Forced vital capacity and body mass index of Xinjiang children and adolescents: an analysis based on seven successive national surveys, 1985-2014.

BACKGROUND: Pulmonary function is very important for the healthy development of children and adolescents. However, fewer studies have been conducted on pulmonary function trends in children and adolescents in remote areas. The aim of this study was to estimate the forced vital capacity (FVC) trend and its relationship with body mass index (BMI) among young people in Xinjiang during 1985-2014 using data from seven successive national surveys. METHODS: A total of 19,449 Xinjiang children and adolescents aged 7-18 years were extracted from the Chinese National Survey on Students' Constitution and Health. Height, weight, and FVC were measured repeatedly in each survey. FVC comparisons between adjacent surveys by age and sex were conducted by nonparametric Kruskal-Wallis after Kolmogorov-Smirnov of normality. One-way ANOVA and least significant difference(LSD) method was used to compare differences in FVC levels of Xinjiang children and adolescents with different BMI. The relationship between BMI and FVC was investigated using a nonlinear regression model. RESULTS: The FVC levels of Xinjiang children and adolescents peaked in 2000, with overall FVC levels being 8.7% higher in 2000 than in 1985. Since then, a substantial decline occurred, contrasting to 2000, with FVC levels decreasing by 27% in 2014, which was still lower than that in 1985 by 20.73%. The proportion of overnutrition boys increased from 0.2% in 1985 to 22.1% in 2014, and girls from 0.5% in 1985 to 14.5% in 2014. An inverted U-shape association between FVC and BMI values was obtained for Xinjiang children and adolescents. CONCLUSIONS: Targeted measures should be carried out in schools to control BMI levels to ensure good lung function in children and adolescents in Xinjiang. Future studies should pay more attention to other factors affecting FVC, such as dietary behaviour, physical activity, and racial differences among children and adolescents.

Regional variation in growth status: A cross-sectional survey among Tibetan adolescents living at three different high altitudes in Tibet, China.

OBJECTIVE: To explore the regional and age variation in growth status and age-by-site interaction effect on the growth status among Chinese Tibetan adolescents at different altitudes in Tibet, China. METHODS: The research was conducted in three regions of Tibet, China: Nyingchi (average altitude 3100 m), Lhasa (average altitude 3650 m), and Nagqu (average altitude 4500 m). A total of 3817 Chinese Tibetan adolescents aged 12-18 years were tested for height, weight, chest circumference, and waist circumference. One-way ANOVA was used to compare the growth status of Chinese Tibetan adolescents. Two-way ANOVA was used to explore the age-by-site interaction effect on the growth status of Chinese Tibetan adolescents. RESULTS: The height, weight, and chest circumference of Chinese Tibetan adolescents in Nagqu are the lowest among the three cities. Age and site have an interaction effect influence on the growth status of Chinese Tibetan adolescents (p < .01). CONCLUSIONS: The growth indicators (height, weight, chest circumference, WC) of Chinese Tibetan adolescents differed with altitudes. Policies to improve the growth status of Chinese Tibetan adolescents in Nagqu are urgently needed.

Roles of age, sex, and weight status in the muscular fitness of Chinese Tibetan children and adolescents living at altitudes over 3600 m: A cross-sectional study.

OBJECTIVE: This study aimed to assess the role of age, sex, and weight status in the development of muscular fitness in a large sample of Chinese Tibetan children and adolescents aged 7-18 years living in areas over 3600 m. METHOD: A sample of 4673 Chinese Tibetan children and adolescents aged 7-18 years were recruited from 21 schools in three cities (Lhasa, Naqu, and Anduo) of Tibet, China. Grip strength, standing long jump, 30-s sit-ups, and 50-m dash were conducted to determine muscular fitness. Independent sample t tests were conducted to compare muscular fitness between boys and girls for each age group. The changes in mean scores on each muscular fitness test were estimated. The influence of weight status on muscular strength level was also estimated using one-way ANOVA and LSD tests. We also compared the average muscular fitness between Chinese Tibetan and Chinese average level. RESULTS: The muscular fitness of Chinese Tibetan boys aged 7-18 years was higher than that of girls, with older children outperforming younger children. Among the Chinese Tibetan boys, those in the normal-weight group showed the best performance, whereas overweight group showed the best performance among the girls. The performance of Chinese Tibetan children and adolescents in standing long jump and 50-m dash was lower while that in sit-ups was higher than the performance of their Chinese counterparts. CONCLUSION: Chinese Tibetan children and adolescents have relatively strong abdominal strength, but lower limb strength, which needs to be improved. Age, sex, and weight status should be considered when designing interventions to improve muscular fitness.

