Abstract
The assessment of hydration status via urinary indices is common practice among many athletes. However, numerous factors are known to violate the use of urinary indices, including rapid rehydration and caffeine consumption. Although an increase in dietary sodium intake is encouraged to achieve fluid balance restoration when in a hypohydrated state, the influence of an acute elevation in dietary sodium intake on urinary indices of hydration status has not been addressed. The purpose of this investigation was to determine if dietary sodium intake violates the use of urinary indices of hydration status. It was hypothesised that an acute elevation in dietary sodium intake influences fluid regulatory hormone concentrations and thus urinary constituents, independent of total body water, masking hydration status and invalidating the use of urinary indices. Volunteers (n=12) were randomly assigned to either an elevated (200 mmol) or normal (80-100 mmol) sodium treatment group for 24 h in this randomised, cross-over investigation. A washout period of 48 h was enforced prior to each intervention. Food and fluid intake during the washout and intervention periods was provided. Urinary and haematological indices were monitored throughout the investigation, along with total body water, electrolyte and fluid regulatory hormone concentrations. Data were compared using general linear modeling with dietary sodium intake and trial number as fixed effects, subject as a random effect and total body water as a covariate. Results and conclusions available by June.