Everyday Vigorous Activity Increases Bone Strength in Children

Main Category: Pediatrics / Children's Health
Article Date: 15 May 2005 - 10:00 PDT

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Young children who engage in 40 minutes of normal vigorous activity each day have significantly stronger bones than their less active peers, according to new research presented in the July issue of Medicine & Science in Sports & Exercise®, the official scientific journal of the American College of Sports Medicine (ACSM). Researchers say the results indicate activity during childhood, when bone is most likely to adapt and adjust to the strains of physical activity, may have as much influence on osteoporosis prevention as adult interventions.

"It is important that children not miss this critical window of opportunity for building strong bones," said Kathleen F. Janz, Ed.D., FACSM, the study's lead author. "The process of creating healthy bones begins early. We should encourage children to get outside and play and engage in vigorous, high-intensity, muscle-flexing activities."

To study the relationship between childhood activity and bone health, Janz and her colleagues recruited more than 460 children averaging five years of age. They surveyed parents to ask about each child's daily activity level, then had each child wear a device that recorded the amount and intensity of activity, minute-by-minute. Each child wore the device for four days, including one weekend day. Activity levels found for each child were compared to clinical measurements of bone size and strength taken at three locations at and around the hip. The bone measurements were taken using the same instrument used by doctors to diagnose osteoporosis in older adults.

At each bone measurement site, children who accumulated the most vigorous activity had significantly greater measurements of bone area and strength. These children performed an average of 42 minutes or more of high-intensity activities like hopping, running and jumping per day. On average, boys who accumulated the most vigorous daily activity had nine percent more bone area and 12 percent more bone strength than less active boys. The most active girls had seven percent more bone area than less active girls, and nine percent more bone strength.

Because of the location of bone measurements taken around the hip, the research suggests that the increases in bone quality are due to bone's natural ability to adapt to physical activity. The hip is the part of the skeleton that most depends on physical activity to stay strong. It is also the site of osteoporotic fractures that are the most life-threatening and debilitating.

The researchers also found that boys and girls took part in similar amounts of moderate daily activity, but that boys accumulated about 10 minutes more daily vigorous activity than girls. The boys in the study had significantly stronger bones than their female peers.

"Many people, understandably, believe that all children at this age are active enough to get the exercise they need for healthy bone development," said Janz. "Our work suggests otherwise, especially in the case of young girls. Later in life, for a multitude of reasons, girls will have less bone to lose, and as older women will be much more likely to suffer from osteoporosis than men. The best way to promote activity is to let kids be kids by allowing them to play and enjoy activities that require jumping, tumbling, and running."

The American College of Sports Medicine is the largest sports medicine and exercise science organization in the world. More than 20,000 international, national, and regional members are dedicated to advancing and integrating scientific research to provide educational and practical applications of exercise science and sports medicine.

NOTE: Medicine & Science in Sports & Exercise® is the official journal of the American College of Sports Medicine, and is available from Lippincott Williams & Wilkins at 1-800-638-6423. For a complete copy of the research paper (Vol. 37, No. 5, pages 832-837) or to speak with a leading sports medicine expert on the topic, contact the Department of Communications and Public Information at 317-637-9200 ext. 127 or 117. Visit ACSM online at http://www.acsm.org.

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