Want your kids to get more exercise when they go to the park? Don’t go with them.

A study published in the September issue of the American Journal of Preventive Medicine looks at the way kids use parks for physical activity. The study, which documents the activities of 2,712 children (most of them age 12 and under) at 20 parks in Durham, N.C., offers observations that might prove useful to people who design parks or promote their use for health.

According to the study, girls were seen to be less active than boys, and the highest levels of activity were observed in parks featuring basketball courts. Kids also tended to be most active when surrounded by lots of other active kids.

The headline-grabbing finding, though, was that the single most potent factor associated with how much physical activity kids (especially little ones) got was the presence of a parent: Kids with a parent in the park engaged in far less physical activity than those whose parents weren’t there. (Non-parental caregivers had a similar, but lesser, influence.)

The study says this is in keeping with other research showing that parents’ worries about their kids’ safety hampers outdoor play. The dwindling amount of outdoor play among U.S. children is thought to contribute to childhood obesity in this nation. Creating safe access to parks and playgrounds could help turn that problem around.

The authors suggest that, in park settings, landscaping and design decisions could create play spaces that would leave room for children to run free while allowing their parents to keep an eye on them -- without undue hovering.

The authors, of course, don’t advise sending kids to the park on their own. But maybe if we parents could manage to back off a bit and let our kids play on their own, they’d burn off a few extra calories. And, oh, maybe they’d even have some extra fun.