ARS | Publication request: Body Mass, Training, Menses, and Bone in Adolescent Runners: A 3-y Follow-Up

Submitted to: Medicine and Science in Sports and Exercise
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 2010
Publication Date: May 1, 2011
Citation: Barrack, M.T., Van Loan, M.D., Rauh, M.J., Nichols, J.F. 2011. Body Mass, Training, Menses, and Bone in Adolescent Runners: A 3-y Follow-Up. Medicine and Science in Sports and Exercise. Vol. 43, No. 6, pp. 959-966.

Interpretive Summary: Physical activity and participation in athletic events has increased dramatically since the passage of Title IX banning discrimination of athletics on the basis of sex. While participation in physical activity has many benefits it does have side-effects when participation is too physically demanding. Research has shown that high demand physical activity of adolescent female athletes can result in menstrual disruptions and lower bone mass accural during the important “formative” years. No research to date has examined longer term consequences of this lower bone accural during early adolescents. We investigated eating attitudes, training schedules, menstrual function and changes in bone density in a 3-year follow-up study of young women. We found that 87% of young women with low bone mass as an adolescent continued to have low bone mass at the 3-y follow-up. This low bone mass was explained in part, from 19-53%, by the amount of training, menstrual function, age, developmental stage, and change in body weight. This study suggests that delayed bone accural may result in lower bone mass as a young adult and thus emphasize the importance of gaining adequate bone mass during early adolescence.

Technical Abstract: Abstract: Endurance runners with low bone mass during adolescence may be at risk of developing a low peak bone mineral density (BMD) as a young adult. However, it is possible that they mature late and undergo delayed bone mass accumulation. PURPOSE: We evaluated 40 adolescent runners (age 15.9 ± 0.2y) at two time points, approximately 3 years apart, to assess bone mass status and identify variables associated with bone mass change. METHODS: Follow-up measures included the Eating Disorder Examination Questionnaire (EDE-Q), a menstrual status, training, and sports participation history questionnaire, 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 the -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 (BL) had low BMD at the follow-up. Girls with low compared to normal BL bone mass had lower follow-up adjusted total body (2220.4 ± 65.8g vs. 2793.1 ± 68.2g, P<0.001), total hip (27.0 ± 1g vs. 33.9 ± 1.0g, P< 0.05), and lumbar spine (47.8 ± 2.0g vs. 66.3 ± 2.2g, P< 0.001) BMC values. Variables related to girls' training volume, menstrual function, age, developmental stage, and change in body mass explained 19% to 53% of the variability in BMC change. CONCLUSION: Since the majority of adolescent runners with low BMD at BL also had low BMD after a 3-y follow-up, our observations suggest that a delayed accelerated accumulation phase may not occur under normal conditions, thus emphasizing the importance of gaining adequate bone mineral during the early adolescent years.