Phase-specific postural adjustments in children and adults during a challenging balance task.

Introduction: Anticipatory postural adjustments (APAs) stabilize the body before voluntary movement. Although present early in life, their refinement continues into adolescence, especially during complex balance tasks. Aim: This study examined developmental differences in APA control between typically developing children (9-12 years) and young adults (19-25 years) during a self-initiated Can Placement Task (CPT). Methods: Thirty children and twenty-two adults performed the CPT while standing on one leg. The task was divided into five phases (quiet stance, stooping, can transfer, straightening up, stabilization). Center of pressure (COP) displacement and velocity in anteroposterior (AP) and mediolateral (ML) directions and vertical ground reaction force (GRF) on the can were measured using dual force platforms. Both discrete outcomes and Statistical Parametric Mapping (SPM) were analyzed. Results: No differences were observed in static balance (Phase I). In dynamic phases, adults showed larger backward COP shifts during stooping, higher normalized COP velocity, and reduced reliance on the can for support compared with children. Children exhibited slower COP adjustments and higher GRF on the can, indicating greater use of external support. SPM revealed group differences mainly during stooping and straightening phases. Adults' faster COP control likely reflects efficient feedforward strategies, while children adopted more conservative, stability-oriented approaches. Conclusion: Children aged 9-12 years can generate APAs but remain less efficient in adapting them to task demands. Phase-specific and SPM analyses revealed subtle developmental differences not evident in static balance. The CPT provides a sensitive framework for assessing postural control and may guide age-appropriate clinical interventions.