Phase-specific coordination variability differentiates motor competence trajectories in children: Insights from the moves-UP project.

Abstract

Poor motor competence can lead to developmental challenges. Some children will benefit from school-based interventions, but those with persistent difficulties, such as Developmental Coordination Disorder (DCD), often require targeted support. Although some variability supports adaptability, excessive variability may indicate motor impairment. This study examined coordination variability in children with different motor competence trajectories in response to a school-based intervention. As part of the Moves-UP project, motor competence was assessed in 100 children at baseline, 3-month, and 7-month follow-up assessments using the Short Form Dragon Challenge. Children with movement difficulties received a school-based motor skills intervention. Forty-five children (17 with suspected DCD, 28 typically developing) completed kinematic walking assessments at 0 and 7 months. Latent class mixed models identified MC trajectory groups. Functional principal component analysis (FPCA) was applied to foot-shank and shank-thigh coordination variability. Three trajectories were identified: typically developing (class 1), improvers (class 2), and non-improvers (class 3). Class 3 showed greater coordination variability than class 1. FPCA indicated greater deviation patterns in class 3, particularly during early stance, stance-to-swing transition, and terminal swing. A class-by-time interaction in foot-shank fPC3 showed that scores increased in class 1 but decreased in class 3. Shank-thigh fPC3 scores also decreased over time, reflecting altered variability distribution. Children with persistently low motor competence showed elevated and phase-specific coordination variability, consistent with DCD-related motor deficits. These findings support the use of FPCA and coordination variability for early identification and monitoring of persistent motor difficulties.