Cory L. Butts, Aaron R. Caldwell, Kathleen M. Heath, J.D. Adams, Matthew S. Ganio, FACSM, Lisa T. Jansen, Hyun-Gyu Suh, Leslie W. Vandermark, Brendon P. McDermott; University of Arkansas, Fayetteville, AR

American football athletes often report to practices and games in a hypohydrated state, potentially placing them at risk for performance and thermoregulatory impairments. PURPOSE: Evaluate the hydration status of high school American football players at various intervals during preseason practices and assess the clinical utility of spot-check urine sampling for identifying sub-optimal hydration. METHODS: Thirty-one male, high school American football players (age 16 ± 1y, ht 179.0 ± 6.6cm, mass 88.4 ± 19.9kg, body fat 19.9 ± 9.4%) participated in this observational study. Body mass (BM), blood, and urine samples were obtained 2-3 days prior to the start of (Baseline) and at Days 4 (D4), 7 (D7), and 10 (D10) of pre-season practices. On D4 and D7, samples were collected prior to the start of practice while D10 samples were obtained post-practice. Serum osmolality (Sosm) was analyzed via freezing point depression. Urine specific gravity (USG) and urine color (Ucolor) were also measured. Receiver operating characteristic-area under the curve (ROC-AUC) analysis was used to assess sub-optimal hydration identification via urine, with Sosm as the standard. Sub-optimal hydration status for each marker was defined as BM loss >1% from baseline, Sosm >290 mOsm/kg, USG >1.020, and Ucolor >4. RESULTS: BM did not change significantly over time (P = 0.26). BM loss of >1% was present in 37% and 42% of players prior to practice on D4 and D7, respectively. Sosm was 292 ± 4, 293 ± 4, 294 ± 6, and 295 ± 4 mOsm/kg for Baseline and D4, D7, and D10, respectively, with only D10 significantly elevated from Baseline (P = 0.05). Further, 67-73% of players reported to practice, and 80% finished practice, with Sosm >290 mOsm/kg. USG at Baseline and D4, D7, and D10 were 1.023 ± 0.007, 1.018 ± 0.009, 1.019 ± 0.009, and 1.027 ± 0.005, respectively (P <0.001). Ucolor from Baseline through D10 were 4 ± 1, 3 ± 1, 3 ± 1, and 4 ± 1, respectively (P = 0.003). USG identified sub-optimal hydration with a ROC-AUC of 0.72, a sensitivity of 0.71 and a specificity of 0.50. The ROC-AUC using Ucolor to identify sub-optimal hydration was 0.60 with a sensitivity of 0.18 and a specificity of 0.97. CONCLUSIONS: In congruence with prior literature, at least two-thirds of players reported for or completed practice sub-optimally hydrated, as identified via Sosm. Furthermore, the spot-urine samples did not provide accurate diagnostic value for identifying inadequate hydration. Thus, clinicians should encourage fluid consumption prior to and during practice throughout pre-season activity, however caution should be used if spot-urine samples are collected to identify sub-optimal hydration.

Funded by AMSSM-ACSM Clinical Research Grant

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