Compared with dietary behavior and physical activity risk, sedentary behavior risk is an important factor in overweight and obesity: evidence from a study of children and adolescents aged 13-18 years in Xinjiang, China.

BACKGROUND: Malnutrition or insufficient physical activity (PA) is a risk factor for obesity and chronic disease in children and adolescents. Affected by different economic circumstance, ethnic, dietary behavior, physical activity and other factors, children and adolescents in Xinjiang, China are facing a severe situation of overweight and obesity prevention and control. It is necessary to analyze the dietary behavior and physical activity of children and adolescents with different nutritional status and the relationship between them. METHODS: Using a stratified cluster sampling method in Xinjiang, China, 4833 middle school students aged 13-18 were selected., and tests for height and weight were conducted. Self-assessment questionnaires were completed for Dietary Behaviors, Physical Activity, and Sedentary Behaviors as well. Chi-square test, Logistic regression analysis and other methods were used to analyze the relationship between Dietary Behaviors, Physical Activity, Sedentary Behaviors and other health behavior risk factors and Weight and BMI. RESULTS: Children and adolescents aged 13-18 in Xinjiang, China, girls had a lower BMI compared with boys(19.49 VS. 20.41). The proportions of Underweight, Overweight and Obese among girls were lower (Underweight: 11.8 VS. 14.5; Overweight: 7.6 VS. 12.7; Obese 2.3 VS. 7.0).Boys with higher risk of sedentary had a 1.46-fold higher risk of developing Overweight/Obese than those with lower risk of sedentary (95%CI: 1.07-2.01).Girls with higher risky diet had a 1.56-fold higher risk of developing Underweight than those with lower risky diet (95%CI: 1.11-2.19). For all participants, the risk of Overweight/Obese in children and adolescents with higher risk of sedentary was 1.45 times more than that of children and adolescents with lower Risk sedentary (95%CI: 1.12 ~ 1.88). Overall, Weight had a significant correlation with PA risk (r = 0.076, P < 0.01) and sedentary behavior risk (r = 0.035, P < 0.05). BMI had a key correlation with PA risk (r = 0.064, P < 0.01) and sedentary behavior risk (r = 0.037, P < 0.05). CONCLUSIONS: The detection rate of Underweight among children and adolescents aged 13-18 in Xinjiang, China is higher, while the detection rate of Overweight and Obese is lower than that of the whole country. Static behavior was an important factor affecting the occurrence of Overweight and Obese in children and adolescents, and the performance of boys was more obvious than that of girls.The results further improve the data on the weight status of Chinese children and adolescents and their influencing factors, and call on Chinese society and schools to continue their efforts to prevent and reduce malnutrition and obesity among children and adolescents in Xinjiang.

Relationship between waist circumference and cardiorespiratory fitness in Chinese children and adolescents: Results from a cross-sectional survey.

BACKGROUND: This article assessed the relationship between waist circumference (WC) and cardiorespiratory fitness (CRF) of children and adolescents aged 7-18 years. METHODS: Using a stratified cluster random sampling method, 92,574 children and adolescents (47,364 males and 45,210 females) were extracted. CRF was measured by performance in the 20 m shuttle run test (20mSRT) and the subsequent estimation of maximal oxygen consumption ( V ˙ O2max) using the Léger equations. Participants were divided into five groups of WC percentiles and three groups of CRF percentiles by the Lambda Mu Sigma (LMS). The correlation between WC and CRF was examined by one-way ANOVA and curvilinear regression analysis. RESULTS: WC increased with age, while V ˙ O2max showed an age-related decline. Controlling for gender, urban, and rural factors, for children and adolescents aged 10-12, 13-15, and 16-18 years, the V ˙ O2max Z-score of the normal WC group was significantly higher than the very low WC group (P < 0.05). Controlling for gender, urban, and rural factors, for participants aged 7-18 years, the V ˙ O2max Z-score of the normal WC group was significantly higher than the high WC group and the very high WC group (P < 0.05). CONCLUSIONS: It generally shows a "parabolic" trend between WC-Z and V ˙ O2max-Z. The CRF among children and adolescents in the normal WC group is significantly higher than that in the low and the high WC groups.

