Development of walking in preterm and term infants: age of onset, qualitative features and sensitivity to resonance.

An increasing number of studies have examined the development of walking in preterm infants; however, the results concerning those who had no major neonatal disease were inconclusive. This study was therefore aimed to examine the age of onset, the quality of early walking movement, and the sensitivity to resonant period of the force-driven harmonic oscillator (FDHO) model in preterm infants who had no major neonatal disease and normal term infants. Twenty-nine preterm infants and 29 term infants were prospectively examined for their age of onset of independent walking and were subsequently assessed the qualitative features of walking at 18 months of corrected age using kinematic analysis. Kinematic variables examined included spatio-temporal organization, inter-joint coordination, and inter-limb coordination. The anthropometric data were used to calculate the resonant period. The results demonstrated that the preterm infants attained independent walking at significantly older ages than the term infants when corrected for prematurity. The preterm infants manifested similar walking characteristics, except for shorter stride lengths, at 18 months of corrected age compared with the term infants. Furthermore, the stride periods of both groups were accurately predicted by the resonant period of the FDHO model. We conclude that preterm birth without accompanied major neonatal disease may affect infants' age of onset and spatial organization but not their sensitivity to resonance during the early stage of walking development.