Divergent Findings Between Bone Mineral Density And Stress Fracture Incidence In Track And Field Athletes

Engagement in bone-loading physical activity is associated with improved bone mineral density (BMD) and reduced fracture risk. However, athletes competing in cross-country and track and field (XC + T&F) who consistently engage in anabolic skeletal exercises have a high bone injury incidence. PURPOSE: To compare Dual-energy X-ray Absorptiometry (DXA) derived bone measures and key factors that modulate skeletal health between XC + T&F and Controls and within XC + T&F based on stress fracture (SFx) history. METHODS: Forty-seven Division I XC + T&F and thirty physically active non-athlete Controls completed DXA scans, training, injury, sleep, and dietary logs. Independent t-tests and chi-square tests were performed between XC + T&F and Controls and within XC + T&F based on SFx history (SFx n = 18; None n = 29), α < 0.05. RESULTS: Despite XC + T&F and Controls being equivalent for age, height, body mass, body mass index, and sleep and dietary quality (all p ≥ 0.089), XC + T&F reported significantly greater SFx incidence (p = 0.023). Further, XC + T&F had higher BMD Z-Scores and percent lean body mass (LM%) (both p < 0.001). Within XC + T&F, SFx groups were equivalent for all anthropometrics, total body BMD Z-Score, LM%, weekly mileage, resistance training frequency, and sleep quality (all p ≥ 0.286). XC + T&F athletes with history of SFx had better Healthy Eating Index scores (p = 0.007); despite consuming significantly fewer calories per day (p = 0.04). Lastly, there was a significant association between SFx incidence and self-reported dietary restriction (χ2 (1, n = 47) =6.47, p = 0.011). CONCLUSION: Dietary restriction was associated with SFx incidence, independent of body composition or bone health metrics. These data suggest that many standard tools used to identify SFx risk in this cohort may lack sensitivity and more comprehensive screening tools are needed. This further supports the recent expansion of the relative energy deficiency in sport initiative.