Relationship between cardiorespiratory fitness and latitude in children and adolescents: Results from a cross-sectional survey in China.

BACKGROUND: This study assessed the correlation between latitude and the cardiorespiratory fitness (CRF) of children and adolescents. METHODS: In 16 provinces and autonomous regions in China, 25,941 children and adolescents aged 10-18 were included. CRF was measured using the 20 m shuttle run test (20 m SRT) and estimated peak oxygen uptake (VO2peak). One-way ANOVA and multiple regression analysis were used to explore the correlation between CRF and latitude in children and adolescents. RESULTS: The VO2peak values of the low (south), middle, and high (north) latitude groups for boys were 43.1, 43.1, and 40.7 mL/kg/min, respectively, and 40.0, 40.0, and 38.5 mL/kg/min for girls, respectively. After adjusting for confounding factors, the regression coefficients (ß) between VO2peak-Z and both latitude-Z and (latitude-Z)2 for boys were -0.151 and -0.043, respectively. For girls, they were -0.142 and -0.020, respectively. The Partial correlation coefficient (r) for latitude-Z and (latitude-Z)2 were -0.14 and -0.04 for boys, and -0.13 and -0.02 for girls, respectively. CONCLUSION: The CRF among children and adolescents in high latitude regions is significantly lower than that in middle and low latitude region, and it generally shows a "parabolic" trend between Latitude-Z and VO2peak-Z.

The sex-based disparity in BMI-for-age z-score trends among Xinjiang children and adolescents using four rounds of cross-sectional surveys from 1985 to 2014.

BACKGROUND: This study aimed to evaluate trends in body mass index (BMI)-for-age z-scores among children and adolescents in Xinjiang. METHODS: Data were obtained for children and adolescents aged 7-18 years in Xinjiang from the Chinese National Survey on Students' Constitution and Health (CNSSCH) in 1985 (n = 14 683), 1995 (n = 7198), 2005 (n = 10 253) and 2014 (n = 18 521). RESULTS: The BMI-for-age z-score distribution of children and adolescents in Xinjiang showed an increased mean BMI-for-age z-score, dispersion and right-skewed of BMI-values, with a rapid increase in BMI with increasing BMI percentiles. The sex-based disparity in BMI-for-age z-scores became wider in the past 30 years. CONCLUSIONS: Sex-based targeted public health measures and policies are urgently needed in Xinjiang. The rapid increases in the upper percentiles also implicated further efforts to prevent weight gain in those living already with overweight or obesity.

Psychological symptoms are associated with screen and exercise time: a cross-sectional study of Chinese adolescents.

BACKGROUND: Mental disorders among adolescents have become a worldwide public health problem. This study aimed to estimate the best combination of exercise time and screen time to promote the mental health of Chinese adolescents. METHODS: Participants included 7200 Chinese adolescents aged 13-18 years from six regions of China. Screen and exercise time data were collected via a self-rated questionnaire. Psychological symptoms (e.g., often feeling depressed, school-weary) were evaluated with the "Multidimensional Sub-health Questionnaire of Adolescents". Chi-squared tests and logistic regression analysis were conducted to investigate the differences in and correlations among screen time, exercise time, and psychological symptoms. RESULTS: The overall detection rate of psychological symptoms among Chinese adolescents was 21.4% (22.1% for boys and 20.6% for girls). Psychological symptom detection rates were lowest among adolescents with 1-2 h/d of screen time (19.5%) and those with 30-60 min/d of exercise time (17.3%). Screen time > 2 h/d (OR = 1.38, P < 0.001) and exercise time < 30 min/d (OR = 1.62, P < 0.001) were positively correlated with psychological symptoms. CONCLUSION: Screen and exercise time are associated with psychological symptoms in Chinese adolescents. A combination of 1-2 h/d of screen time and 30-60 min/d of exercise time is provided as a reference for better mental health.

Comparison of growth and nutritional status of Chinese and Japanese children and adolescents.

