Investigating the mediating role of internalizing and externalizing problems on physical fitness in children at risk for Developmental Coordination Disorder

Children with Developmental Coordination Disorder (DCD) have poorer fitness and greater internalizing/externalizing problems compared with typically developing (TD) children. The purpose of this study was to examine the potential mediating role of internalizing/externalizing problems on the relationship between children at risk for DCD (DCDr) and physical fitness. Participants (N = 589) included 288 children with DCDr (Mage = 4.9, 67% male) and 301 TD children (Mage = 5.0, 48% male). Motor skills were assessed using the Movement Assessment Battery for Children-2nd edition (DCDr: at or below the 16th percentile, TD: 16th percentile). Parent-reported internalizing/externalizing problems were measured using the Child Behaviour Checklist. Physical fitness was measured using the Bruce protocol maximal treadmill test and a 30-second Wingate test. Tests for indirect (mediation) effects were assessed using the PROCESS v3.5 software macro. Children with DCDr had higher internalizing and externalizing problems (p < 0.001, d = 0.35???0.46) and poorer fitness levels (p < 0.001, hp2 = 0.05???0.09). Internalizing problems mediated fitness performance on both the treadmill and Wingate test; however, externalizing problems showed no mediating effects. Thus, interventions targeting internalizing problems may contribute to improving performance on fitness-based tasks among children with DCDr.