Cross-sectional evidence of suppressed bone mineral accrual among female adolescent runners

Abstract

We aimed to evaluate patterns of bone mineral accrual among a cross-sectional sample of female adolescent runners and girls participating in a nonendurance running sport. One-hundred and eighty-three interscholastic competitive female athletes (age 16.0 AE 0.1 years), 93 endurance runners and 90 nonrunners, completed a menstrual and sports history questionnaire, had their height and weight measured, and underwent a dual-energy X-ray absorptiometry scan for the measurements of body composition and bone mass. For the majority of analyses, the girls were separated into four groups according to their age (13 to 14 years, 15 years, 16 years, and 17 to 18 years). Runners' height, weight, body mass index (BMI), percent body fat, lean tissue mass, number of menstrual cycles in the past year, and months of participation in a non-lean-build/variable-impact-loading sport were significantly lower than mean values for nonrunners. Although bone mass rose at all sites in the nonrunners between the ages of 13 to 14 years and 17 to 18 years, no such increase was noted in the runners. Runners compared with nonrunners exhibited significantly lower body weight and height-adjusted total body and lumbar spine bone mineral content (BMC) values and lower bone mineral density (BMD) Z-score values among the older (16 years and/or 17 to 18 years) but not younger (13 to 14 years and/or 15 years) age groups. These findings suggest that the runners, in contrast to the nonrunners, exhibited a suppressed bone mineral accrual pattern, which supports the notion that female adolescent endurance runners may be at risk for inadequate bone mass gains and thus a low peak BMD. ß

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“…Long-distance runners are at a higher risk of sustaining stress injuries to bone as a result of their high training volume (and thus increased exposure of bone to repeated stress), potential biomechanical imbalances (such as pes planus, leg length discrepancy, or increased Q angle), 19,54 and risk of undernutrition. 5,6,20,38 Of the 34 athletes with bone stress injuries in this study, 22 (65%) were female ( Table 2), suggesting that women in the study were at higher risk. Multiple prior studies have reported similar findings.…”

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“…There appears to be a dose-response relationship between energy availability and markers of bone turnover in exercising females [ 45 ] and bone turnover markers are lower in athletes with amenorrhea [ 40 ]. Distance runners seem to be at especially high risk for inadequate bone mass accrual as a cross-sectional study of female adolescent runners showed no signifi cant difference in bone mineral content between runners ages 13-14 and 17-18, which was in contrast to non-runners who had normal increase in bone mineral content with age [ 46 ]. Additionally, as the number of risk factors for the Triad increases, there is a greater risk of low bone mineral density [ 47 ].…”