Teens Who Are Lazy Bones Have Weaker Skeletons

Inactivity can lead to weaker bones in teens, a new Canadian study finds.

Researchers reviewed physical activity and bone strength in more than 300 teens over a four-year period that is important for healthy bone development -- ages 10 to 14 for girls and ages 12 to 16 for boys.

During those years, up to 36 percent of the skeleton is formed, and bone is particularly responsive to physical activity, the researchers said.

"We found that teens who are less active had weaker bones, and bone strength is critical for preventing fractures," said lead author Leigh Gabel, a Ph.D. candidate in orthopedics at the University of British Columbia.

"Kids who are sitting around are not loading their bones in ways that promote bone strength," which is why teens need to engage in weight-bearing activities such as running and jumping and sports like soccer, ultimate Frisbee and basketball, Gabel said in a university news release.

Teens don't have to do structured or organized sports and activities to boost their bone health. Simple things such as dancing at home, playing tag at the park, chasing the dog or hopping and skipping are also effective, according to the researchers.

Parents and caregivers should limit teens' screen time and be good role models of an active lifestyle, said co-author Heather McKay, a professor at UBC and director of the Centre for Hip Health and Mobility in Vancouver.

The study was published March 22 in the Journal of Bone and Mineral Research.