI: 3.97-7.37). Relative to those who had a parent not meeting the MSE guidelines, those with either father or mother meeting the MSE guidelines were more likely to meet the MSE guidelines (OR = 1.32, 95% CI: 1.13-1.55). Our study may offer evidence for future MSE interventions in Chinese children and adolescents.

Associations of sport participation, muscle-strengthening exercise and active commuting with self-reported physical fitness in school-aged children.

Background: Numerous studies suggest a positive association between physical activity and physical fitness in schoolchildren. However, little is known about some neglected forms of physical activity and their associations with physical fitness. This study was conducted via a self-reported questionnaire, owing to the COVID-19 pandemic in many regions in China. Purpose: This study explores the associations between participating in sports, muscle-strengthening exercises, and active commuting with self-reported physical fitness assessed by the International Fitness Scale (IFIS). Methods: A total of 3,807 study participants (ages 11-17) from 12 public schools in South-eastern China were recruited, with 2,407 providing valid data on variables for analysis. Study participants were asked to self-report their sociodemographic factors (i.e., sex, grade, age), participation in sports (never, 1-3 times per month, 1-2 times per week, and 3 or more times per week), muscle-strengthening exercise (0-7 days) and active commuting (0-5 days). Generalized linear models were used to explore the associations between sports participation, muscle-strengthening exercise, and active commuting with self-reported physical fitness (comprising general physical fitness, cardiorespiratory fitness, muscular strength, speed and agility, and flexibility). A total of 2,407 children and adolescents with a mean age of 13.82 (±2.1) years were included in the study's final analysis. Results: The study found no significant association between active commuting and physical fitness. Regarding participating in sports and muscle-strengthening exercises, positive, significant associations were found, which showed that a higher frequency of participating in sports and more participation in muscle-strengthening exercises are associated with improved physical fitness. Conclusion: This study offered evidence on the roles of some aspects of physical activity in physical fitness. To promote health in children and adolescents, they should be encouraged to participate in more sports and engage in muscle-strengthening exercises.

Associations between socioeconomic status and physical activity: A cross-sectional analysis of Chinese children and adolescents.

Objectives: Although socioeconomic status (SES) has been shown to be an important determinant of physical activity (PA) in adults, the association in children and adolescents remains less consistent based on evidence from western developed countries. The purpose of this study, therefore, is to investigate associations between SES and PA among Chinese children and adolescents. Methods: A cross-sectional study was conducted with a self-reported questionnaire in China. The multi-stage stratified cluster sampling method was used, and 2,955 children and adolescents (8-17 years old, 53.4% girls) were enrolled in this study. SES was assessed by measuring parental education levels, perceived family wealth, and Family Affluence Scale II (FAS II). PA was assessed by reliable and valid items from the Health Behavior School-aged Children Surveillance questionnaires. Descriptive statistics were used to report sample characteristics, including demographic characteristics, levels of PA, and SES. The Chi-square test was applied to analyze the differences of PA in gender and school period. Binary logistic regression was used to analyze the association between SES and PA among children and adolescents. Results: Overall, 10.4% of children and adolescents accumulated moderate-to-vigorous physical activity (MVPA) at least 60 min per day. Boys were more physically active than girls (14.1% vs. 7.2%, p < 0.001). Higher socioeconomic status was positively associated with higher physical activity levels among children and adolescents, especially using FAS and mother education level as SES measures. The association between SES and PA varied by gender and grade group, and the effects of SES are also different on weekdays and weekends. Conclusion: This study found socioeconomic disparities in PA among Chinese children and adolescents, and showed the importance of targeting children and adolescents with low SES intervention priority. Based on these research findings, it is suggested that SES, especially for FAS and mother education level, should be considered when designing and implementing the promotion of regular PA in children and adolescents. Health policymakers may use this information to develop interventions to reduce health inequalities among children and adolescents in the future.

Is the Health Behavior in School-Aged Survey Questionnaire Reliable and Valid in Assessing Physical Activity and Sedentary Behavior in Young Populations? A Systematic Review.

