Environmental mechanics shape segmental trunk control in moderate-to-late preterm infants: A longitudinal analysis...

Segmental trunk control is central to upright motor development in preterm infants, yet evidence linking specific home environment attributes to condition-specific control in late infancy remains limited. This study aims to examine the associations between characteristics of commercial baby containers-defined as restricting equipment or furniture such as playpens and cots-and segmental trunk control during the standing-walking window. Additionally, age-related usage patterns of these containers from 8 to 13 months corrected age were described. In a prospective longitudinal study of 76 moderate-to-late preterm infants, caregivers provided monthly reports on container usage, specifically categorizing attributes of size, rail height, and floor surface compliance. Segmental trunk control was assessed monthly using the Segmental Assessment of Trunk Control (SATCo) under static, active, and reactive conditions. Results indicated that trunk control improved with age across all conditions, although reactive control initially developed more slowly than static and active control before converging at full proficiency by 13 months. Larger container size was consistently linked to better trunk control across static, active, and reactive conditions. Floor surface compliance also played a significant role; soft floors were associated with better static and active control but did not influence reactive control. Conversely, the height of the container rails showed no independent relationship with trunk control performance. Usage patterns shifted over time toward larger spaces and firmer surfaces. These findings suggest that in late infancy, expanded physical space consistently supports segmental trunk control, while surface compliance specifically benefits steady-state and anticipatory control. The results support low-cost, home-based guidance that encourages expanding safe play areas and selecting appropriately compliant surfaces to foster motor development in preterm infants.