Does perceived motor competence and health-related physical fitness mediate the relationship between actual motor competence and physical activity in middle and late childhood?

Background: Limited evidence exists regarding the mediating roles of perceived motor competence (PMC) and health-related physical fitness in the relationship between actual motor competence (AMC) and moderate-to-vigorous physical activity (MVPA), particularly across middle and late childhood. Objectives: This cross-sectional study examined whether PMC and health-related physical fitness mediate the AMC-MVPA relationship in children across middle and late childhood, while exploring differences between these two developmental periods. Methods: A total of 578 Chinese children, comprising 273 children in middle childhood (mean age = 8.4 ± 0.52 years; 52.3% girls) and 305 in late childhood (mean age = 11.6 ± 0.68 years; 50.5% girls), participated in this study. AMC was evaluated using the Test of Gross Motor Development-3, PMC was assessed with the Pictorial Scale of Perceived Competence and Social Acceptance and the Self-Perception Profile for Children, MVPA was measured via accelerometers, and health-related physical fitness was determined through body mass index, vital capacity, 50-m dash, sit-and-reach test, and 1-min rope-skipping test. Data were analyzed using structural equation modeling. Results: For middle childhood (6-9 years), AMC showed direct effects on PMC (β = 0.43, Conclusion: The mediating pathways linking AMC to MVPA demonstrate a distinct developmental shift. Health-related physical fitness serves as a prominent mediator in middle childhood, yet its influence attenuates in late childhood. In contrast, PMC maintains a stable mediational role across both periods. Interventions designed to promote PA via motor competence must be developmentally tailored: prioritizing fitness enhancement in middle childhood and shifting focus to address evolving psychosocial barriers in later years.