Ethan Coon was working to develop good posture and strengthen his core muscles, though from all his wiggling and giggling, you would hardly know it.

By the time he hit potty break, the 2-year-old and his classmates had bounced on a mini trampoline, rolled on their bellies on scooters and crawled through mazes.

The children were participating in a class in Highland Park, Ill., that uses preschool playtime to teach good habits in posture and movement and prevent sports-related injuries later in life.

Many doctors agree they are seeing young children with injuries more commonly seen in adults, from torn knee cartilage to lower back pain. About 2.4 million children ages 5 to 18 were treated for sports-related injuries in U.S. emergency rooms in 2000-01, according to a study by the Centers for Disease Control and Prevention, which does not have comparable research to show whether the numbers are rising.

"They're way too young to be having these problems," said kinesiotherapist Marianne Vuckovich, who in her private practice once saw an 11-year-old girl who shattered her tibia after rotating her leg too much during soccer.

Vuckovich, 43, evaluates children before and after her 10-week sessions at the Recreation Center of Highland Park, leading them through dozens of activities that target specific muscles and good posture.

She has taught classes to all age groups for 20 years, refining her techniques with the youngest clients over recent years. Unlike the usual playtime activities aimed toward toddlers, Vuckovich brings a therapeutic approach to children who are developing normally, unlike most kinesiotherapists who focus on children with developmental problems. The course, which consists of weekly one-hour classes, costs $155 for Highland Park residents and $170 for nonresidents.

Other medical experts stressed there is no data that examines the effectiveness of working with children so young.

During a recent class, the 2-year-olds were a blur of motion, heading from one activity to the next in a room that looked to be a kids' paradise, filled with foam blocks, balls, balance beams, scooters and balancing devices.

Vuckovich believes children as young as 2 can learn basic skills such as carrying their weight more evenly and squatting to pick up a toy through the activities, even if they don't know it.

"You have to balance things out," she said.

Ann Coon of Highland Park said she enrolled Ethan in the class after watching how much her daughter enjoyed another Vuckovich class geared for children ages 4 to 6.