Pengfei Ji, Yongxin Wang, Jirui Qiu, Yansong Li, Xue Xia
(1) Background: Rumination is closely associated with adolescent social interaction anxiety, and physical activity has been linked to both repetitive negative thinking and anxiety-related symptoms. This study examined the network relationships between different dimensions of rumination and social interaction anxiety and explored the moderating role of physical activity level. (2) Methods: A total of 1194 adolescents aged 14-18 years (525 boys, 669 girls; M = 16.27, SD = 0.80) completed measures of rumination, social interaction anxiety, and physical activity. A moderated network model was estimated using the modnets package in R, and bootstrap procedures were used to assess network accuracy and stability. (3) Results: All rumination dimensions were positively connected, with the strongest association between symptom rumination and reflective pondering. Brooding showed the largest conditional association with social interaction anxiety among the three rumination dimensions and the highest expected influence. At higher physical activity levels, the estimated positive conditional association between symptom rumination and brooding was weaker, the association between reflective pondering and brooding was stronger, and the association between brooding and social interaction anxiety was weaker. (4) Conclusions: In the estimated network, brooding showed the highest expected influence and the largest conditional association with social interaction anxiety among the three rumination dimensions. Several estimated conditional associations involving brooding differed across physical activity levels. However, given the cross-sectional design and the limited stability of the interaction estimates, these moderation patterns should be regarded as exploratory. They reflect correlational differences in the estimated network across physical activity levels rather than evidence of a protective effect of physical activity.