Article Title



B Lints


Blaine Lints. University of South Carolina, Columbia, SC.

Background: Urine specific gravity (USG) is a commonly applied biomarker for rapid determination of hydration status. While USG benefits largely from convenience, it may not be as reflective of true hydration status when compared to serum osmolality (Sosm), the gold standard of hydration detection. Subsequently, decisions made regarding a team sport athlete’s readiness to play based on USG may warrant a certain degree of caution. Therefore, the purpose of this study was to assess the concordance between hydration status measured by USG and Sosm in male and female Division I soccer players. Methods: Sixty-four National Collegiate Athletic Association Division I soccer players (n = 31 women, n = 33 men; Mweight ± SE= 70.06 ± 0.90 kg; M%BF = 15.05 ± 0.94 %; MVO2max= 51.97 ± 0.76 mL/kg/min) participated in testing Blood draws and urine collection occurred in the morning and in a fasted state at six time points for the women and three time points for the men throughout the season. Data from all timepoints were compiled to determine mean ± SE for Sosm and USG. Pearson-product moment correlations were used to assess relationships between USG and Sosm. An alpha level of 0.05 was used to determine statistical significance. Results: Mean Sosm ± SE was 286.57 ± 0.39 mOsm/kg, while mean USG was 1.02 ± 0.00 for the women throughout the season. For the men, mean Sosm was 289.38 ± 0.61 mOsm/kg, while mean USG was 1.02 ± 0.00. In both women (r = -0.06, p = 0.42) and men (r = 0.02, p = 0.86), no statistically significant correlations were observed between USG and Sosm. Conclusions: These findings suggest a lack of agreement between USG and Sosm when assessed over the course of a collegiate soccer season. While USG is capable of quickly providing a field-based estimate of hydration status, coaches and athletes should be mindful of potential differences when compared to Sosm. In light of the fact that athletes routinely deal with significant variations in hydration status, the lack of correlation between USG and Sosm suggest an athlete may be mistakenly categorized as hydrated or dehydrated prior to sport practice or competition.

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