How much physical activity do you need? It's a question the federal government is trying to answer.

The Health and Human Services Department has released new physical activity guidelines.

Surrounded by Olympians and Parolympians, President George Bush urged average Americans to take a look at the new physical fitness guidelines and get active.

While a little activity may not make an Olympian, the Health and Human Services Department says it can make a big difference in Americans' health.

According to the new guidelines, adults gain substantial benefits from just two and a half hours a week of moderate aerobic activity, like bike riding or brisk walking, or an hour and fifteen minutes of more vigorous activity.

Kids need one hour or more of physical activity a day, including intense activity, three times a week.

The new physical activity guidelines are the most comprehensive of their kind, based on the first government review of scientific research and health in more than a decade.