Inactive teens risk lower bone strength

Inactivity is causing a lack of bone strength in vital teen developmental years, according to latest research. 

Despite boys having larger and stronger bones when compared to girls, the research found boys who spent more time on the couch than running, jumping or playing sports had lower bone strength to those who were active on a regular basis.

Researchers from the University of British Columbia in Canada studied a group of teens over the key four-year developmental/pubescent period (10-14 for girls and 12-16 for boys), finding a gap between those who participated in 60 minutes of moderate to vigorous physical activities daily and those who got less than 30 minutes per day.

Lead author Leigh Gabel said the study found teens that were generally less active had weaker bones.

“Bone strength is critical for preventing fractures,” Ms Gabel said.

“Kids who are sitting around are not loading their bones in ways that promote bone strength,” she said.

She said the four year window studied by researchers was critical for teen bone development, when more than 30 per cent of the human skeleton was formed and bone was particularly responsive to physical activity.

A 2014 longitudinal study of bone health among teens by the University of Iowa had similar outcomes; finding as teens aged their physical activity levels diminished which impacted on their overall bone strength.

Participants in the study were tracked from 5-17 years of age, with researchers measuring physical activity levels and bone strength, density and size at certain intervals as the group aged.

Researchers found that during childhood less than six per cent of girls were highly active on average and by their late teens most had become completely inactive.

Boys also generally became less active as they developed – but did get more exercise on a daily basis in comparison to girls participating in the study.

Boys nearly halved their rate of activity level by the end of the study, with five year olds measuring about 60-65 minutes per day and those at 17 clocking only 36 minutes on average per day.

Researchers also found that the children who were most active throughout their childhood and the study had the strongest, most dense bones at the completion of the 12-year study period.

As a result, they recommended parents encouraged lots of physical activity in childhood to maximize bone strength in adolescent years when activity tapered and beyond to adulthood.

University of British Columbia researcher Ms Gabel said the challenge of getting teens up and moving was not difficult. Physical activity undertaken by teens to meet daily requirements did not have to come in the form of structured activity and short bursts of activity added up to meet daily requirements – dancing at home, walking the dog, playing a game with friends in the park – all constituted activities which added to strengthening their bones.

“The bottom line is that children and youth need to step away from the couch and move to build the foundation for lifelong bone health,” she added.