Physical activity builds stronger bones
Exercise, particularly high-impact activity, builds stronger bones in
children, even for those who carry genetic variants that predispose them
to bone weakness, according to new research. The scientists say their
findings underscore that genetics does not necessarily equate to
destiny, and reinforce the importance of physical activity as a key
factor to improve the bone health of children in the present and into
we have known for decades that physical activity during childhood builds
up bone and confers lifelong benefits, we did not know whether the
effects of activity depend on genetic risks for bone fragility," said
first author Jonathan A. Mitchell, Ph.D., a pediatric researcher and
Instructor of Pediatrics at The Children's Hospital of Philadelphia
"This study was the first to show that physical activity can
counteract the negative effects of genetic variants that associate with
bone fragility in childhood."
The research appears online in the Journal of Bone and Mineral
The study team, co-led by senior authors Babette S. Zemel, Ph.D., and
Struan F.A. Grant, Ph.D., both from CHOP, analyzed a cohort of 918
children and adolescents, from 5 to 19 years old, all of European
ancestry, who were part of a larger study group, the Bone Mineral
Density in Childhood Study. That national study enrolled healthy U.S.
children at five sites starting in 2002, with follow-up visits lasting
The current researchers used questionnaires in which study
participants estimated their amount and type of physical activity during
childhood. The study team also measured the participants' bone density
and genotyped their DNA for over 60 genetic variants known to be
associated with bone density.
The researchers found that across the board, children had higher bone
density scores if they had higher levels of physical activity. This even
applied to those with a higher genetic risk for bone fragility.
Importantly, the benefits of activity were driven entirely by
high-impact, weight-bearing activity, such as gymnastics and soccer,
which involve sprinting, turning or jumping actions.
The researchers note that replication studies by other groups are
going to be needed to follow up their study, and that other groups
should investigate similar questions in populations other than the
children of European ancestry covered in this analysis.
However, based on their current results, the researchers advise that
pediatricians, schools and child activity programs should encourage
high-impact physical activity for children who are generally healthy.
The current Physical Activity Guidelines issued by the U.S.
Department of Health and Human Services recommend that children and
adolescents accumulate at least 60 minutes of moderate intensity
physical activity every day. "Our data support the activity guidelines
and specifically indicate that more emphasis should be placed on
accumulating high-impact, weight-bearing physical activity for improved
bone health," said Zemel, the director of CHOP's Nutrition and Growth
Laboratory, and a national expert on childhood growth and bone density.