An environmental–sensorimotor cascade hypothesis: Spatial and mechanical affordances shape segmental trunk control in preterm infants

Abstract

Preterm infants frequently display delayed postural control and segmental instability, yet the environmental mechanisms influencing this neuromechanical development remain poorly understood. Conventional views emphasize intrinsic neuromuscular immaturity, overlooking how daily environments constrain sensorimotor calibration. Drawing from longitudinal observations of moderate-to-late preterm infants, we propose an environmental–sensorimotor cascade hypothesis. This framework posits that spatial and mechanical affordance within infant home containers (e.g., playpens, cribs/cots, and other bounded spaces)—specifically usable play area and surface compliance—may modulate the quality and frequency of postural perturbations, thereby shaping the maturation of segmental trunk control. Limited spatial area restricts center-of-mass excursions and reduces opportunities for anticipatory and reactive adjustments, while excessively firm surfaces may impose lower demands on proprioceptive reweighting. Conversely, moderately compliant surfaces stimulate multi-segment coordination and feedforward stabilization. Over time, these constraints produce distinct trajectories of static, active, and reactive trunk control, influencing upright locomotor milestones. We hypothesize that such affordance-dependent calibration operates through adaptive tuning of trunk muscle synergies and sensory feedback gain. If confirmed, this hypothesis redefines the environment as an active biomechanical teacher, offering new targets for early intervention in preterm infants.