A280: Physical Activity, Social Support, and Stress Among High School Students, Moderating Effects of Only-Child Status

Stress levels reflect an individual's psycho-physiological imbalance in response to environmental demands. Research suggests that physical activity not only directly alleviates negative emotions but may also indirectly reduce stress levels by enhancing social support networks. However, the underlying mechanisms of this pathway and the moderating effects of family structure differences (e.g., only-child status) are unclear. This study aimed to explore the relationship between physical activity and stress levels among high school students in Shandong Province, test the mediating role of social support between the two, and analyze the moderating effect of only-child status on the relationship. Method: The present study used the Youth Physical Activity Questionnaire, the Quality-of-Life Scale for Children and Adolescents, and the SCL-90 Symptom Self-assessment Scale to survey 9504 senior high school students in Shandong Province. The Cronbach's alpha coefficients of the questionnaires were tested to be above 0.9. Descriptive statistics, independent samples t-test, correlation analysis, mediation effect, and moderated mediation effect tests were used to analyze the data. The mean age of the respondents was 16.5 years, and 47.7% were female. The results found that (1) non-only children had significantly higher levels of stress and social support and lower levels of physical activity than only children (p < 0.01); (2) the level of physical activity was a significant positive predictor of students' social support (β=1.034, p < 0.01), and a significant negative predictor of students' stress levels (β=-0.736, p < 0.01). (3) Considering the mediating role of social support, physical activity had an indirect effect on social competence through mental health status, with a mediating effect value of -0.662 (95% BootCI -0.078, -0.058), and the direct effect of physical activity was not significant after controlling for social support. Thus, social support played a fully mediating role between physical activity and stress levels. And different only child statuses played a moderating role in the relationship between physical activity and social support, and between social support and stress levels. The study suggests that adolescents' level of physical activity has a significant positive impact on their social support and reduced stress levels. In addition, physical activity was a stronger positive predictor of social support among non-children, and their social support had a more significant mitigating effect on stress levels. The results reveal the resourcefulness of a multi-child family structure in adolescent sports socialization.