Approximately 6 months after their first steps, toddlers develop a more mature walking style. They keep their feet closer together and move more smoothly, eventually experimenting with short runs. Although children don’t run well until the third year, most are able to move with great efficiency by their second birthdays. This increase in speed brings new challenges for parents and caregivers because children don’t yet know where it’s safe to run and aren’t very good at stopping quickly to avoid running into things.
Shelov, S. P. (Editor-in-Chief). (2004.) Caring for Your Baby and Young Child: Birth to Age 5. The American Association of Pediatrics. Revised edition. New York: Bantam Books.