Analysis of centre of pressure trajectories and plantar pressure distribution to map development of foot-ground interactions from new to confident walking infants.

Independent walking is a crucial milestone, allowing infants to explore their environment efficiently. This phase introduces complex foot-ground interactions. However, previous studies have focused on either center of pressure (CoP) or plantar pressure distribution alone, often losing critical information. The impact of variables like body weight, height, and foot size on pressure distribution in infants remains also underexplored. Our study uses continuous statistical approaches to comprehensively analyze anterior-posterior (AP) and medio-lateral (ML) trajectories of CoP and plantar pressure distribution in infancy, mapping foot-ground interactions from new to confident walking stages. Thirty-nine infants walked across an EMED xl platform as new and then confident walkers. Frames of pressure steps were exported and processed in Matlab 2019b. Upon data normality assessment, AP and ML trajectories of new and confident walking steps were compared with parametric two-sample paired SPM1d t-test. Plantar pressure distribution between new and confident walking were compared using the nonparametric two-sample paired SPM1d t-test. Nonparametric linear regression analysis at pixel-level considered variables like body weight, height, foot dimensions, and walking experience, ensuring only non-correlated items were included. Our analyses revealed significant changes in CoP and plantar pressure distribution from new to confident walkers. New walkers initially contact the ground with the central part of their foot, while confident walkers show a more posterior initial contact. Confident walkers also exhibit more medial heel contact and a progression of CoP trajectories closer to the foot's longitudinal axis. Regression analysis indicated that increasing walking experience significantly predicts higher pressure in the lateral and central forefoot. These findings underscore the importance of combining multi-segment joint analysis with plantar pressure data to fully understand foot development during infancy. This project highlighted key aspects of the unique biomechanics of infants' foot development, emphasizing the need for further research to enhance understanding and inform clinical practices.