Mothers of young children may feel like they don't have much time to exercise, but the more active the moms are, the more active the children.

The activity level of young children is directly linked to that of their mothers, researchers in the United Kingdom say.

But the problem is that mothers with young children aren't very active, says Esther van Sluijs, a behavioral epidemiologist at the University of Cambridge and the study's lead author.

When researchers used accelerometers to track the physical activity of 554 mothers and their 4-year-olds, the mothers on average spent only 19 minutes of their waking hours each day doing moderate to vigorous activity. Only half were active for at least 30 minutes on one or more days each week.

The children were more active, with many getting eight hours of light and moderate activity daily. But even then, the preschoolers got only about an hour a day of running and vigorous play.

Mothers' increased physical activity boosted children's moderate and vigorous activity overall, according to results published Monday in the journal Pediatrics.

It's not entirely clear whether it's the mother's activity that influences her child's, or if mothers are more active because they're busy keeping up with a playful child, van Sluijs says. So efforts to promote physical activity should include both mothers and children.

But busy mothers don't have to drop all other priorities to play with their children all day. Van Sluijs says just small changes – walking to the park instead of driving or playing a good game of tag instead of a board game – can make a difference.

"Increasing your physical activity just by a little bit already helps, you don't have to become an athlete." she says. "If you look at [small increases in activity] over a month or a year, that can actually have quite large benefits."

Fathers weren't part of the study, but van Sluijs says that doesn't mean the call for more exercise should single out mothers.

"We do recommend that interventions are not just targeted at mothers and their children," she tells Shots. "They're actually targeted at the family unit because we know that siblings as well play an important role for children's physical activity."

It's not entirely clear whether it's the mother's activity that influences her child's, or if mothers are more active because they're busy keeping up with a playful child, van Sluijs says. So efforts to promote physical activity should include both mothers and children.

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