BACKGROUND: The difference in growth and nutritional status, both important indices of population quality, between Chinese and Japanese children and adolescents is unknown. AIM: This study aimed to compare growth and nutritional status between Chinese and Japanese children and adolescents. SUBJECTS AND METHODS: The height-for-age and BMI-for-age distribution of 9,226 children and adolescents aged 7-18 years from China and Japan were described with the Lambda Mu and Sigma method. Wasting, overweight and obesity were evaluated based on BMI-for-age cut-offs of the 2007 WHO Child Growth Reference. RESULTS: For boys, the overall average height, weight and BMI of Chinese participants were 3.0 cm, 4.8 kg and 1.2 kg/m2 greater compared with Japanese participants, respectively; for girls, these were 4.6 cm, 3.9 kg and 0.6 kg/m2, respectively. Compared with Japanese children, the 3rd, 50th and 97th percentiles of height-for-age, 1Z-score, and 2Z-score of BMI-for-age of Chinese children were greater, whereas the minus 2Z-scores of Chinese children were less. The prevalence of wasting, overweight and obesity among Chinese participants was greater. CONCLUSIONS: Compared with Japanese children, Chinese children tended to be taller. The worrying burden of overweight, obesity and wasting was recognised among Chinese children.

Normative Reference Values and International Comparisons for the 20-Metre Shuttle Run Test: Analysis of 69,960 Test Results among Chinese Children and Youth.

There is increasing evidence that cardiorespiratory endurance (CRE) is declining among Chinese children and youth. The 20-meter shuttle run test (20-m SRT) is considered the most effective and widely used field-based measurement of CRE for children and youth worldwide. However, there have been few attempts to set 20-m SRT norms for Chinese children and youth. We aimed to develop sex- and age-specific 20-m SRT norms for Chinese children and youth, and compare them with international standards. Participants were 69,960 healthy children and youth aged 9-17 years from six geographical areas of China, selected using a stratified cluster random sampling method. Sex- and age-specific 20-m SRT percentiles and curves were extracted for four common 20-m SRT metrics (laps, completed stages/minutes, speed at the last complete stage, estimated peak oxygen uptake). We also estimated the prevalence of healthy CRE according to the interim international cut-points (42 mL.kg-1min-1 for boys, 35 mL·kg·1min-1 for girls). Chinese boys consistently outperformed girls, while more girls (86.4%) exhibited healthy CRE than boys (67.1%). Younger children and youth were more likely to meet the standards compared with the older, regardless of sex. Chinese children and youth underperformed international norms by 0.85% for boys and 3.1% for girls. The performance indicator (z-score) of Chinese children and youth was -0.01, indicating that 20-m SRT performance was worse than the international mean. The sex differences were also higher for international than Chinese students. This study provided national sex- and age-specific 20-m SRT Chinese norms, offering a valuable tool for screening, monitoring and identifying target groups for future interventions and early prevention of cardiovascular risk factors.

Association between soybean product consumption and executive function in Chinese Tibetan children and adolescents.

Objective: This sought to explore the association between soybean product consumption and executive function (EF) in Chinese Tibetan adolescents in high-altitude areas. Methods: A total of 1,184 Tibetan children and adolescents were tested on demographic variables, soybean product consumption, and executive function in Lhasa and Nagchu regions of Tibet, China, using stratified whole population sampling. One-way ANOVA, linear regression analysis, and logistic regression analysis were used to analyze the associations existing between soybean product consumption and executive function. Results: The proportions of Hardly ever, Occasionally, and Often in Soy Consumption among Tibetan children and adolescents in high altitude areas of Tibet, China were 21.7, 50.3, and 28.0%, respectively. The difference in 2 back reaction time among Tibetan children and adolescents with different soybean product consumption was statistically significant (F = 6.374, p = 0.002). The difference in conversion function reaction time was also statistically significant (F = 8.129, p < 0.001). Taking the soybean product consumption ≥6 t/w group as the reference group, after adjusting the relevant factors, those with soybean product consumption ≤1 t/w showed a statistically significant increase in Inhibit Function Dysfunction (OR = 1.844, 95% CI: 1.152, 2.951) and Conversion Function Dysfunction (OR = 2.008, 95% CI: 1.106, 3.646) had an increased risk of Conversion Function Dysfunction (OR = 2.008, 95% CI: 1.106, 3.646), which was significantly different (p < 0.05). Conclusion: There is an association between soybean product consumption and inhibitory control and translational flexibility of brain executive functions in Chinese Tibetan children and children and adolescents at high altitude.

Association between sleep quality and psychological symptoms: A cross-sectional survey of Chinese university students performed during the COVID-19 pandemic.

