Background and purpose: Study of kicking development provides important information to understand how early spontaneous movements change in infants as they acquire voluntary control. Researchers have investigated the kicking movements of preterm infants; however, the movement patterns that they have described were inconsistent. The purpose of this study, therefore, was to examine the development of kicking movements with kinematic analysis in preterm infants with very low birth weight (VLBW) and full-term infants.
Subjects and methods: Twenty-two infants with VLBW who were divided into low gestational age (gestational age of <30 weeks, n=9) and high gestational age (gestational age of >or=30 weeks, n=13) classes and 22 full-term infants were evaluated during kicking movements using 4 synchronized cameras and 3-dimensional kinematic analysis when the infants were 2 and 4 months of corrected age.
Results: The infants with VLBW and a high gestational age showed similar kicking movements compared with the full-term infants. In contrast, the infants with VLBW and a low gestational age exhibited a higher kick frequency and a shorter flexion phase at 4 months of corrected age. They also exhibited a higher hip-knee correlation and lower variability in the interlimb coordination pattern at 2 and 4 months of corrected age.
Discussion and conclusion: The findings indicate that infants with VLBW, particularly those with a low gestational age, have age-related differences in movement organization and coordination of kicking compared with full-term infants.