Sport Specialization and Low Bone Mineral Density in Female High School Distance Runners

Abstract

Context Sport specialization may contribute to sport injury and menstrual dysfunction in female high school distance runners. Despite the recent growth in sport specialization, including among high school–aged runners, the association of sport specialization with bone mineral density (BMD) remains poorly described. Objective To evaluate whether sport specialization was associated with BMD in female high school distance runners. Design Cross-sectional study. Setting Six high schools. Patients or Other Participants Sixty-four female runners (age = 15.6 ± 1.4 years) who competed in cross-country or track distance events and were not currently on birth control medication. Main Outcome Measure(s) Each runner completed a survey on menstrual history and sport participation. Height and weight were measured, and dual-energy x-ray absorptiometry was used to measure whole-body, spine, and hip BMD. Each runner was assigned a sport specialization status: low (participation in ≥1 nonrunning sport and distance-running sport(s) for ≤8 mo/y); moderate (participation in both distance-running sport(s) ≥9 mo/y and ≥1 nonrunning sports or limited to distance-running sport(s) for ≤8 mo/y); or high (participation only in distance-running sport(s) for ≥9 mo/y). Multivariable logistic regression was performed to determine the adjusted odds ratio and 95% confidence interval for sport specialization to BMD values, adjusting for body mass index and gynecological age. Results Overall, 21.9%, 37.5%, and 40.6% of participants were high, moderate, or low sport specializers, respectively. Low BMD (spine or whole-body BMD z score < −1.0 [standardized by age and sex normative values] was present in 23 runners [35.9%]). Compared with low sport specializers, high sport specializers were 5 times more likely (adjusted odds ratio = 5.42, 95% confidence interval = 1.3, 23.3; P = .02) to have low BMD. Conclusions A high level of sport specialization in high school female distance runners may be associated with a heightened risk for low BMD. Further investigation of this association is warranted due to the health concerns about low BMD in adolescent female runners.

Enhanced Bone Size, Microarchitecture, and Strength in Female Runners with a History of Playing Multidirectional Sports

“…The lower lumbar spine aBMD in RUN compared with reference data possibly reflects the systemic demands of distance running in terms of its impact on energy availability and circulating hormone levels. Twenty-one percent (3 of 14) of participants (19), who reported that high school distance athletes who highly specialized in running (i.e., participation in distance running only and for ≥9 months•yr −1 ) were five times more likely to have low aBMD compared with low sport specializers (≥1 nonrunning sport and distance-running sport/s for ≤8 months•yr −1 ). Lower whole-body bone mass and lumbar spine aBMD have prospectively been shown to be predictive of BSI in female athletes (32).…”

“…However, a focus on running activities when younger, at the expense of participating in other sports, may also play a role. Female high school distance runners who highly specialized in distance running (running >9 months·yr −1 with no participation in other sports) were found to have lower spine aBMD than those who did not specialize (19).…”

Bone health in Norwegian female elite runners: a cross-sectional, controlled study

“…Low BMD has earlier been observed in long-distance runners, despite competing in a weight-bearing sport. [10][11][12][13][14] Most studies have focused on elite adolescent runners 12 13 or adult runners below the elite level. 11 Barrack et al 12 observed low BMD (Z-score <−1) in 39.8% of female adolescent runners.…”

“…Low BMD has earlier been observed in long-distance runners, despite competing in a weight-bearing sport 10–14. Most studies have focused on elite adolescent runners12 13 or adult runners below the elite level 11. Barrack et al 12 observed low BMD (Z-score <−1) in 39.8% of female adolescent runners.…”

Relative Energy Deficiency in Sport (RED-S) in Adolescents – A Practical Review

“…Young wrestling/judo participants and sprinters have been identified as having higher BMD than endurance athletes and swimmers, and those who are inactive [56][57][58]. A low BMD has been associated with adolescents who have specialised early into endurance running [59], and risk factors for low BMD in male adolescent runners include body weight < 85 % expected, weekly mileage > 30 miles, history of stress fracture and less than one serving of calcium per day [60]. Horse racing is a weight restricted sport and 29 % of entry level male flat jockeys (mean age 18.5 years) were identified as Review Thieme having Z scores < 2 [61], compared to 13 % of male jump jockeys where the weight restriction is less.…”