Background: Since the start of the coronavirus 2019 pandemic, people have faced many challenges, including in relation to sleep quality and psychological health. This study aims to analyze the association between sleep quality and psychological symptoms among university students in China, and to provide reference data to facilitate the development of interventions to improve the physical and mental health of university students. Methods: A stratified cluster sampling method was used to investigate the sleep quality and psychological symptoms of 6,363 university students in China. The Chi-square test was used to analyze differences in sleep quality among groups. Logistic regression analysis was used to analyze the association between sleep quality and psychological symptoms. Results: The proportions of Chinese university students with good, medium, and poor sleep quality were 25.73, 10.99, and 63.28%, respectively. The overall rate of psychological symptoms was 16.5%. Logistic regression analysis showed that, in general, university students with poor sleep quality had a higher risk of psychological symptoms than those with good sleep quality (OR = 1.53, 95%CI: 1.28, 1.84, p < 0.01). Compared with university students with good sleep quality, those with poor sleep quality were more likely to experience emotional symptoms (OR = 1.62, 95%CI: 1.36, 1.94), behavioral symptoms (OR = 1.55, 95% CI: 1.3, 1.84), and difficulties with social adaptation (OR = 1.84, 95% CI: 1.51, 2.25) (all p < 0.01). Conclusion: There was an association between sleep quality and psychological symptoms among Chinese university students. University students with poor sleep quality have a higher risk of psychological symptoms. Measures should be taken to improve the sleep quality of university students and reduce the incidence of psychological symptoms. This study provides reference data for government and education departments that could inform public health policies.

Association between Sleep Quality and Depression Symptoms in Chinese College Students during the COVID-19 Lockdown Period.

Background: The outbreak of COVID-19 has seriously threatened the health of people around the world. To prevent the spread of the epidemic, Chinese universities have implemented closed management of campuses. The implementation of restrictive measures has gradually caused changes in the quality of sleep and the psychological state of college students. In addition, college students are faced with the dual pressure of employment and study, and the psychological pressure is huge. Therefore, it is necessary to investigate sleep and depressive symptoms among college students. Methods: Using the method of stratified cluster sampling, 6695 college students were selected from three universities in Jiangxi, Anhui, and Xinjiang provinces from April to May 2022. The Chinese version of the Pittsburgh sleep quality index (PSQI) and the self-rating depression scale (SDS) were used for the survey. Hierarchical logistic regression analysis was used to analyze the relationship between the PSQI and the SDS. Results: Overall, during the outbreak of COVID-19, 69.0% of males and 73.5% of females had poor sleep quality among Chinese college students and the detection rate of depressive symptoms was 43.6% for males and 47.8% for females, respectively. Taking students with good sleep quality as references, after controlling for covariates, hierarchical logistic regression shows that Chinese college students with poor sleep quality have a higher OR value (OR = 12.0, 95%CI: 10.2~14.1, p < 0.001), especially in males (OR = 43.8, 95%CI:30.2~63.6, p < 0.001). For both males and females, the OR value of college students with the following characteristics was higher: rural college students (males, OR = 50.32, 95%CI: 32.50−77.93; females, OR = 8.03, 95%CI: 6.45−9.99), overweight college students (males, OR = 62.17, 95%CI: 19.47−198.53; females, OR = 16.67, 95%CI: 6.48−42.88), and college students drinking sugar-sweetened beverages (males, OR = 59.00, 95%CI: 36.96−94.18; females, OR = 8.16, 95%CI: 6.63−10.05) (p < 0.001). Conclusions: Poor sleep quality is associated with depressive symptoms among Chinese college students, especially college males. Our research suggests that it is necessary to consider the improvement of sleep quality and depressive symptoms among college students during the COVID-19 epidemic.

Association Between Sugar-Sweetened Beverage Consumption and Executive Function Among Chinese Tibetan Adolescents at High Altitude.

