Abstract In recent decades, the development of the physical health and mental health of adolescents in China has not been viewed optimistically. It is necessary to explain the relationship between the physical health and mental health of adolescents to improve their health. Given the above background, the author completed an in-depth discussion and analysis of the relationships between body shape, fitness and adolescent mental health, aiming to provide a theoretical basis for establishing a reasonable and scientific intervention mechanism and promoting the healthy development of adolescents in China.

Objective: This paper analyses the secular trend in physical growth among Japanese children and adolescents from 1900 to 2016, and to provide scientific reference for growth and development in Chinese adolescents. Methods: Data of height and weight of Japanese children and adolescents aged 6-17 years from 1900 to 2016 included in the Survey of School Health Care were used to illustrate growth rate and range of height, weight and BMI during different periods by using one-way ANOVA. Longitudinal correlation between height, weight and BMI was analyzed by using longitudinal analysis method. Results: During 1900 to 2016, height growth ranged between 9.5-19.9 cm in boys and 10.8-18.9 cm in girls aged 6-17 years and the weight growth ranged between 4.0-15.9 kg in boys and 3.9-14.2 kg in girls, with males significantly higher than females; Peak height and weight growth rate of Japanese children and adolescents occurred between 1950 and 1960 (boys: 4.8 cm and 2.7 kg; girls: 3.9 cm and 2.4 kg). On the contrary, from 1939 to 1950, height and weight of Japanese children and adolescents showed a significant decreasing trend (boys: -1.8 cm and -1.2 kg per 10 years; girls: -0.8 cm and -0.4 kg per 10 years); During 2000-2016, the growth rates of height of boys and girls in all age groups in Japan were -0.2 to 0 cm in boys and -0.2 to -0.1 cm in girls per 10 years, respectively. Conclusion The long-term growth trend of Japanese children and adolescents shows an increasing trend before and after World War II; During World War II and the early post-war period, Japanese children and adolescents showed long-term decreasing trend. In the 21st century, the slow decreasing trend in growth among Japanese children and adolescents is observed, which might associate with absence of favorable environment.

Objective: To determine the relationship between mental sub-health and dietary behavior among Chinese adolescents, and to provide a scientific basis for improving adolescent mental sub-health through healthy dietary behavior. Methods: A total of 16 545 adolescents aged 13 to 22 years were sampled by random cluster sampling method in six administrative regions of China. A questionnaire survey was conducted to investigate adolescents’ dietary behaviors and mental sub-health status. Results: The proportion of boys consuming breakfast, snacks, carbonated drinks, vegetables, fish and dairy products was 76.2%, 20.2%, 19.0%, 78.4%, 52.4% and 59.2%, respectively, while the proportion of girls was 79.2%, 28.6%, 12.6%, 78.3%, 43.2% and 54.9%, respectively. Except for the "vegetable" option, dietary behaviors showed significant sex differences(χ2=20.79,320.10,229.06,150.27,32.21,P<0.01). In terms of mental sub-health, the detection rates of male adolescents’ mental sub-health status, behavioral sub-health and social sub-health were 20.7%, 26.0% and 17.2%, respectively, while those of female adolescents were 18.6%, 24.1% and 14.8%, respectively. The differences between boys and girls were statistically significant (χ2=17.32,7.66,17.46,P<0.01). Controlling for age and gender, breakfast "normally eating" and "occasionally eat", vegetables "normally eating" and "occasionally eat", fish "normally eating" and "occasionally eat", milk, dairy products "normally drink" and "occasional drink",was negatively associated with teenagers’ psychological sub-health (OR=0.60,0.73;0.50,0.65;0.74,0.77;0.73,0.69,P<0.05). Conclusion Healthy dietary behavior could be protective to avoid adolescent mental sub-health.Nutritional lectures and guideline books are needed among students and their parents.Nutritionists are encouraged to provide healthy nutritional advice to school canteen.

Objective: To explore the characteristics and related factors of adolescent executive function, so as to provide theoretical basis for promoting the development of adolescent executive function. Methods: A total of 5 018 adolescents aged 13-18 from Shanghai, Suzhou, Taiyuan, Wuyuan, Xingyi and Urumqi were selected by convenient cluster random sampling method from September to December 2022, and their basic information, family status, lifestyle behavior, physical fitness and executive function were investigated by questionnaire survey. Considering the heterogeneity between schools, a multilevel Logistic model was established to analyze the related factors of adolescent executive function. Results: The inhibitory function of high school students was better than that of middle school students (Z=-2.69). In terms of refreshment function, high school students were superior than middle school students (1-back:Z=-11.32; 2-back:Z=-11.36), and male students were superior than female students (2-back:Z=-2.18); in terms of shifting function, high school students were superior than middle school students (Z=-2.63), and boys were superior than girls (Z=-7.10)(P<0.05). The results of multilevel model analysis showed that the executive function of adolescents was clustered at the school level. At the individual level, junior high school refreshment function (1-back:β=56.94; 2-back:β=127.00), and shifting function (β=35.64) were worse than that of high school students; the refreshment function 2-back (β=-21.24) and shifting function (β=-28.42) of male students were better than those of female students; the refreshment function 2-back of nononly child was better than that of only child (β=-19.36); refreshment function of low fitness was worse than that of high fitness (β=37.35); the shifting function of the video screen time not up to standard was better than that of the standard (β=-14.30)(P<0.05). Conclusions The executive function of high school students is better than that of middle school students, the refreshment function and shifting function of boys are better than that of girls. Family environment, lifestyle and physical health are significant factors related to executive function of Chinese adolescents. By raising awareness of the major supporting and impeding factors for executive functioning in adolescents, it can help to develop effective intervention programs for adolescents.

