WASHINGTON (AP) - Parents who exercise tend to have children who exercise, but researchers caution that it's not something a parent can count on.

Even though it seems common sense that role-model parents should raise model children, kids still rank fun first. Parental demonstrations of exercise seem to be somewhere down the list of motivators. However, one study indicates children will benefit if even one parent is a good example.

"Fathers who were more active had daughters who were significantly more active," said Kirsten Krahnstoever Davison of Penn State University. Mothers in her study did almost no physical activity, and had no impact on the likelihood that their daughters would be active, she found.

Davison and her colleagues looked at questionnaire responses from 176 central Pennsylvania 9-year-olds and their parents. She presented her data at an October meeting of the North American Association for the study of Obesity in Quebec City.

The questions looked at such factors as whether the parents tried to use their own activities as examples for the children to follow. Parents also were asked whether they provided logistical support, such as taking the children to activities.

The children were surveyed about what they did and how they preferred to spend their time - for instance, whether they would rather be outside playing or inside watching television.

"Fathers who were active, who explicitly used their own behavior to encourage behavior, and who provided logistic support for their daughters' activity had daughters who were significantly more active," the study found. The father's own activity was a bigger factor than transportation and other logistical assistance, it said.

It is possible that fathers are especially good at motivating daughters, but it might also be that mothers simply were setting poor examples. "One of the obvious things for not seeing anything for mothers is that mothers aren't doing anything," Davison said. "They are supposed to list the sports and activities they do, and they can't list anything."

Even when mothers handled the logistics, it didn't seem to raise their effect on girls' participation, Davison said. Moms who showed up but who weren't physically active themselves could be giving their daughters a mixed message, she said.

The study was able to show an association between fathers' and daughters' activity, but was not designed to prove that the daughters were more active because the fathers were. Nonetheless, the results are in line with other studies, and with the experience of experts.

"It makes so much sense that, if kids see active parents, they'll translate that into their lives," said Charles T. Kuntzleman of the University of Michigan, who was not connected to the study. "I tell parents, 'If you are going to do anything in the physical activity domain, you ought to set yourself as a good example."'

Exercise is a special problem for girls, because they lag behind boys in skills and fitness, Kuntzleman said.

However, the evidence of an effect of that good example is weak, Kuntzleman said. And the value of a good example from a parent can be negated by a poor environment for activity, he said.

"If a sports program is punitive, they are not going to do it," Kuntzleman said. A mean coach or a harsh school physical education turns kids away, he said.

Fun is No.1, said Avery Faigenbaum of the University of Massachusetts, Boston. "I don't know if we can start ranking them below enjoyment and fun," he said.

The problem for kids is that fun itself is down the list of activities they feel they need to do, Faigenbaum said: "Play is being replaced by math tutoring, language classes, religious classes ..."

And parents are not providing much of a good example, he said. "As I see the decrease in physical activity among adults, and this growing inactivity among children, I'm not convinced parents really value physical activity," he said.

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