Children that get plenty of physical activity when they are young, tend to develop strong healthy bones. The benefits can last well into young adulthood.

A new study found that as children age into adolescence their physical activity levels drop, but the advantages of early exercise remain.

“What parents do to make sure kids are active today matters down the road,” said Kathleen Janz, the study’s lead author from the University of Iowa in Iowa City.

“When you accumulate physical activity as a child, you end up with what looks like better bone as an adolescent,” she told Reuters Health.

Participants in the research were part of the Iowa Bone Development Study, an ongoing study of bone health during childhood and young adulthood. The children had been recruited for that study between 1998 and 2002 when they were about five years old.

At ages five, eight, 11, 13, 15 and 17 years old, the 530 participants wore a device called an accelerometer for four or five consecutive days, including one weekend day, to measure their physical activity whenever they were awake.

When the participants were 17 years old, researchers used bone scans to measure the density, strength and brittleness of their bones. They also used pictures from the scans to estimate the precise geometry of the teenagers’ bone shape, a crucial factor in bone strength.

Researchers found what has sadly become the norm for many kids these days:

-       During childhood, less than 6 percent of the girls were highly active and by their late teens, almost all had become inactive.

-       Boys were more active than girls, but also became much less active as teens.

On average, girls went from being active for 46 to 48 minutes a day in early childhood to being active for just 24 minutes a day as 17-year-olds.

Among boys, activity levels fell from 60 to 65 minutes a day at the beginning of the study to an average of 36 minutes a day by the end.

At age 17, both boys and girls who had been the most active throughout their lives had denser bones and better bone shape than other participants their age that had been less active.

Janz acknowledges that it can be difficult to get teens up and moving.

“In an ideal world, children are active and maintain their activity into retirement, but this activity declines dramatically during adolescence, which is ironically a time when bone is most responsive to activity,” she said.

“It is not all that difficult for kids to be active, whereas sometimes getting adolescents to be active can be more difficult. They have different ideas as to how to spend their leisure time,” Janz said.

What kinds of exercise work best for kids to build strong bones? Janz says that running and jumping are great for building strong bones, but any activity is better than none.

The National Osteoporosis Society UK, also offers these five tips for kid’s bone building activities:

-       Team sports such as football or netball are good for getting children involved in fitness at a young age.

-       Skipping works well because it adds some impact to bones. Aim for 50 jumps a day or skipping for five minutes each day.

-       Jogging builds bone in both the hip and spine in younger people.

-       Tennis or badminton are more high-impact and enjoyable sports that build bone density.

-       Dancing and exercising to music are fun ways to boost bone health as well.

Parents hold the key to helping their children develop good exercise habits. These habits can offer benefits throughout their lives. Study after study reveals that kids are more likely to want to participate in and learn about fitness when they see their parents setting a good example.

Sources: Allison Bond MD, http://www.reuters.com/article/2014/06/05/us-kids-exercise-bone-health-idUSKBN0EG1Q820140605

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