Objective: To estimate the association between sugar-sweetened beverage (SSB) consumption and executive function (EF) among Chinese Tibetan adolescents. Method: Using three stages by stratified cluster sampling, 1,427 Chinese Tibetan adolescents were recruited from Tibet, China. SSB consumption status was obtained by questionnaires and the three core EFs (inhibition, working memory, and cognitive flexibility) were tested by a modified Eriksen flanker task, N-back shift, and a more-odd shifting task. One-way ANOVA or Chi-square test was used to compare SSB consumption in different categories. Taking the SSB consumption 0 time/week group as the reference, general linear regression (for continuous variable) or Logical regression (classified variable) in three Models was conducted to analyze the relationship between SSB consumption and EF for Chinese Tibetan children and adolescents. Result: After adjustment of all the covariant in Model 2, all the EF indexes were higher in Chinese Tibetan adolescents with SSB consumption ≥2 times/week than that with SSB consumption of 0 times/week by 21.33 ms (95%CI: 6.72, 35.93), 8.21 ms (95%CI: 7.06, 9.35), 90.46 ms (95%CI: 28.69, 152.23), 147.61 ms (95%CI: 81.42, 213.80), 116.18 ms (95%CI: 74.48, 157.87), 112.41 ms (95%CI: 71.30, 153.52) for incongruent RT, RT difference in incongruent and congruent, 1-back RT, 2-back RT, Heterogeneous RT, RT difference in Heterogeneous and Homogeneous respectively. Conclusions: The results suggested that SSB consumption was associated with poorer EF in Chinese Tibetan adolescents. SSB consumption should be controlled for healthy brain development of Chinese Tibetan adolescents.

Association of sugar-sweetened beverage consumption with psychological symptoms among Chinese university students during the COVID-19 pandemic.

Background: Mental health of college students has become a public health issue of common concern worldwide. Especially during the COVID-19 pandemic, the problem has become even more acute. The aim of this study was to assess the association between sugar-sweetened beverages (SSB) consumption and psychological symptoms among Chinese college students in order to promote their mental health. Methods: The study population was 6,120 college students aged 19-22 years from Anhui, Henan and Xinjiang, China. Basic demographic information, covariates and SSB Consumption data were collected through a self-assessment questionnaire. The "Multidimensional Sub-health Questionnaire of Adolescents" was used to assess the psychological symptoms of college students. The Chi-square test, one-way ANOVA and logistic regression analysis were used to investigate the differences and associations between SSB consumption and psychological symptoms among Chinese college students. Results: The detection rate of psychological symptoms among Chinese college students was 8.1%. The detection rate of boys students was 9.4% and that of girls students was 7.1%, and the difference was statistically significant in comparison (χ 2-value was 11.08, p < 0.001). After controlling for covariates, Model 2 analysis showed that compared to SSB consumption <2 time/week, college students with SSB consumption ≥2 time/week (OR = 2.96, 95% CI: 2.36, 3.70) had a higher risk of psychological symptoms (p < 0.001). The same trend was found for emotional symptoms, behavioral symptoms, and social adaptation difficulties dimensions. Conclusion: There is an association between SSB consumption and the occurrence of psychological symptoms among Chinese college students. Future measures should be taken to reduce both SSB consumption and the incidence of psychological symptoms.

Physical fitness reference standards for Chinese children and adolescents.

To develop age- and sex-specific physical fitness reference standards and express the age- and sex-related differences using standardized effect sizes for Chinese children and adolescents. A total of 85,535 children and adolescents (48.7% girls) aged 7-18 years were recruited from six geographical divisions of China using a stratified randomized cluster sampling method. Seven physical fitness items including grip strength, standing long jump, 30-s sit-ups, sit and reach, 50-m dash, 20-s repeated straddling, and 20-m SRT were measured following a standardized procedure. Percentile curves for each physical fitness test were calculated using the LMS. Age- and sex-related differences were expressed as standardized effect sizes. We observed that the performance improved with age along with the analyzed percentiles in all tests. Boys had higher values compared to girls in all the physical fitness items except for sit and reach test, where girls showed better performance in all analyzed percentiles. Also, the sex differences increased with ages except sit and reach. There is a need for a differentiated approach in the physical education class in terms of adjustment of physical activity based on sex, level of fitness abilities in China.

Secular Trend in the Physical Fitness of Xinjiang Children and Adolescents between 1985 and 2014.

We assessed trends in physical fitness by age group and nutrition status among children and adolescents in Xinjiang during 1985-2014. The data of 49,357 participants aged 7-18 were extracted in 1985, 1995, 2005, and 2014. Growth and nutritional status were defined using World Health Organization definitions. A physical fitness indicator (PFI) was calculated as the sum of six components measured in every survey. The relationship between body mass index (BMI) and PFI was investigated using nonlinear regression. Taking 1985 as a reference, PFI increased to 2 in 1995 and then fell sharply to -2.8 in 2005 and -3.8 in 2014. The prevalence of normal weight increased from 87.5% in 1985 to 89.4% in 1995 and then decreased to 75.2%, consistent with the change in PFI. The relationship between BMI and PFI showed an inverted U-shaped curve. The largest increment occurred in boys aged 13-15 and girls aged 16-18 during 1985-1995; the largest decline occurred in boys and girls aged 10-12 during 1995-2005. Our research provides a reference for local governments providing nutrition subsidies and projects in southern Xinjiang, indicating that greater attention is needed for children aged 7-12.

