The short answer is: the more activity kids get, the better off they will be. But we've also got some guidelines for you to follow with your family as well. In 2008, the U.S. Department of Health and Human Services (HHS) released the Physical Activity Guidelines for Americans, and here are its fitness recommendations for children and adolescents, from ages 6 to 17:

• A total of 60 minutes or more of daily physical activity (keep in mind that children are typically active in short bursts). Most of that should be either moderate- or vigorous-intensity aerobic physical activity, and should include vigorous-intensity physical activity at least three days per week. Examples of aerobic activity include brisk walking, running, hopping, skipping, dancing, bicycling, jumping rope, and swimming.

• As part of their 60 or more minutes of daily physical activity, children and adolescents should include muscle-strengthening physical activity on at least three days of the week. For children, this type of activity may include using playground equipment, climbing trees, or playing tug-of-war. For tweens, examples of this type of activity include lifting relatively heavy objects (talk to your pediatrician to ensure your child is ready for exercise like this) or using body weight for resistance such as with push-ups.

• In addition, kids and adolescents should incorporate bone-strengthening physical activity  (e.g., brisk walking, running, jumping jacks, jumping rope, basketball, tennis, hopscotch, weight training for tweens with a doctor's approval) into their hour or more of daily physical activity, at least three times per week.

Now you must be thinking, those recommendations are for kids ages 6 and older. How much activity should my preschoolder or younger child get? Don't despair, The National Association for Sport & Physical Education (NASPE), offers these guidelines for you:

• Toddlers (12 to 36 months old) should accumulate at least 30 minutes daily of structured physical activity; preschoolers (3 to 5 years), at least 60 minutes -- and in a variety of activities and settings.

• Toddlers and preschoolers should engage in at least 60 minutes and up to several hours per day of daily, unstructured physical activity and should not be sedentary for more than 60 minutes at a time, except when sleeping.

And if those are too many numbers to keep straight, consider the American Academy of Pediatrics' (AAP) advice to simply encourage free play in young children. For those ages 4 to 6, stimulate them with activities such as running, swimming, tumbling, throwing, and catching. The AAP says to focus on fun, playfulness, exploration, and experimentation while offering supervision and limited instruction (e.g. using a show-and-tell style). As for toddlers, stroll with them through a park, zoo, or your neighborhood, and let their curiosity move them, literally, while providing them with a safe environment to enjoy themselves and master basic motor skills.