This study investigates the development of predictive and feedback motor control mechanisms in preschool-aged children (ages 4.5 to 7) during a visuomotor interception task. The primary objective is to evaluate age-related changes in upper limb coordination and postural control by comparing typically developing children with peers exhibiting motor difficulties, specifically those at risk for Developmental Coordination Disorder (DCD).
Interceptive actions, such as catching a moving object, impose high demands on the motor control system, requiring rapid integration of sensory information-visual and proprioceptive-alongside anticipatory postural adjustments and online movement corrections. In typically developing children, the capacity to anticipate and adapt to dynamic stimuli improves significantly between the ages of 4.5 and 7. In contrast, children with DCD often display impairments in these areas, which may be associated with deficits in internal modeling, reduced anticipatory postural adjustments (APAs), and delayed sensorimotor integration. To explore these mechanisms in a controlled environment, the study employs a dynamic bimanual interception task that involves stopping a foam circular pendulum moving horizontally along a rod. This setup allows for precise evaluation of motor response timing and quality, encompassing both upper limb kinematics and center of pressure (COP) displacement.
The research is based on a cross-sectional experimental design involving 60 preschool boys aged 4 to 7 years. Participants are evenly divided into three age cohorts and two motor proficiency groups, identified via the standardized Movement Assessment Battery for Children - Second Edition (MABC-2). Children scoring below the 16th percentile are classified as having motor difficulties. During the experiment, each child performs a bimanual interception task requiring them to stop the pendulum at a defined spatial target ("zero point") under two temporal conditions: intercepting the pendulum on its first pass (short interval, approximately 750 milliseconds from release) and on its second pass (long interval, approximately 1500 milliseconds from release). Multiple trials are conducted in each condition.
Upper limb movements are recorded using four high-resolution video cameras (sampling rate 50 Hz) positioned in sagittal and frontal planes. Motion is tracked via reflective markers placed on anatomical landmarks: the radial styloid process (wrist), lateral epicondyle (elbow), and deltoid insertion (shoulder). Postural control is assessed using a CONFORMat® pressure-sensitive platform operating at 100 Hz, which captures center of pressure trajectory and parameters relevant to anticipatory postural activity, including displacement, velocity, and root mean square (RMS) values. System synchronization is ensured through LED light pulses and color-coded timestamps, with an estimated precision of ±8 milliseconds. Video recordings are analyzed using Dartfish software, which is validated for 2D motion analysis, showing strong reliability (validity r ≥ .95; ICC ≥ .91).
Kinematic parameters include the timing of movement initiation relative to pendulum motion, peak velocity and time to peak velocity of the wrist marker, smoothness of the trajectory derived from acceleration profiles, and spatial accuracy of interception measured as angular deviation from the target. Postural variables include total COP path length as an indicator of stability, the range of movement in the anteroposterior and mediolateral directions, and the mean and RMS values of velocity and displacement during anticipatory postural phases.
This integrative approach allows for a detailed analysis of how young children plan, execute, and adapt their movements in real time. By comparing typically developing children with those at risk for motor coordination difficulties, the study aims to contribute to a better understanding of early motor control mechanisms and inform the development of more targeted diagnostic and intervention strategies.