Backgrounds: Using the self-reported questionnaire to assess the levels of physical activity (PA) and sedentary behavior (SB) has been a widely recognized method in public health and epidemiology research fields. The selected items of the Health Behavior in School-aged (HBSC) Survey Questionnaire have been used globally for measurements and assessments in PA and SB of children and adolescents. However, there are no comprehensive and critical reviews to assess the quality of studies on reliability and validity of selected items for PA and SB measurement and assessment derived from the HBSC. Thus, this review aimed to critically assess the quality of those studies and summary evidence for future recommendations. Methods: A systematic review protocol was used to search potentially eligible studies on assessing reliability and validity of PA and SB measures of the HBSC questionnaire. electronically academic databases were used. The information on the reliability and validity of the PA and SB measures were extracted and evaluated with well-recognized criteria or assessment tools. Results: After a literature search, six studies were included in this review. The reliability of PA measures of the HBSC questionnaire showed a moderate agreement while the reliability of SB measures showed a great variation across the different items in the different subgroups. The validity of the PA measures had acceptable performance, whereas no studies assess the validity of the SB measures. The included studies all had quality weaknesses on reliability or validity analysis. Conclusions: The PA and SB measures of the HBSC questionnaires were reliable in assessing PA and SB among adolescents. However, a little evidence showed that PA measures are partially valid in assessing PA, but no evidence confirmed the validity of SB measures. The included studies all had methodological weaknesses in examining the reliability and validity of the PA and SB measures, which should be addressed in the future. Further studies are encouraged to use a more standardized study design to examine the reliability and validity of the PA and SB measures in more young populations.

Move More, Sit Less and Sleep Well: An analysis of WHO movement guidelines for children under 5 years of age.

Insufficient physical activity (PA), prolonged sedentary behavior (SB) and inadequate sleep (SLP) are detrimental factors to population health. To address health issues caused by insufficient PA, excessive SB and poor SLP, the World Health Organization (WHO) updated PA and SB guidelines for all populations aged from 5 years to 65 years and older in 2020. For children under 5 years old, the WHO issued the first global guidelines for PA, SB and SLP (collectively refer to movement behaviors) in April 2019. The guidelines applied a holistic approach to promote health behaviors, filling the gap of no comprehensive global movement guidelines for young children. Although the guidelines for young children offer guidance for health promotion, some research and practice implications and other issues should be mentioned. This commentary includes considerations for the importance of the WHO guidelines for younger children, critical analysis of evidence for developing the guidelines, and recommendations for future research and practice. The aim of this paper is to further advance health research in younger populations.

Association between physical education classes and physical activity among 187,386 adolescents aged 13-17 years from 50 low- and middle-income countries.

OBJECTIVE: This study aimed to examine the association between physical education classes and PA among adolescents from 50 low- and middle-income countries (LMICs). METHODS: A self-reported questionnaire from the Global School-based Student Survey (GSHS) was used to collect information on participation frequency of physical education classes and being physically active over the last week, as well as other control variables (e.g., sex, age, country, sedentary behavior). Multivariable logistic regression and a pooled meta-analysis were performed to explore the association and compared country-wise differences. RESULTS: Included adolescents aged from 13 to 17 years (n=187,386, %boys=51.7; mean age=14.6 years), the prevalence of sufficient PA (meeting the PA guidelines) was 14.9%. The prevalence of 5 days or more to engage in physical education classes was 16.5%. Compared with adolescents who had 0 days for physical education classes, higher participation frequency was more likely related to sufficient PA (OR: 1 day=1.34, 2 days=1.66, 3 days=1.67, 4 days=1.79, 5 days or more=2.46), these findings were also observed in both sexes. A moderate inconsistency on the association across the included countries was found (I2=53%, p<0.01), although the pooled OR was 1.50 (95% CI: 1.36-1.65). CONCLUSIONS: Participating in more physical education classes may be an effective approach to increase physical activity levels among adolescents in LMICs. However, promoting physical activity levels among adolescents in LMICs through physical education classes should consider more country-specific factors.

