A mother's exercise habits can have a strong effect on the fitness levels of their children.

Researchers looked at the physical activity levels of 500 mothers and their preschoolers and found a close association between the mother's and children's activity levels, a University of Cambridge news release reported.

The team found that only 30 percent of mothers engaged in at least 30 minutes of moderate-to-vigorous physical activity at least once a week. The study is the first to show that children are not "naturally active" and that parents have a strong impact on their activity levels.

"It is well established that physical activity is closely linked to health and disease prevention. Research shows that active mothers appear to have active school-aged children, who are in turn more likely than their less active peers to have good health outcomes," the news release reported.

In the study the researchers found factors such as if a father was present, the number of children in the home, and maternal education were important factors in the mother's activity level.  The mother's career status also had a major effect.

The researchers fitted both the mothers and children with activity monitors and recorder their exercise habits for about a week.

"We used an activity monitor that was attached to participants and worn continuously, even during sleep and water-based activity," Doctor Esther van Sluijs at the MRC Epidemiology Unit and the Centre for Diet and Activity Research, University of Cambridge, said in the news release. "This approach allowed us to capture accurately both mothers' and children's physical activity levels for the whole of the measurement period, matching hour for hour maternal-child activity levels. This comparison provided us with detailed information about how the association between mothers and children's activity changed throughout the day, and how factors such as childcare attendance and maternal education influenced this relationship."

The team then compared the activity data of the mothers and children.

"We saw a direct, positive association between physical activity in children and their mothers - the more activity a mother did, the more active her child. Although it is not possible to tell from this study whether active children were making their mothers run around after them, it is likely that activity in one of the pair influences activity in the other," Kathryn Hesketh, formerly of Cambridge and now UCL, said in the news release.

The findings suggest that for every minute of moderate-to-vigorous activity a mother participated in , her child was likely to participated in 10 percent more of the same activity.

"Our study shows that the relationship between mother and child activity is moderated by demographic and time factors - for example, for moderate-to-vigorous activity, the relationship was stronger for mothers who left school aged 16 compared to those who left aged 18 or more. The association also differed by time of week, with light activity, such as walking, most strongly associated at weekends than on weekdays. The opposite was observed for moderate-to-vigorous activity which was more strongly associated on weekdays," van Sluijs said.