By age 3, preschoolers have developed the large motor skills enough to participate in organized games and some sports. Many are now capable of throwing a ball overhand–although it demands more concentration than routine activities, like walking and running.
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.