(1) Background: Limited research exists on the pathways through which physical activity influences cognitive development in the early years. This study examined the direct and indirect relationships between physical activity, self-regulation, and cognitive school readiness in preschool children. (2) Method: Participants (n = 56) aged 3-5 years were recruited from the PLAYCE study, Perth, Western Australia. Physical activity was measured using 7-day accelerometry. Self-regulation was measured using the Head Toes Knees and Shoulders task and cognitive school readiness was assessed using the Bracken School Readiness Assessment. Baron and Kenny's method was used for mediation analysis. (3) Results: After adjustment for socio-demographic factors, total physical activity was positively and significantly associated with cognitive school readiness (B = 0.16, SE = 0.07, p ≤ 0.05). Moderate-vigorous physical activity (MVPA) was positively and significantly associated with self-regulation (B = 0.3, SE = 0.13, p ≤ 0.05) and cognitive school readiness score (B = 0.20, SE = 0.09, p ≤ 0.05). Self-regulation was found to be a partial mediator of the relationship between MVPA and cognitive school readiness. (4) Conclusion: These findings highlight the direct and indirect association between preschool children's physical activity, self-regulation, and cognitive school readiness. Further research is needed to determine the causal relationships between young children's physical activity and cognitive development, over time.
Keywords: child development; cognitive development; preschooler; self-regulation; young children.