Objective To compare the effect of a carbohydrate-electrolyte-protein solution (CEPS,2％ protein plus 4％ carbohydrate),carbohydrate-electrolyte solution (CES,6％ carbohydrate),and non-caloric sweetened placebo (PLA)on 21 km running performance of female recreational marathon runners.Methods In a randomized cross-over design,12 female recreational marathon runners (age:33.4 ± 2.1 years,body mass index:21.10 ± 0.6 kg/m2,and maximal oxygen consumption:48.5 ± 1.9 mL/kg/min)performed a 21 km time trial (TT)run on three occasions separated by at least 28 days.During the first 5 km,participants ran on the treadmill with 70％VO2max.Thereafter,the participants ran at whatever speed they wished for the remaining 16 km of the performance run.In each main trial,participants ingested the CEPS,CES,or PLA at a rate of 150 mL every 2.5 km.The blood samples,gas samples,heart rate,core temperature,and subjective measures were conducted every 5 km throughout the exercise.Results Time of TT run completion was slightly shorter (P ＜ 0.05)in the CES trial (97.8 ±1.6 min)than in the PLA trial (102.4 ± 2.4 min),with no significant differences between the CEPS trial (100.7 ± 2.9 min)and the other two trials (P＞0.05).There were no differences in core temperature,blood lactate,heart rate,CHO oxidation rate,fat oxidation rate,CHO oxidation amount,and fat oxidation amount among the different trials (all P＞0.05).The average blood glucose was higher in CES trial than PLA trial (P＜0.05).The average respiratory exchange rate was higher in CEPS trim than PLA trial (P＜0.05).Conclusion Compared with ingesting the PLA,ingesting the 6％ CES improves the 21 km TT run performance in recreational female runners.However,no additional benefit of CEPS was observed on endurance performance.

Objective: This study aims to determine the prevalence of overweight and obesity and associated early life factors among children aged 2 to 6 years in a community in Guangzhou. Methods: A stratified cluster sampling was used to select 922 children from one community in Guangzhou in 2018. The survey included a questionnaire survey and physical examination. Logistic regression analyses were performed to examine the relationship of early-life factors and obesity. Results: The prevalence of overweight and obesity was 13.4% in 922 children(16.1% in boys and 10.1% in girls). The sex difference in prevalence of overweight and obesity was statistically significant(Z=2.69, P<0.05). Overweight and obesity was found significantly higher in children with large for gestational age, caesarean section, artificial feeding within 6 months, maternal pre-pregnancy overweight and obesity, maternal excessive weight gain(P<0.01). Large for gestational age (OR=2.62, 95%CI=1.42-4.82), caesarean section(OR=1.59, 95%CI=1.08-2.36), artificial feeding within 6 months(OR=2.00, 95%CI=1.19-3.37), maternal pre-pregnancy overweight or obesity(OR=1.97, 95%CI=1.08-3.58), and excessive gestational weight gain (OR=2.07, 95%CI=1.26-3.39) was positively associated with childhood overweight obesity(P<0.05). Maternal pre-pregnancy underweight was negatively associated with childhood overweight obesity(OR=0.51, 95%CI=0.29-0.88, P<0.05). Conclusion Early-life risk factors are positively associated with the risk of overweight and obesity in later childhood, including large gestational age, caesarean section, artificial feeding within 6 months, maternal pre-pregnancy overweight and excessive gestational weight gain, while maternal pre-pregnancy underweight associates with low risk of child overweight and obesity. These findings suggest that early intervention to these modifiable risk factors could make a significant contribution to childhood obesity prevention.

Objective: To investigate the prevalence of metabolic syndrome (MS) and to explore the relationship of MS with screen time (ST) among children aged 6-13 years in Guangzhou, China. Methods: A total of 4 523 children aged 6-13 from 5 primary schools in Guangzhou were selected using stratified random cluster sampling method. Questionnaire was used to assess children’s basic demographic characteristics and ST. Children’s height, weight, waist circumference and blood pressure were measured objectively, and their blood glucose, triglyceride and high-density lipoprotein-cholesterol were tested. -Chi-square test was performed to compare the prevalence of MS in children among different ST levels. Logistic regression model was used to explore the association between ST and MS. Results: The prevalence of MS in children was 2.4%, and that among boys (3.0%) was higher than in girls (1.7%, P=0.01). children were classified into three groups according to duration of ST: low ST (less than 1 h), moderate ST (1-2 h), high ST (higher than 2 h, 9.0% of total participants). Prevalence of central obesity, triacylglycerol and MS in high ST group was significantly higher than children with low ST(P<0.05). Children with high level of ST showed higher risks of central obesity (OR=1.43, 95%CI=1.04-1.96) and MS (OR=1.94, 95%CI=1.11-3.40) compared with low-level ST group. Conclusion Higher level of screen time associates with an increased risk of MS in children, which suggest the importance of effective early intervention.

