Associations of Physical Activity with Age of Attaining of Gross Motor Milestones in Full-term and Preterm Infants during Early Infancy

This study aimed to compare the physical activities of full-term and preterm infants at 2 and 4 months corrected age, and to examine the relationship between physical activities and the age at which specific milestones (rolling, crawling, and sitting) were achieved.

Ten full-term and 14 low-risk preterm infants participated in this study. Physical activity data at 2 and 4 months corrected age (CA) were collected using accelerometers (ActiGraph wGT3X-BT^®) randomly placed on one side of the wrist (upper extremity) and ankle (lower extremity) for 24 hours. The study analyzed the amount of physical activity and the percentage of time spent in moderate-to-vigorous activity for the upper extremity, lower extremity, and the combined total during waking hours. Additionally, monthly phone calls were made to parents to gather information on the age at which specific milestones were achieved, which was validated through video recordings of the infants. 

Preterm and full-term infants showed no significant differences in any physical activity measure and age of attaining specific milestone. Both groups exhibited significantly higher lower extremity activity at 4 months CA compared to 2 months CA, while no age-related differences were observed in other measures. Additionally, higher upper and lower extremity activity at 2 months CA, and higher lower extremity activity at 4 months CA, were each significantly associated with earlier attainment of rolling. Similarly, higher upper extremity activity and a greater percentage of time spent in moderate-to-vigorous activity at 2 months CA were significantly linked to earlier attainment of sitting. Age of attaining crawling, however, was not correlated with any physical activity measure.

Full-term and low-risk preterm infants had comparable physical activities at 2 and 4 months CA and both groups revealed an increase in lower extremity activity from 2 to 4 months CA. Furthermore, physical activities of full-term and low-risk preterm infants during early months of life were significantly associated with age of attaining of rolling and sitting.

Monitoring physical activity in infants during early postnatal period may provide important information concerning gross motor development during early infancy. Inclusion of high-risk infants for future study is required.