Objective: To explore the relationship between family background and parental support and adolescents physical activity and motor skills, and to provide a corresponding theoretical basis for the health promotion of children and adolescents in China. Methods: From November to December 2019, 140 junior high school students aged 12-14 years in a junior high school in Shanxi Province were selected, and physical activity was recorded for 7 days using an ActiGraph GT3X+ accelerometer. The Activity Support Scale for Children (ACTS CN) was used to evaluate parents support and attitude towards children s activities and behaviors. The Canadian Agility and Movement Skill Assessment (CAMSA) was used to evaluate the motor ability development of adolescents. Results: The daily participation time in moderate to vigorous physical activity (MVPA) was (40.57±13.54) and (31.65± 9.98 ) min for males and females, respectively, with a statistically significant difference ( t =4.44, P <0.05); The average motor skill scores were (10.8±1.9) and (10.1±1.9), and completion times were (17.7±2.8) and (19.1±2.5)s, respectively; regression analyses showed that mothers education, monthly household income, mothers attention to children s exercise and fathers support for club participation were all significantly associated with adolescents MVPA ( B =-0.28,-0.16,-0.16, 0.18, P <0.05). Parental provision of exercise space was significantly associated with motor ability ( r =0.17, 0.17, P <0.05). Conclusion Parents with higher levels of education have a more positive influence on their children s physical activity participation. Parental presence can contribute to a certain extent to the level of physical activity of adolescents, and a supportive environment provided from parents can positively influence the level of motor skills of adolescents.

Objective: To analyze diurnal variation of moderate to vigorous physical activity (MVPA) and sedentary time among adolescents, to further explore the possible factors associated with diurnal variation of adolescents physical activity and to provide reference for appropriate intervention strategies. Methods: A total of 148 middle school and high school students in Beijing were assessed for daily MVPA and sedentary time by wrist worn ActiGraph GT3X three axis accelerometers for one week. Height and weight were measured. Results: The MVPA [(49.39±30.36)min/d] on weekdays was higher than that on weekends[(34.24± 30.30 )min/d]( t=6.61, P <0.05). The MVPA of boys on weekdays and weekends was higher than that of girls( t=4.42, 2.18 , P <0.05). The sedentary time on weekdays and weekends was(566.48±156.84) and (588.55±152.93)min/d, respectively, and the difference was not statistically significant( t=-0.21, P >0.05). The sedentary time of boys was lower than that of girls( t=-8.20, -2.51 , P <0.05). The coefficient of variation of adolescent MVPA was lower on weekdays(0.39±0.17) than on weekends(0.59± 0.46 ), and the difference was statistically significant( t=-3.23, P <0.01). There was no significant difference in the coefficient of variation between weekdays (0.17±0.08) and weekends(0.15±0.13)( t=1.10, P >0.05). The coefficient of variation(0.52±0.18) of MVPA in adolescents was higher than that of sitting(0.18±0.07)( t=14.43, P <0.01). Conclusion Adolescents have higher level of physical activity on weekdays, and high level of physical inactivity on weekends. MVPA time variation is higher within a week, especially on weekends, sedentary time is steadily at a high level. The finding suggests that in addition to the active measures taken by schools to increase the physical activity of students, interventions for girls and weekends are particularly important to increase the overall level of physical activity for adolescents.

Objective: To investigate the variability of the time and frequency of Moderate to Vigorous Physical Activity (MVPA) during the school days and weekends of junior high school students, and to explore the correlation between MVPA and physical fitness. Methods: A cluster sampling method was used to investigate 79 students of grade 1 and grade 2 in Beijing Huilongguan Middle School. Adapted one day physical activity recording tool was implemented to investigate students’ physical activity from 8:00 to 23:00 a week, activity records were classified into daily MVPA parts and non MVPA parts based on MET values. Physical activity time series for 5 consecutive days and 2 weekends, as well as MVPA total time and the lempel ziv complexity of the sequence was calculated. Investigated the correlation between the MVPA situation and the results of national students’ physical fitness standard test. Results: There was no statistical difference in MVPA time between males and females during school days( t =-0.90, P >0.05). Females had greater variability in MVPA than males(58.9%, 53.5%). There was also no statistical difference in MVPA complexity between genders( t =-0.55, P >0.05). During weekends, there was no significant difference in the total MVPA time between men and women( t =-0.13, P >0.05). The CV of male MVPA time was lower than that of female(141.5%, 152.8%). There was also no significant difference( t =-0.63, P >0.05), and male MVPA complex CV was slightly higher than that of female ( 55.1% , 48.1%). The MVPA time CV of adolescents during weekdays was slightly lower for males (weekdays vs weekends: 53.5%, 141.5%) than females(58.9%, 152.8%). The MVPA complexity in weekdays among males was moderately correlated with BMI( r =0.41), and the MVPA time and weight of females ( r =-0.30) and BMI ( r =-0.31) were low. The complexity was related to body weight ( r =-0.31) and BMI ( r =-0.33) to a low degree( P <0.05). Conclusion Junior middle school students are more active on school days than weekend, but the MVPA time series are limited. Schools can effectively improve physical fitness by spreading out the activity period of MVPA in one day. MVPA complexity, as a more comprehensive indicator, may be more sensitive to BMI of junior middle school students.