Sport Specialization Is Not Associated With Relative Energy Deficiency Risk Factors In High School Runners

Sport specialization has been associated with increased risk of overuse injury in many sports; however, the prevalence of specialization in youth distance runners is not well understood. Overuse injury risk is also influenced by risk factors for relative energy deficiency in sport (RED-S). As runners are especially at risk for overuse injuries, including bone stress injuries (BSI), determining the association between specialization and RED-S risk factors is important for developing future injury risk reduction strategies. Purpose: To determine the prevalence of and associations between sport specialization, prior BSI, and risk factors for RED-S in high school cross country runners. Methods: Cross country runners at 24 high schools completed a pre-season survey regarding current sport specialization, number of prior BSI, and RED-S risk factors (low bone mineral density [BMD] diagnosis, prior eating disorder, weight concerns). Specialization was scored on a 0-3 point scale (0-1 = low, 2 = moderate, 3 = high). Prevalence of variables of interest were calculated as percent of the total sample. Logistic regressions or Fisher’s exact tests were used as appropriate to assess associations between specialization and RED-S risk factors, controlling for sex and grade in school. Results: Responses from 315 (171 female) runners were analyzed, with 23% classified as highly specialized, compared to 33% and 44% classified as moderate and low specialized, respectively. Ten percent of runners reported at least 1 prior BSI (range: 0-3). Prevalence of risk factors for RED-S was generally low; 1.6% reported a prior eating disorder and 1.0% had received a low BMD diagnosis, while 22.5% worried about their weight. Highly specialized runners reported more prior BSI than low specialized (p = 0.04). Level of specialization was not associated with weight concerns (p = 0.69), prior eating disorder (p = 0.34), or prior low BMD diagnosis (p = 0.34). Conclusions: High school runners demonstrated levels of sport specialization consistent with trends in other sports, and high specialization was associated with increased number of prior BSI. As RED-S risk factors did not vary by level of specialization, monitoring of both sport specialization and factors related to RED-S may be warranted when assessing potential risk for overuse injuries.