Diversity and regularity in infant crawling with typical development

[Purpose] The purpose of this longitudinal study was to investigate the diversity in infant crawling and examine the quantitative regularity in crawling variations necessary for the acquisition of walking in infants with typical development. [Participants and Methods] Infants with no neurological or orthopedic problems participated in this study. Using Internet Protocol (IP) cameras, crawling was simultaneously filmed from six different angles. Filming was continued until the acquisition of independent walking. The crawling movement in the video was coded. We considered the number of different completed codes as the number of variations and examined the cumulative number during the filming period in each participant. [Results] Nineteen infants completed the study. The pattern of change in the cumulative number of variations with increasing age (in days) varied between cases. Although the cumulative number of crawling variations at the time of acquisition of independent walking was inconsistent, it was negatively correlated with the crawling start age (in days). [Conclusion] Diversity exists in infant crawling. Infants who start crawling at a younger age tend to express more variation, whereas infants who start crawling when older tend to express less variation.