Objective: To investigate the associations of moderate to vigorous intensity physical activity (MVPA) and screen time (ST) with emotional and behavioral problems in children and to provide evidence for related intervention measures. Methods: In March 2017, a total of 4 922 children aged 6-12 years from 5 primary schools in Guangzhou were enrolled using stratified random cluster sampling method. Questionnaires were used to assess children s socio demographic information, MVPA, ST and emotional and behavioral problems. The associations of MVPA and ST with behavioral problems were explored by using generalized linear mixed models. Results: Students with MVPA≥60 min per day accounted for 37.5%, and with ST≤2 h per day accounted for 87.7%. Children who were physically active showed lower scores for total difficulties, hyperactivity, and peer problems and higher score for prosocial than inactive peers( t =2.80, 2.47, 2.56, -1.97, all P <0.05). Also, children who spent less than 2 h ST per day reported lower scores for total difficulties, emotional symptoms, conduct problems, hyperactivity, and peer problems and higher score for prosocial compared to those with high ST( t =3.18, 3.35, 3.70, 3.80, -3.21, 4.97, all P <0.05). Children who met neither MVPA nor ST recommendations had significantly increased risks of total difficulties( OR=1.73, 95%CI =1.12-2.68), conduct problems( OR=1.45, 95%CI =1.02-2.05), peer problems( OR=1.93, 95%CI =1.11-3.36), and prosocial ( OR=1.55, 95%CI =1.08-2.23) than those who met both. Conclusion MVPA and ST are independently related to children s emotional and behavioral problems, and the risks of emotional and behavioral problems increased in children with insufficient MVPA and longer ST.

Objective: To investigate the association between sedentary bouts and cardiovascular disease (CVD) risk factors, and to provide a reference for controlling and reducing the incidence of CVD in children. Methods: Cluster random sampling was used to select 356 students from five primary schools in Guangzhou. Sedentary behavior and physical activity were assessed using ActiGraph GT3X accelerometers, which were worn for 7 consecutive days. According to the sedentary bout duration of each participant, sedentary time was classified into categories of 1-<5, 5-<10, 10-<15, 15-<20 and ≥20 min bouts. Physical examinations were carried out to identify cardiometabolic risk factors. Multivariate linear regression was performed to analyze the relationship between sedentary bouts and CVD risk factors. Results: After adjusting for confounding factors, the time accumulated in sedentary bouts of 5-<10, 10-<15, 15-<20 min in duration were positively associated with higher cardiometabolic risk scores ( B =1.24， 2.01 ，2.40), negatively associated with lower HDL ( B =-0.13，-0.21，-0.27). The time accumulated in sedentary bouts of 1-<5, 5-<10 , 10-<15, 15-<20 min in duration were positively associated with BMI levels ( B =1.07，1.89，2.86，3.65), and waist circumference ( B =2.79，4.81，8.04，10.14)( P <0.05). Conclusion These results suggested that sedentary bouts of 5-<20 min were associated with an unfavorable cardiometabolic risk profile. Our finding suggests no more than 20 min accumulated sedentary time for children.

Objective: To investigate the associations between early life factors and the incidence of overweight and obesity and to provide a reference for childhood overweight and obesity prevention. Methods: A total of 5 172 children aged 6-11 years from 5 primary schools in Guangzhou were enrolled using stratified random cluster sampling method. After two years follow up, 3 315 children were included in the final analysis. Questionnaire was used to collect children s early life factors. Height and weight were measured objectively at baseline and follow up. Results: The incidence of overweight and obesity was 8.7% in children. After adjustment for confounders, results from the Logistic regression analysis showed that maternal pre pregnancy underweight was negatively associated with the incidence of childhood overweight and obesity( OR=0.54, 95%CI =0.38-0.76)( P <0.05). While excessive gestational weight gain during pregnancy( OR=1.55, 95%CI =1.14-2.10) and caesarean section ( OR=1.30, 95%CI =1.00-1.68) were positively associated with the incidence of childhood overweight and obesity( P <0.05). Conclusion Both excess gestational weight gain and caesarean section would increase the risk of the overweight and obesity of their offspring, while maternal pre pregnancy underweight would reduce the risk of childhood overweight and obesity.