Objective: To analyze the correlation between physical activity and physical fitness index of children and adolescents in China, so as to provide reference for physical activity and physical fitness promtion of children and adolescents. Methods: In September 12,2018, 4 269 students were selected by cluster sampling in east, northwest, north, central, southwest and South China, the test of standing long jump, grip strength, 50 m running, improved seat forward bend, 30 s sit ups, 20 s cross repeatedly, 20 m round trip running was completed. Results: In comparing the physical fitness index of children and adolescents with different levels of physical activity, the PFI values of the middle and high intensity physical activity (MVPA) groups of boys aged 10-12 and 16-18 years old were (0.46±3.58) (0.75±3.0), the value of PFI of the MVPA group were (-0.69±3.64) (-0.61±2.87), the difference was statistically significant ( t =0.04, 0.57, P >0.05). There was no significant difference in the values of PFI between the four age groups of the girls ( P <0.05). In comparison of physical activity status of children and adolescents in different physical ability grades, the time of MPA, VPA and physical exercise in healthy physical ability group was higher than that in unhealthy physical ability group ( Z =-2.04, -4.93, -7.09, P <0.05). Linear regression analysis showed that there was a positive correlation between daily MVPA, physical exercise and physical fitness index ( P <0.05). Conclusion Moderate and high intensity physical activity, that is, physical exercise, is positively correlated with physical fitness index. Therefore, it is particularly important for children and adolescents to engage in sufficient moderate and vigorous intensity physical activities.

Objective: To understand the mental sub-health status of Chinese adolescents and its correlation with muscle strength index, and to provide information for relevant research in mental health and muscle strength development of Chinese adolescents. Methods: A total of 16 545 adolescents aged 13-22 year-old in six administrative regions of China were administered with the Adolescent Sub-Health Multidimensional Assessment Questionnaire (MSQA). Muscle strength indicatros were tested and its relations with mental sub-health were analyzed. Results: The detection rates of Chinese adolescents emotional problems, character problems, social adjustment difficulties, and mental sub-health status were 25.5%, 25.0%, 16.0%, and 19.7%, respectively. The detection rates of mental sub-health status of adolescents in the group of muscle index P75 were 30.3%, 19.0%, and 10.4%, respectively, and the difference was statistically significant(χ2=522.03, P<0.01). Logistic regression analysis showed that junior high school(OR=2.55), high school(OR=2.27), male students(OR=1.15), muscle index Conclusion There is a correlation between the mental sub-health of Chinese adolescents and the muscle strength index. The higher the muscle strength index, the lower detection rate of mental sub-health.

Objective: To investigate the association between mental sub-health and physical fitness of Chinese adolescents, to provide a reference for promoting the physical and mental health of Chinese adolescents. Methods: A total of 16 545 adolescents (13-22 years) were selected by random cluster sampling in six major administrative regions in China. The psychological part of the Multidimensional Sub-health Questionnaire of Adolescents (MSQA) and the physical fitness index test were used to assess mental sub-health and physical fitness, respectively. The chi-square test and Logistic regression analysis were used to analyze and compare the relationships between different levels of physical fitness and mental sub-health. Results: The overall detection rate of mental sub-health status among high-grade physical fitness index adolescents was 11.9%, and the detection rate among low-grade physical fitness index youths was 26.0%, and the difference was statistically significant (χ2=970.73，P<0.05). The overall detection rate among high-grade physical fitness index boys was 11.1%, and that of low-grade physical fitness index boys was 24.4%. The difference was statistically significant (χ2=566.12，P<0.05). The overall detection rate of mental sub-health status among high-level physical fitness index girls was 12.8%, and that among low-level physical fitness index girls was 27.6%, and the difference was statistically significant (χ2=412.25，P<0.05). After adjusting for gender, age, BMI, and region in the Logistic regression model, the detection rate of mental sub-health status of adolescents with low-grade physical fitness index was 2.35 times higher than that of high-grade physical fitness index adolescents(95%CI=2.12-2.61). Conclusion Adolescents with poor physical fitness have a higher risk of mental sub-health.Attention should be paid to adolescent physical fitness development to comprehensively improve physical and mental health development.

