Relationship between changes in upon-waking urinary indices of hydration status and body mass in adolescent Singaporean athletes
Journal Title (Medline/Pubmed accepted abbreviation): Int. J. Sport Nutr. Exerc. Metab.
Year: 2010
Volume: 20
Page numbers: 330-335
doi (if applicable):

Summary of Background and Research Design

Hypothesis/purpose of study: Staying well hydrated is imperative for optimum sports performance. Is the color (Ucol) and specific gravity (Usg) of urine able to be determined by athletes in order to personally assess hydration status? Is a change in body weight reflective of hydration status?

Subjects: 36 male and 30 female Singaporean adolescent athletes (average age = 15 y, average body weight = 55 and 53 kg for males and females, respectively). The athletes were enrolled in a Singaporean sports camp and participated in sports such as soccer, netball, swimming, and track and field.

Treatments and protocol:Urine and body weight measurements were acquired on 5 consecutive mornings after a >=8 hr overnight fast. Participants assessed Ucol as well as the investigators using a visual 9-point color scale. Usg was measured using a refractometer.

Summary of research findings:
  • For every 1% change in body mass, Usg changed ≈0.003 units and Ucol. changed ≈1 unit (on a 9-point scale).
  • There was a strong correlation between Usg and the Ucol values obtained by investigators (R = 0.82, P < 0.001).
  • The correlation between Usg and the Ucol values obtained by the athletes was also statistically significant (R = 0.60, P < 0.001), but the magnitude of the correlation coefficient was lower compared with when trained professionals rated Ucol.

Interpretation of findings/Key practice applications:

Athletes may be able to use day-to-day changes in body mass as a surrogate marker for Usg to assess hydration status. Determining Ucol was associated with more error among the athletes themselves versus the investigators. As such, appropriate Ucol charts and training of athletes are required to provide more reliable ratings of Ucol.
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