Body mass, training, menses, and bone in adolescent runners: a 3-yr follow-up.
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.


OBJECTIVE
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.
Barrack
Michelle T
MT
Graduate Group in Nutritional Biology, University of California Davis, Davis, CA, USA. michellebarrack@gmail.com
Van Loan
Marta D
MD
Rauh
Mitchell J
MJ
Nichols
Jeanne F
JF
D015502:Absorptiometry, Photon; D000293:Adolescent; D000367:Age Factors; D056352:Athletes; D050218:Body Fat Distribution; D001827:Body Height / Q000502:physiology; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology; D015519:Bone Density / Q000502:physiology*; D003278:Contraceptives, Oral, Hormonal / Q000627:therapeutic use; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016014:Linear Models; D008597:Menstrual Cycle / Q000502:physiology*; D008599:Menstruation Disturbances / Q000188:drug therapy / Q000453:epidemiology; D012420:Running / Q000502:physiology*
D003278:Contraceptives, Oral, Hormonal