Objective: To understand the relationships between video time, exercise time and the mental sub-health of Chinese adolescents, and to assist the development of Chinese adolescents’ mental health. Methods: In this study, 16 545 adolescents aged 13-22 years in six administrative regions of China were surveyed using an adolescent sub-health multi-dimensional assessment questionnaire (MSQA), and daily physical exercise time, video screen time and other indicators were recorded. Binary Logistic regression analysis was used to understand adolescents’ mental sub-health and the correlation between video time and exercise time. Results: Detection rate of mental sub-health status in adolescents with video time ≤2 h/d was lower than that of adolescents with video time >2 h/d(19.1%，22.1%), and the detection rate of adolescents with exercise time ≤60 min/d(22.1%，17.7%) was higher than that of adolescents with exercise time >60 min/d. These differences were statistically significant (χ2=14.47, 6.97, P<0.05). Binary Logistic regression analysis showed that the risk of mental sub-health status for Chinese adolescents whose screen time was more than 2 h/d was 1.20 times that of those with screen time ≤2 h/d, and the difference was statistically significant (P<0.01). The risk of mental sub-health for students whose exercise time was > 60 min/d was 0.86 times that of students who exercised ≤ 60 min/d, and the difference was statistically significant (P<0.05). Conclusion Screen time >2 h/d and exercise time <60 min/d were negative factors leading to mental sub-health symptoms in Chinese adolescents.It is proposed to jointly promote the healthy adolescent development through health education,as well as positive family and social environment.

Objective: To explore the correlation between different nutritional status and mental sub-health of Chinese adolescents, and provide reference for improving the physical and mental health of Chinese adolescents. Methods: A total of 16 545 adolescents (13-22 years old) were selected by random overall sampling method in six major administrative regions in China.The psychological part of the Multidimensional Sub-health Questionnaire of Adolescents (MSQA) was used for mental sub-health test.Chi-square test and Logistic regression analysis were used to analyze and compare the relationship between different nutritional status and mental sub-health. Results: The overall detection rate of mental sub-health status in the adolescents with normal BMI group was 18.5%, while those in the lean, overweight and obese groups were 22.3%, 38.7%, and 44.7%, respectively, which were significantly different from those in the normal BMI group(χ2=478.68，P<0.05).After adjusted for gender and age, the Logistic regression model showed that compared with those with normal BMI, those who were thin (OR=1.19, 95%CI=1.09-1.30), overweight (OR=2.76, 95%CI=2.47-3.09) and obese(OR=3.43, 95%CI=2.83-4.15) had increased risk of mental sub-health. Conclusion The nutritional status of Chinese adolescents in significantly related to mental sub-heatlh,hose who are underweight, overweight and obese have significantly higher risks of mental sub-health than those who are normal.Improvement of nutritional status of adolescents is beneficial to healthy adolescent development.

Objective: To understand physical activity status and its relation with cardiopulmonary endurance among Chinese children and adolescents, so as to provide reference for cardiopulmonary endurance improvement and intervention of Chinese children and adolescents. Methods: During September to November 2018, a stratified cluster sampling method was used to select 4 269 children and adolescents aged 7-18 years in six major regions of China, 20 m shuttle run test and physical activity were assessed. Results: Average duration for daily lowintensity physical activity among boys was (31.49±30.01) min, for moderate to vigorous physical activity (68.37±46.50) min. Average duration for low intensity physical activity among girls was (34.02±31.58) min, for moderate to vigorous physical activity was (63.02±44.91) min. The number of 20 m shuttle run test for boys reached ( 36.17 ±21.94) times, and the maximal oxygen uptake per minute was (44.51±5.05) mL/kg; the number of 20 m shuttle run test for girls reached (26.59±12.56) times, and the maximal oxygen uptake per minute was (41.99±5.29) mL/kg. There were statistically significant differences in the number of 20 m shuttle run test and maximal oxygen uptake across age groups in boys ( F= 589.37 , 152.79, P <0.01), as well as that in girls ( F=305.21, 1 032.46, P <0.01). The proportion of boys and girls who met moderate to vigorous physical activity standard was 49.24% and 42.92%, respectively. Linear regression analysis showed that there was a significant positive correlation between the duration of moderate to vigorous physical activity and maximal oxygen uptake ( β=0.11, P ＜ 0.01). Conclusion There is a significant correlation between moderate to vigorous physical activity with cardiorespiratory endurance among Chinese children and adolescents. Higher level of moderate to vigorous physical activity is important to help improve cardiopulmonary endurance among children and adolescents.