News Release

Exercise can give you strong bones

Reports and Proceedings

New Scientist

A crucial couple of years can make or break your skeleton

A LITTLE exercise would make a big difference to today's children. Many are failing to build up their skeleton during a vital two-year window before puberty, making them much more likely to break bones later in life.

Heather McKay of the University of British Columbia in Vancouver has shown that children have the greatest increase in bone mineral after the growth spurt just before puberty. Children put on over a quarter of their bone mass in this two-year period, she and a colleague found. In girls, it tends to be between age 10 and 12, while in boys it's between 13 and 15.

Now McKay's team, which is following 383 children aged 8 to 13 for three years, has found that even small interventions during this period can make a big difference. The researchers asked half of their volunteers to do a circuit training programme lasting 10 minutes just three times a week. Children in this group have to skip and do box jumps, side-to-side jumps and other high-impact exercises. Other children spend the same amount of time doing stretches and warm-ups.

After a year, the girls doing circuit training had amassed an extra 2 per cent of bone mineral compared with the stretchers. After two years, they were ahead by 5 per cent. The results on boys are still being analysed.

While the results show that exercise clearly pays off, McKay laments that a third of all Canadian children are not active for even 10 minutes a week. We lose a quarter of our bone mass as we age. Whether this seriously weakens our bones largely depends on how much we build them up in childhood. "If we can increase bone mass by 10 per cent by adulthood, we can decrease the incidence of fractures by 50 per cent," says McKay.

Graham Fishburne of the University of Alberta in Edmonton hopes the study will help persuade parents and teachers that physical education is important. "We can make a difference," he says.

But the way physical education is taught in schools may have to change. Children need real physical skills, not just a few games of dodgeball a week. "There's been a huge deterioration," he says, referring to the inactivity caused by computers, television and gaming. "Yes, there have always been bookworms, but they still had to go to the library and carry the books home."

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Author: Alison Motluk

New Scientist issue: 12th January 2002

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