Objective: To investigate the association of parental weight related knowledge, attitude and practice (KAP) with abdominal obesity among primary and middle school students and to provide evidence for related intervention measures. Methods: In September 2013, the multistage random sampling method was used to select 17 307 primary and secondary school students with normal waist circumference in seven provinces/municipalities in China. After nine month follow up, 14 118 students aged 6-18 years were included in the final analysis. Questionnaires were used to assess parental weight related KAP, and students’ waist circumference was measured objectively at baseline and follow up. Multiple linear regression and multivariate Logistic regression were conducted to analyze the relationship between parents’ KAP with the change of students waist circumference and abdominal obesity, respectively. Results: The nine month cumulative incidence of pre and abdominal obesity among students was 6.67% and 0.85%, respectively. The scoring rates of parents knowledge, attitude and practice were 80.17%, 78.17%, 50.50%, respectively. The score of parents weight related attitude was inversely associated with the changes of waist circumference ( β=-0.18, 95%CI = -0.26- -0.10) and cumulative incidence of pre and abdominal obesity ( OR=0.90, 95%CI =0.82-0.98)( P <0.05). Conclusion Parental positive and correct weight related attitude is inversely associated with the incidence of abdominal obesity among children and adolescents. Interventions targeting establishing parents correct beliefs may be an effective way to prevent abdominal obesity in children and adolescents.

Objective: To investigate the longitudinal association of plasma Irisin concentrations with changes in blood pressure (BP) levels among children,and to assess the moderating effect of physical activity (PA) or sedentary behavior (SB) on the relationship between Irisin levels and BP. Methods: Based on a cohort study, a cluster sampling method was used to select 3 651 school aged children from five schools in Guangzhou in 2017 at the baseline survey and follow up in 2019. Both at baseline and during follow up, PA and SB were assessed by validated questionnaires, and BP levels were measured by an electronic sphygmomanometer. A final sample of 521 children were enrolled based on the PA and SB at baseline. Plasma Irisin concentrations were measured by ELISA at baseline. Logistic regression analysis was recruited for exploring the associations of plasma Irisin concentrations with changes in BP. Moderating effects of PA and SB on the relationship between Irisin concentrations and BP were estimated using stratified analysis. Results: Logistic regression analysis indicated that there was no significant association between Irisin concentrations and changes in BP levels among children ( OR =0.98, P >0.05). After stratification for SB, Irisin levels in the low SB subgroup were inversely associated with changes in diastolic blood pressure ( OR=0.87, 95%CI=0.77-0.98, P =0.02). In addition, SB level had a moderating effect on the relationship between Irisin levels and the DBP changes ( P =0.01). Conclusion Increased Irisin concentration is associated with the decrease of DBP level among low SB children. Furthermore, SB level shows moderating role in the relationship between Irisin concentrations and changes in DBP levels.

Objective: To examine the association of sedentary behaviors with visual acuity among primary school children, and to provide a reference basis for the prevention and control of poor vision. Methods: Using stratified random cluster sampling method, a total of 4 969 students in grade 1-4 were selected from 5 primary schools in Guangzhou in 2017, and then were followed up in 2019. A validated questionnaire was used to collect data on children s sedentary behaviors, including doing homework, watching TV, playing computer/video games, and taking the bus/car between home and school. Visual acuity was measured in the baseline and the follow up using a 5 m standard logarithmic visual acuity chart. Multiple linear regression and Logistic regression were conducted to analyze the relationship between sedentary behaviors and visual changes. Results: The two year cumulative incidence of poor vision was 48.74%. Homework time was inversely associated with visual acuity of left eye( β=-0.012, 95%CI =-0.023- -0.002 ). Homework time was positively correlated with poor vision( OR =1.16, 95% CI =1.05-1.27). However, total sedentary time, screen time and bus/car time were not statistically associated with changes in visual acuity( P >0.05). Conclusion Increased homework time was associated with poorer vision in primary school students. Interventions to reduce the academic burden should be taken.