One-quarter of preteens exercise only at school, study finds

? America’s children are even more deeply rooted couch potatoes than experts initially thought.

Roughly three out of five children ages 9 to 13 report that they don’t participate in sports or other coached physical activities outside school, according to a first-of-its-kind nationwide survey of children and their parents to be released today by the Centers for Disease Control and Prevention in Atlanta.

About one in four children in that age group had gotten no exercise at all outside school in the previous week.

Health experts said the inactivity was greater than they had expected and was worrisome. Lack of exercise is a likely contributor to the dramatic increases in obesity and type II diabetes among American children.

“This whole sedentary lifestyle is a big cultural problem in our country, and that’s what we’re up against,” CDC health scientist Marian Huhman, the lead author in the study, to be published in today’s Morbidity and Mortality Weekly Report, said Thursday.

The 9-to-13 age is key because that’s the most physically active period of most people’s lives, Huhman said. It’s also the age when changes in exercise habits probably would do the most good.

Once children hit puberty, “they become physically less active,” said Ruth Saunders, a professor of health promotion at the University of South Carolina’s school of public health in Columbia. “If you start with only a third of them reporting being active in some structured way at age 13 by the time they finish high school who is going to be active?”