TUESDAY, April 5 (HealthDay News) -- Girls involved in high-impact activities such as running, basketball, gymnastics and cheerleading are at increased risk for stress fractures, a new study finds.

Researchers analyzed seven years of data involving 6,831 girls, aged 9 to 15, in the United States. During that time, 267 (3.9 percent) of the girls developed a stress fracture.

Girls with a family history of osteoporosis or lone bone-mass density had nearly twice the increased risk of suffering a stress fracture than other girls. The researchers also found that girls who did eight or more hours of physical activity a week were twice as likely to develop a stress fracture compared to girls who did less than four hours of physical activity a week.

When the researchers focused on high-impact activities, they found that only basketball, running, gymnastics and cheerleading were independently associated with a greater likelihood of stress fracture. Each hour per week of participation in these activities increased the risk of stress fracture by about 8 percent.

The study also found that girls who started menstruation at a later age were more likely to suffer a stress factor. Each one-year delay in the start of menstruation was linked with about a 30 percent increased risk.

There was no association between stress fracture risk and being overweight, underweight or having an eating disorder.

The findings show the "need to establish training programs that are rigorous and competitive, but include varied training in lower-impact activities to decrease the cumulative amount of impact in order to reduce the risk of stress fracture," wrote Allison E. Field, of Brigham and Women's Hospital and Harvard Medical School, and colleagues.

The study appears online and in the August print issue of the journal Archives of Pediatrics & Adolescent Medicine.

More information

The American Academy of Orthopaedic Surgeons has more about stress fractures.