In the current study, we have explored the factors that associated with students MVPA level at baseline and the change of MVPA days in a 12-month follow-up. Our result demonstrated that there was no significant difference in MVPA level after a 12-month follow-up. Both school factors and neighborhood factors contribute to students MVPA level. In the longitudinal model, student’s attitude to PA has been found both affect the MVPA maintenance and development, meanwhile the PE class may also the be potential factor with a similar effect. Furthermore, the extra PA time and MVPA behavior of student’s parents are the contributor for maintaining the MVPA level, but not significantly for increasing MVPA level. However, students with more encourage from friends will increase their MVPA days in 12-month follow-up.
In the present study, there are no significant difference in MVPA days and levels between 2016 and 2017, although some of them change their PA behavior positively or negatively. However previous studies identified that MVPA decreasing with age in children and adolescent[25–27].Two large-scale questionnaire investigation studies have shown that the proportion of students met the MVPA guideline from 29.9% in 2016 to 34% in 2017 in China[8, 9]. It indicates that some factors influence the change trend. As the case might be influenced by “Healthy China 2030” partially, which issued in October 2016 has appealed that students should participate MVPA more than 60min/day and having more than 25% of them achieve an “excellent” rating in fitness.
The results manifested that boys were more physically active than girls, this is similar with previous studies [28, 29].However, the attitude to PA, the most significant contributor to MVPA level in our study, was not different between girls and boys, indicating that the sex difference in MVPA level was from other aspects. Whereas, attitude to PA was a powerful predictor for MVPA level, which has been identified by the previous study that students who think PA is good and engage in PA enjoyable spent more time in MVPA at school[30]. Neighborhood PA facilities were also a significant contributor to student’s MVPA level. This is consistent with other studies that available PA facilities are positively associated with MVPA[17, 31]. In addition, students live in a neighborhood with sport organization and events are more likely to be physically active, which will provide more PA opportunities for children and adolescents. A study from the UK suggested that neighborhood-based PA is critical for helping students to increase MVPA, but not for sedentary behavior reduction [15]. Moreover, active students have active parents, the model effect of parents for their child PA behavior have been identified[32]. In addition, there is a positive relationship between neighborhood PA opportunities availability and parents MVPA days (not shown in result). Maybe there is a mutually promoting relationship, but this is not the scope of this study. Clearly, both the neighborhood PA environment and parents PA behavior associated with students MVPA level significantly. Therefore, neighborhood-based activity may be an effective measurement to increase student’s MVPA out of school. As for the school factors, the results demonstrated that school PA culture/environment associated students physically active significantly, but school PA facilities and PE classes were not. A possible reason may be that these two factors were similar among different schools, as a unique request for the number of PE class and the infrastructures of PA, such as basketball and football court. Besides this, a systematic review has found that facilities and equipment are considered important for physical activity promotion, if the wider school policies do not encourage and support the use of these by all students, the overall impact on physical activity is likely to be negligible[12]. Therefore, a good school PA culture may be more important than physical environment. However, we have not found the promoting role of friends in MVPA level, neither encourage nor accompany. This finding differs from previous studies that friend's encouragement and engagement were positively associated with MVPA [20], but a recent study found that the relationship between friends support and MVPA mediated by self-efficacy and enjoyment[33]. This may indicate that the difference of MVPA level in school-aged children may from family rather than school by bringing together of these evidences. Overall, it appears to be the combination and interaction of school and neighborhood factors that influence adolescent physical activity, rather than a single characteristic of the school or neighborhood.
In the longitudinal model, we found that the students MVPA days will more likely to decrease the MVPA level with age. This is consistent with a meta-analysis of cohort studies[34], it is also the a global issue that cause many health problem. Noticeably, student’s attitude to PA not only associated with a higher MVPA level but also indicate the positive change of MVPA behavior, a previous study supported this result [35]. This can also be explained by autonomous motivation, a component of Self-determination theory(SDT)[36], that autonomously motivation positively predict PA participation[37, 38]. In addition, higher PE motivation associated with PA and sport participation positively[39], which can be explained by the trans-contextual model of motivation, this also the reason why PE class and extra PA time was the potential factors for maintaining and promoting MVPA level[40]. Interestingly, we found that girls are more likely to increase their MVPA level in 12-month follow-up than boys, which consistent with previous a systematic review that non-organized PA declined among adolescent boys but girls[41]. Moreover, basing on the relatively lower MVPA level among girls at baseline, a higher possibility will happen in increasing MVPA level among girls. Finally, compared to a negative change in the MVPA level, students with physically active parents had a trend to remain a stable MVPA level and positively developed their MVPA level with more friend support. Both cross-sectional and longitudinal studies have identified the positive effect of parents and friends on students’ PA behavior[42, 43], and our results strengthen this evidences.
Our study has some obvious weaknesses. First, we assess the MVPA level by self-report, which will cause bias of MVPA assessment and we cannot distinguish the school-day and after-school MVPA by this method. Moreover, we used the days of students participating in MVPA for more than 60 min, as many students cannot estimate the precise duration of MVPA behavior and they cannot distinguish the low-intensity physical activity, moderate-intensity physical activity, and vigorous-intensity physical activity clearly. Therefore, many students did not fill this question. This may cover some information due to the lower precision. Future, more studies need to develop an accurate and efficient tool for students especially for lower age student to estimate the PA time in large scale investigation. Second, we measure the school and neighborhood PA environment by self-perceived instead of the objective assessment instruments, this may limit the implementation of environmental improvement. Future studies should apply the objective assessment instrument to examine the association between these influential factors and MVPA in detail. Consequently, we can understand the association between different influential factors and the distribution of aera and time of PA behavior. In addition, more studies need to explore the transformation of influential factors of PA behavior with age, this will be more effective for precise intervention for PA behavior.
Findings from our study provide epidemiological evidence for children and adolescents MVPA intervention in the future. Moreover, this evidence is also important for developing policies for promoting school-aged children MVPA participating. In our results, improvement of neighborhood PA environment and attitude can’t translate to MVPA level evaluating, indicated that there are some influential factors impacted MVPA of school-aged children significantly with age and school grade increasing. A study from China has reviewed the role of policy to prevent fitness decreasing, and revealed that the policy alone did not seem to work[44]. Therefore, a single health policy can’t improve the MVPA level of school-aged children. In China, the study is the top priority for school-aged children, result that most of their time is used in the study rather than PA. In the future, concurrent education and health policy may be effective for increasing MVPA level of school-aged children. Furthermore, change of behavior is not an isolated problem, as it influenced by many factors and from a distinct level[21, 22]. Future studies should explore influential factors more comprehensively, and the intervention should be full-scale and multilevel.