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Kids Gain Bone Mass, Size from Exercise
 
 
  By Michael Smith, North American Correspondent, MedPage Today
Published: October 16, 2010
 
Action Points
 
* Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
 
* Explain to interested parents that for children ages 7 and 8, intensive physical exercise in school leads to increases in bone mass and size.
 
* Note that there was no significance difference in the rate of fracture among children who had the extra exercise and a cohort who had a standard physical education program.
 
TORONTO -- For children ages 7 and 8, intensive physical exercise in school leads to increases in bone mass and size, a Swedish researcher said here.
 
And over the four years since the program was started, there was no significance difference in the rate of fracture among children who had the extra exercise and a cohort who had a standard physical education program, according to Bjarne Lofgren, MD, of Lund University in Malmo, Sweden.
 
Lofgren reported the results of the controlled trial at the annual meeting of the American Society for Bone and Mineral Research.
 
In the study, one school in Malmo had its students exercise 200 minutes a week, which included doing such activities as running, jumping, rope climbing, and playing ball games. Meanwhile, three neighboring schools offered a standard physical education program of 60 minutes a week.
 
All told, 446 boys and 362 girls took the extra exercise and were followed for a total of 2,675 person-years. They were compared with 807 boys and 780 girls in the control group, who were followed for 5,661 person-years.
 
Fracture rates were monitored prospectively, he said, and after four years the rate ratio for broken bones in the intervention group, compared with the control group, was 1.11, with a 95% confidence interval from 0.78 to 1.57.
 
The researchers measured skeletal development, using dual energy x-ray absorptiometry, in a subset of 73 boys and 48 girls in the intervention and 52 boys and 48 girls in the control group, Lofgren reported.
 
They recorded bone mineral content in the lumbar spine, the femoral neck, and trochanter as well as bone width in the third lumbar vertebra and femoral neck.
 
On average, compared with the control group, the intervention group had yearly gains of:
 
* 0.6 standard deviations in bone mineral content at the lumbar spine in both girls and boys (P<0.001 and P<0.05, respectively)
* 0.5 standard deviations in bone mineral content at the trochanter in girls (P<0.01)
* 0.5 standard deviations in width at the femoral neck in girls and 0.3 standard deviations in boys (P<0.05 for both)
* 0.5 standard deviations in width at the third lumbar vertebra in girls (P<0.05)
 
In the long run, Lofgren told MedPage Today, "it's even more important that they will perhaps have greater peak bone mass when they are 25 or 30."
 
The bottom line of the study is that "there is no downside to physical activity" for young children, said Clifford Rosen, MD, of Maine Medical Center in Portland, who moderated a session at which the study was presented.
 
"The concern was that if you over-exercise young prepubertal individuals, you might actually increase the risk of fracture" because of falls and other accidents, Rosen told MedPage Today, adding that several studies have shown exercise increases bone strength in youngsters.
 
But few, he said, have looked at the risk-benefit ratio in children, and it's reassuring that the Swedish study showed no increase in fracture risk.
 
Lofgren did not report external support for the study. He said he had no disclosures.
 
Primary source: American Society for Bone and Mineral Research
Source reference:
Lofgren B, et al "A four years exercise intervention program in pre-pubertal children increases bone mass and bone size but do not affect the fracture risk" ASBMR 2010; Abstract FR0316.
 
 
 
 
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