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Objectives Inflammatory cytokine and immune cell production is modulated by iron status including storage measured by ferritin levels. Cross-country athletes have an elevated risk of iron depletion and stress fractures; the effects of a competitive season on inflammation, iron stores, and bone biomarkers have yet to be elucidated. The purpose of this study is to determine the influence of one season of NCAA Division I (D-I) cross-country competition has on TNF-α, serum ferritin (sFer), complete blood count (CBC), and various bone biomarkers to identify potential relationships. Methods Twelve D-I cross-country athletes, ages 19 to 25 years old, were followed for one year. Blood was collected at the beginning of each season and analyzed for CBC and sFer levels through enzymatic spectrophotometry. TNF-α, OPG, OPN, DKK1, SOST, PTH, FGF23, Insulin, and Leptin were measured through Luminex® MAGPIX® multiplex assays. Paired-samples t-test compared the 2017 preseason and 2018 preseason baselines, while Pearson correlations included both seasons. Statistical analyses were performed using IBM® SPSS Statistics 25 software. Results TNF-α levels increased significantly from 2017 to 2018 (9.5 ± 4.6 vs. 12.2 ± 4.9 pg/mL, P = 0.005) as well as DKK1 (544.4 ± 223.6 vs. 1167.0 ± 212.1 pg/mL, P < 0.001), while % Monocytes decreased significantly from 2017 to 2018 (10.7 ± 2.6 vs. 8.6 ± 1.9%, P = 0.003). sFer showed to have a moderate positive-correlation with TNF-α and OPG (r = 0.619, P = 0.002; r = 0.640, P = 0.001) throughout both preseason intervals. Conclusions Given TNF-α has shown to induce DKK1, both bone mineral density and bone biomarkers of the cross-country athlete needs to be continually assessed throughout multiple stages of their competitive season to insure proper bone health. Further investigation is needed into the potential causes for the increases of TNF-α and DKK1 observed in cross-country athletes. Funding Sources Weber State University's Office of Undergraduate Research Grant. Supporting Tables, Images and/or Graphs

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