WASHINGTON (AP) - Getting babies to be active isn't rocket science: Put a 3-month-old briefly on his tummy and watch him struggle to lift his head. Move an infant's hands to play patty-cake. Provide crawlers with sturdy furniture to pull on and soon they'll stand.

But too many tots are confined for long periods in strollers, baby seats or playpens when they should be moving around, says the National Association for Sport and Physical Activity.

Instead, babies, toddlers and preschoolers need simple but targeted daily activities that are crucial building blocks in learning to walk, run and eventually do all the other tasks the rest of us take for granted, the association says in new guidelines for children under 5.

The nonprofit group, known for exercise guidelines for older children and adults, aimed its latest recommendation at helping parents, day care centers and preschools help tots develop motor skills.

Many parents assume skills such as rolling, sitting and walking will just come naturally as babies grow, said guideline co-author Jane Clark, a movement specialist at the University of Maryland.

But "you have to provide that environment that hooks the brain up to the muscles," she said.

"We 'containerize' kids" to keep them safe while parents are busy, added Michigan State University exercise physiologist Jim Pivarnik, a co-author of the guidelines. Give them a safe environment and "let them out, let them explore, let them move."

Nobody's suggesting baby gym class. The goal is commonsense, fun activities - and making physical activity part of normal, everyday life in hopes that the children will not grow up to be among the 60 percent of Americans who are overweight.

For example, an infant who spends much of the day in a bouncy seat may like watching the suspended toys but probably will roll over or sit later than babies who spent more time stretching out on a blanket.

Watch a 2-year-old throw. It's inevitably overhand, and they step forward on the same side as the throwing arm. If the parents do not like throwing balls around, the tots will not progress as quickly to the next step - throwing in more of a baseball stance - as their peers, Clark said.

One solution is using soft balls that will not break anything. They do not have to be special or expensive. Clark advised making a ball with old pantyhose or wadded newspaper and a little tape.

Because young children naturally move around a lot, many caregivers assume they are getting all the physical activity they need. But TV and video games keep a lot of preschoolers sedentary for longer than parents may realize, said Dr. Nazrat Mirza of Children's National Medical Center. In inner cities, youngsters often have few safe playgrounds or bike paths.

Plus, different activities are needed at different ages to spur development, Clark added.

Among the guidelines:

-Part of an infant's day should be spent in structured activity with a parent or caregiver - playing peekaboo or patty-cake, being carried to and exploring new environments.

-Do not keep infants or toddlers in baby seats or other restrictive settings for long periods. Even young infants move differently when placed on a blanket on the floor than when in a baby seat.

-Toddlers should accumulate at least 30 minutes of structured physical activity, and preschoolers at least an hour, each day. Play follow-along songs, chase or ball; for older children, balancing games or tumbling increase strength and body control.

-Toddlers and preschoolers should spend at least an hour, preferably more, a day in free play - exploring, experimenting, imitating. Caregivers should provide safe objects to ride, push, pull, balance on and climb.

-Toddlers and preschoolers should not be sedentary for more than an hour at a time except when sleeping.

Physical activity should not be forced or used as punishment, the guidelines say. Instead, it should be a routine part of daily life - and parents should join in, not just sit on a park bench and watch the children romp.

Copyright 2002 The Associated Press. All rights reserved.