Isotemporal substitution of sedentary behavior for physical activity on cardiorespiratory fitness in children and adolescents.

Both sedentary behavior (SB) and physical activity (PA) are associated with cardiorespiratory fitness (CRF) and independent of each other. Due to the limited time during school for children and adolescents, it is necessary to explore the isotemporal substitution of SB for PA on CRF.A total 536 eligible participants selected from the 7 traditional administrative regions of China were included in this study. The outcome was CRF, determined using a 20-meter shuttle run test, and exposures were SB, light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA) measured with accelerometers. We analyzed the cross-sectional associations of substituting SB with LPA, MVPA, and combinations of LPA and MVPA with CRF, using an isotemporal substitution model.Reallocating SB into MVPA was associated with higher CRF for male (P < .01) and female (P < .01) children and female adolescents (P < .05). In the mixed redistribution, the ratio of LPA to MVPA for male children and female adolescents started from 16:4 and 14:6, respectively, tended toward improvements in CRF. For female children, regardless of the ratio of LPA to MVPA, it was always associated with higher CRF.Reallocating SB into MVPA isotemporally was positively associated with CRF for male and female children and female adolescents but not for male adolescents. MVPA is the key factor to improve CRF when combinations of LPA and MVPA replace SB. The combined approach can provide basis for the selection of target and monitoring variables in intervention studies, and has more flexible choices for improving CRF that are more consistent with the daily PA habits of children and adolescents.

Levels of Physical Fitness and Weight Status in Children and Adolescents: A Comparison between China and Japan.

This study compared the physical fitness level and weight status of children and adolescents in China and Japan. Children and adolescents aged 7-18 years were recruited (China: n = 5660; Japan: n = 5660). Physical fitness was assessed using seven core items-grip strength, 30-s sit-ups, standing long jump, sit-and-reach, 20-s repeated straddling, 20-m shuttle run test, and 50-m dash. A physical fitness index (PFI) was calculated by adding all items' Z-scores. We conducted comparisons of PFI and its distribution, each physical fitness item, and weight status for individuals from China and Japan across all ages. The PFI was lower in China than in Japan for all age groups, with an especially large difference at age 18 years for boys (a difference of 9.05) and girls (a difference of 9.10) (p < 0.001). The same result was seen for the seven items. The PFI distribution for children and adolescents was more disperse among those in Japan than among those in China. Obesity prevalence was 2.84 times higher in China than in Japan. An inverted U-shaped relationship was observed between physical fitness and nutritional status. Children and adolescents showed markedly lower physical fitness and higher obesity prevalence in China than in Japan.

Benefits of normal body mass index on physical fitness: A cross-sectional study among children and adolescents in Xinjiang Uyghur Autonomous Region, China.

OBJECTIVE: To assess the association between body mass index (BMI) and physical fitness index (PFI) among children and adolescents in Xinjiang Uyghur Autonomous Region, China. METHODS: In total, 17,618 children and adolescents aged 7-18 years from the selected region were enrolled in this cross-sectional study (8,800 boys and 8,818 girls). Participants were stratified by age and sex and divided into five groups by BMI percentiles: very low (BMI <5th percentile); low, (5th ≤ BMI < 15th percentile); normal (15th ≤ BMI < 85th percentile); high (85th ≤ BMI < 95th percentile); and very high (BMI ≥95th percentile). PFI was assessed by height, weight, and five health-related fitness indicators (grip strength, standing long jump, sit and reach, 50 m dash, and endurance run). RESULTS: BMI was significantly associated with PFI during adolescence (13-18 years) in boys and pre-adolescence (7-12 years) in girls. Between the ages of 13 and 18 years, an increase in BMI had a greater impact on PFI in boys than girls. PFI showed a parabolic curvilinear relationship with BMI. CONCLUSION: Children and adolescents in China's Xinjiang Uyghur Autonomous Region with a normal BMI demonstrated good physical fitness. A BMI below or above the normal range may contribute to poor physical fitness. The relationship between BMI and PFI shows an inverted U-shaped curve.