While there's a rise in childhood obesity, a new study has found that preschoolers don't indulge in much of activity, even when they're playing outside.

The study, by an interdisciplinary team of researchers at the University of South Carolina (USC), Michigan State University, and East Carolina University, looked at 3-, 4-, and 5-year olds enrolled in 24 community-based preschool programs.

Led by Professor Russell R. Pate (at USC), the researchers used information from the Children's Activity and Movement in Preschools Study (CHAMPS).

It was found that the preschoolers were inactive for much of their preschool day, with 89 percent of physical activity characterized as sedentary.

In fact, 56 percent of their activities were sedentary, even when they played outside, a time when children are expected to move around.

To top it all, teachers very rarely encouraged the children to be physically active.

However, when balls and other items were made available, especially outside, and when they had open spaces in which to play, the children were more likely to be active.

"The low levels of children's activity and the lack of adult encouragement point to a need for teachers to organize, model, and encourage physical activity," said William H. Brown, professor in the College of Education at USC and the study's lead author.

He added: "Because children's health and physical well-being are an important part of development, their physical activity needs to be increased in order to promote healthy lifestyles, particularly for preschoolers who are growing up in low-income families and who are at greater risk for poor health outcomes."