The Mediating Effect of Physical Fitness on the Relationship Between Developmental Coordination Disorder and Physical Activity in School-Aged Children—An Observational Study

Evidence remains limited on the interconnections between developmental coordination disorder (DCD), health-related physical fitness—including body composition, flexibility, strength of lower body, and cardiorespiratory fitness—and objectively measured physical activity (PA) in school-aged children. This study aimed to (1) examine differences in physical fitness and PA between children with and without DCD and (2) investigate whether physical fitness functions as a mediator in the association between DCD and PA in school-aged children. Sixty-three children aged 6.5–8 years (12 DCD, 19.05%) who provided valid data were enrolled. Mediation analysis was conducted using the PROCESS macro for SPSS. Flexibility significantly mediates the relationship of DCD to vigorous PA (VPA) (effect = 3.202, bootstrap SE = 1.682, 95% bootstrap CI = 0.463, 7.078), as well as DCD to moderate-to-vigorous (MVPA) (effect = 5.194, bootstrap SE = 2.903, 95% bootstrap CI = 0.434, 11.778). Additionally, there was a significant mediating effect of lower muscle strength on the relationship between DCD and VPA (effect = −1.943, bootstrap SE = 1.297, 95% bootstrap CI = −5.112, −0.021), and DCD and counts per minute (CPM) in axis 2 (effect = −34.388, bootstrap SE = 20.212, 95% bootstrap CI = −80.819, −1.353). The findings highlight flexibility and lower-body strength as potential mechanisms underlying the association between DCD and PA participation. These factors may represent candidate intervention targets; however, their roles require confirmation in larger samples and longitudinal designs.