NOTE TO JOURNALISTS: A color photo of female high-school athletes in training is available from Purdue News Service, (765) 494-2096. Ask for the photo called Bone Building/Teegarden.
WEST LAFAYETTE, Ind. -- Add accelerated bone-building to the list of benefits teen-age girls receive by participating in sports.
"High-school girls who are at least moderately active can increase the density of certain bones at a rate unrivaled at any other time in their life," says Dorothy Teegarden, assistant professor of foods and nutrition at Purdue University. "Particularly the hip bone. That can be important, because hip bone fractures are one of the most common fractures among the elderly. An older person can suffer serious injury -- even death -- from breaking a hip bone weakened over time."
Teegarden and fellow researchers measured the mineral content and bone density in young women to determine how previous activity had influenced bone growth. Study participants were 204 minimally active women between the ages of 18 and 31. The women in the study reported their past and present occupations and activity levels.
"In our findings, no other physical activity affected the density of the hip bone, other than athletic activity during the high-school years," Teegarden says. The researchers found that athletic participation during high school increased the mineral content of the hip bone by about 7 percent. Teegarden says women who had participated in high-school sports increased their bone mineral content overall by 5 percent, and the only bone that didn't seem affected by high-school activity was the radius, an arm bone between the wrist and elbow.
The researchers found that even low levels of exercise helped to increase bone mineral content, with the amount of the increase depending on the age at which a woman was active. Teegarden says that based on their study, a woman can increase the density of some of her bones until she reaches age 21. She says bone size -- but not density -- can also increase in a woman until age 26.
Fellow researcher Roseann Lyle, associate professor of health promotion, says the type of physical activity didn't really matter. "We thought that weight-bearing exercise, such as running or playing basketball, would have more of an effect on bones than would sports like biking or swimming, which don't put weight on the bones," she says. "However, in our study, that wasn't the case."
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