PREDICTORS OF STRESS FRACTURE IN ACTIVE ADOLESCENT FEMALES

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Athletic participation has become increasingly common among adolescent females since the enactment of Title IX of the Educational Amendments Act in 1972, which required women's intercollegiate athletic offerings to be proportional to their representationin the student body. This has been a welcome trend to adolescent health care providers, as there are notable health benefits derived from an active lifestyle. A particular benefit for young women is the potential for improved skeletal health. Adolescence is the critical period in a yound woman's life for bone mass acquisition, with over half of the adult bone calcium laid down during the teenage years and a woman's peak bone density likely reached between the ages of 10 and 30 years. Weight-bearing exercise is a major stimulus for skeletal remodeling, increased bone mineralization, and thereby, increased bone density. maximizing bone mineral density (BMD) by participation in athletics during adolescence could result in the prevention of osteoporosis later in these young women's lives. Osteoporosis is currently a mojor cause of morbidity and mortality for over 20 million American women in their later years. Less is known about factors that contribute to stress fractures in adolescent girls. We hpothesize that many of the risk factors are the same as in adult women and have developed a pathogenetic model to describe and explain the relationships among them. We hypothesize that only low BMD and exercise directly influence the risk of stress fracture. We further hypothesize that amenorrhea increases the risk of stress fracture by negaively impacting on BMD. As adolescent health care providers, we are vexed by the lack of evidence upon which to answer the question, "How much exercise is safe?" We are particularly concerned about the safety of athletic participation by young women with amenorrhea. Our current standard of care calls for assessment of bone density by dual energy x-ray absorptiometry (DXA) in