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Body Mass, Training, Menses, and Bone in Adolescent Runners: A 3-yr Follow-up

BARRACK, MICHELLE T.1; VAN LOAN, MARTA D.2; RAUH, MITCHELL J.3,4; NICHOLS, JEANNE F.4

Medicine & Science in Sports & Exercise: June 2011 - Volume 43 - Issue 6 - p 959-966
doi: 10.1249/MSS.0b013e318201d7bb
Clinical Sciences

ABSTRACT Endurance runners with low bone mass during adolescence may risk attaining a low peak bone mineral density (BMD) in adulthood. Alternatively, they may mature late and undergo delayed bone mineral accumulation.

Purpose: The purpose of this study was to evaluate 40 adolescent runners (aged 15.9 ± 0.2 yr) at two time points, approximately 3 yr apart, to assess bone mass status and identify variables associated with bone mass change.

Methods: Follow-up measures included a questionnaire to assess menstrual status, training, and sports participation history, height and weight, and a dual-energy x-ray absorptiometry scan to assess total body, total hip, and lumbar spine BMD, bone mineral content (BMC), BMD z-score, and body composition. We used −1 and −2 BMD z-score cutoffs to categorize runners with low bone mass.

Results: Eighty-seven percent of girls with low BMD at baseline had low BMD at the follow-up. Girls with low compared with normal baseline BMD had lower follow-up adjusted total body (2220.4 ± 65.8 vs 2793.1 ± 68.2 g, P < 0.001), total hip (27.0 ± 1 vs 33.9 ± 1.0 g, P < 0.05), and lumbar spine (47.8 ± 2.0 vs 66.3 ± 2.2 g, P < 0.001) BMC values. Variables related to 3-yr training volume, menstrual function, age, developmental stage, and change in body mass explained 29%-54% of the variability in BMC change.

Conclusions: The majority of adolescent runners with low BMD at baseline had low BMD after a 3-yr follow-up. Our observations suggest that "catch-up" accrual may be difficult and, thus, emphasize the importance of gaining adequate bone mineral during the early adolescent years.

1Graduate Group in Nutritional Biology, University of California Davis, Davis, CA; 2US Department of Agriculture, ARS, Western Human Nutrition Research Center, University of California Davis, Davis, CA; 3Graduate Program in Orthopaedic and Sports Physical Therapy, Rocky Mountain University of Health Professions, Provo, UT; and 4School of Exercise and Nutritional Sciences, San Diego State University, San Diego, CA

Address for correspondence: Michelle T. Barrack, Ph.D.; E-mail: michellebarrack@gmail.com.

Submitted for publication October 2009.

Accepted for publication October 2010.

©2011The American College of Sports Medicine