Meeting 24-h movement guidelines: Prevalence, correlates, and the relationships with overweight and obesity among Chinese children and adolescents.

BACKGROUND: Meeting 24-h movement guidelines by children and adolescents has been associated with improved indicators of health, although it has been under-studied in China. Hence, this study aimed to investigate the prevalence of meeting the 24-h movement guidelines, its correlates, and its relationships with body mass index in children and adolescents in China. METHODS: Cross-sectional data from the 2017 Youth Study in China of 114,072 children and adolescents (mean age = 13.75 years, 49.18% boys) were used. Meeting 24-h movement guidelines (≥60 min of daily moderate-to-vigorous physical activity, ≤2 h of daily leisure screen time, 9-11 h and 8-10 h nightly sleep duration for 6-13-year-olds and 14-17-year-olds, respectively) and height and weight of all participants were assessed. The prevalence of meeting the 24-h movement guidelines and World Health Organization weight status categories were determined. Generalized linear models were used to determine the correlates of meeting the 24-h movement guidelines and the relationships of meeting the 24-h movement guidelines with overweight (OW) and obesity (OB). RESULTS: Only 5.12% of Chinese children and adolescents met the 24-h movement guidelines, and 22.44% were classified as OW/OB. Older children and adolescents were less likely to meet the 24-h movement guidelines. Parental education level and family income were positively related to meeting the 24-h movement guidelines. Children and adolescents meeting the 24-h movement guidelines showed lower odds ratios for OW/OB. Compared with participants meeting the 24-h movement guidelines, boys in 4th-6th grades met none of the recommendations (OR = 1.22, 95%CI: 1.06-1.40), met the screen time recommendation only (OR = 1.13, 95%CI: 1.01-1.28), met the nightly sleep duration recommendation only (OR = 1.14, 95%CI: 1.03-1.28), and had significantly higher odds ratios for OW/OB. Similar trends were observed for girls in 4th-6th grades: meeting none of the guidelines (OR = 1.35, 95%CI: 1.14-1.59), meeting sleep duration guidelines only (OR = 1.23, 95%CI: 1.08-1.39), and meeting moderate-to-vigorous physical activity + nightly sleep duration guidelines (OR = 1.24, 95%CI: 1.01-1.54). For girls in 7th-9th grades, the following trend was observed: meeting none of the guidelines (OR = 1.30, 95%CI: 1.01-1.67). CONCLUSION: Very few Chinese children and adolescents met the 24-h movement guidelines. Age (negatively correlated), parental education level, and family income (both positively correlated) were correlates of meeting the 24-h movement guidelines. Children and adolescents meeting the 24-h movement guidelines were more likely to have lower risks for OW/OB, especially in the youngest age group (Grades 4-6); and girls in the middle age group (Grades 7-9) were also more likely to have lower risks for OW/OB. Further research studies should explore additional correlates and determinants for meeting the 24-h movement guidelines. Also, future studies should use longitudinal or interventional designs to determine the relationships between meeting the 24-h movement guidelines and OW/OB and other health indicators, while taking sex and age differences into account.

Prevalence of Physical Activity and Sedentary Behavior among Chinese Children and Adolescents: Variations, Gaps, and Recommendations.

Physical-activity (PA) and sedentary-behavior (SB) assessment is of particular importance in the promotion of health in young people. However, there is no comprehensive overview of PA and SB from national surveys among Chinese children and adolescents. Following a literature search for Chinese national health surveys, 11 papers from six national surveys were found. Of the included studies, the majority applied self-reported questionnaires to estimate the prevalence of PA and SB. Owing to different definitions of the prevalence of PA and SB and various measures, a large variation in prevalence of PA and SB was observed. Such variations were attributable to methodological and practical issues. This study highlights the current gaps in estimating the national prevalence of PA and SB among Chinese children and adolescents, which should be addressed. To improve the quality of PA and SB surveillance, standardized measurement protocols to estimate the prevalence of PA and SB more accurately among Chinese children and adolescents are urgently required.