In our knowledge, this is the first longitudinal study to explore the change of influential factors of student’s MVPA level in school and neighborhood with age in China. Our result demonstrated that there was no significant improvement in MVPA level after a 12-month follow-up. The likelihood of overweight/obesity will increase with age. Boys and children were more likely to be active lifestyles than girls and adolescents at baseline, but the difference was disappeared at follow-up. However, there was a significant increase in student’s attitudes to PA, especially in children. Moreover, the PA environment in neighborhoods was also improved after “Healthy China 2030” issued, reflected by PA facilities and sport clubs/organizations in the neighborhood, but these factors were not translated into MVPA level evaluating. Student’s attitude for PA and their parental PA behavior were the most important factors to predict the MVPA level at both time points in our study. In addition, influential factors in neighborhood and school were changed in follow-up compared to 1 year before.
In the present study, we have not found decreasing in MVPA with time significantly. This is different from the previous study, which found that MVPA decreasing with age in children and adolescent[25–27].Maybe, this is the reason for overweight/obesity increasing after a 12-month follow-up. Nevertheless, 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]. This may be affected by “Healthy China 2030”, which has appealed that students should participate MVPA more than 60 min/day and having more than 25% of them achieve an “excellent” rating in fitness. Accordingly, the health policy may be effective to prevent MVPA from decreasing with age. Nevertheless, those two were cross-sectional design study.
Our results manifested that boys were more physically active than girls, this has been identified by previous studies[28, 29]. Meanwhile, children were more active than adolescents which consistent with many studies that MVPA was decreasing with age[27, 30]. In the current study, this phenomenon can be explained partially by the attitude toward PA that children have a more positive attitude than adolescents, and attitude to PA was a mean contributor for the MVPA level. This has been identified by the previous study, which found that students who think PA is good and engage in PA enjoyable spent more time in MVPA at school[31]. Nevertheless, the role of attitude for MVPA participation needs to be explored more depth. 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, 32]. 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]. Therefore, neighborhood-based activity may be an effective measurement to increase student’s MVPA out of school. As for the school environment, the results demonstrated that school PA climate and teacher support for PA affected MVPA significantly, but school PA facilities and PE classes were not. These results were supported by the previous system review[12]. A possible reason may be that these two factors were similar among different schools, as a unique request for numbers of PE class and the infrastructures of PA, such as basketball and football court, were similar in Chinese primary and middle school. These factors should be considered for future intervention to increase student’s MVPA. Finally, we found students with active parents are more likely to be physically active, which has been identified by a meta-analysis [33]. Yet we have not found the promoting role of friends in MVPA level, neither support 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[34] This may signify that the difference of MVPA level in school-aged children may from family rather than school by bringing together these evidence.
When analyzed the follow-up data, student’s attitude to PA was significantly improved after 12 months compared to 1-year before, but the improvement was not translated into increasing MVPA level of students, which were not significantly different between the surveys in 2016 and 2017. A similar situation also appeared in the other two neighborhood variables, sport facilities, and sport organizations in the neighborhood. According to the ecological model, the policy is the highest-level factor in four domains, which can influence PA through change lower-level variables [21]. As positive predictor for MVPA, student’s attitude to PA and neighborhood environment (sport facilities and sport organizations in the neighborhood) have improved significantly after “Healthy China 2030” issued, partially proved its’ validity as a national health promotion policy. Accordingly, we can infer that there are some influential factors we have not investigated mediated the relationship between attitude, sport facilities, and organizations and MVPA of children [35]. It is likely associated with increased study-load with one year more senior in school, as indicated by the second most significant contributor to MVPA in 2017 survey is extra time for PA/exercise. Combining with friend support as a contributor for MVPA level indicated that children more likely participated in MVPA in school. Moreover, this phenomenon also might explain the sex factor (boys vs girls) and age factor (children vs adolescents) both of which are significant contributors to MVPA level in 2016, are removed from the logistic regression fitting in 2017. In China, every student has to face the stress for entering a higher school, this may explain the phenomenon above.
Our study has some obvious weaknesses. First, we assess the MVPA level by self-report, which will cause bias of MVPA assessment and we can’t distinguish the school-day and after-school MVPA by this method. 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. Third, we can’t build the causal relationship between the evaluation of influential factors and “Healthy China 2030”. Therefore, we should interpret findings carefully due to these limitations. 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 geography 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[36]. 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.