Infants should be free and encouraged to move whenever possible. All that arm swinging and leg kicking is great. Although formal infant exercise programs are available, there is no evidence that they provide any benefit beyond the opportunity for baby-parent interaction. This you can do on your own, any time. In toddlers, the transition from crawling to standing and walking is a natural and normal part of growing and experiencing movement.
Preschoolers explore a broader range of movement as they learn to run, jump, climb, and throw.
Informal and friendly play will do much to nurture their love of physical activity. School-age children enjoy the challenge of more formal games and activities. Basic coordination is well developed by about age 7. At age 8, children are playing more games than at any other time. We should take advantage of this natural inclination.