Co-consumption of sodium and water has been shown to be superior in promoting hyperhydration compared to consumption of an equal amount of water alone. Most sodium-aided hyperhydration studies have provided subjects with a bolus of fluid followed by a urine collection period. However the effect of providing equal amounts of fluid in a single vs. multiple doses over time on fluid retention has not been systematically studied. PURPOSE: To compare the effects of different dosing strategies on urine excretion levels following the consumption of consistent amounts of sodium and water. METHODS: Urine excretion was measured during five separate 2-hr hyperhydration protocols in 13 well hydrated male subjects (23 ± 3 yr, 176.1 ± 10.1 cm, 82.2 ± 19.4 kg) who were free from known renal, digestive, and cardiovascular disease. Each protocol began with a complete bladder void and assessment of urine specific gravity (USG). Subjects then consumed 20 mL H2O ∙ kg bm-1 and 110 mg NaCl ∙ kg bm-1 in five different dosing strategies: the entire dose was consumed at the beginning of the period (1X), ½ of the dose was consumed at the beginning and ½ consumed after 60 min (2X), and 1/3 of the dose was consumed at the beginning and 1/3 was consumed after 45 and 90 min (3X), ¼ of the dose was consumed at the beginning and after 30, 60, and 90 min (4X), and 1/7 of the dose was consumed at the beginning and after 15, 30, 45, 60, 75, 90 min (7X). Protocols were administered in a randomized, crossover fashion. Total urine excretions (TUE) during the 2 hr collection periods were expressed as a percent of the H2O consumed. USG and TUE were compared using repeated-measures ANOVA and Sidak post hoc analyses. RESULTS: USGs were 1.006 ± 0.004 (1X), 1.007 ± 0.003 (2X), 1.009 ± 0.005 (3X). 1.007 ± 0.004 (4X), and 1.007 ± 0.005 (7X) (P = 0.37 – 1.00) indicating that subjects were well and similarly hydrated for each trial. TUE expressed as a percentage of H2O consumed were 75 ± 18% (1X), 69 ± 11% (2X), 52% ± 15% (3X), 59 ± 15% (4X), and 60 ± 16% (7X). Significant differences in TUE were seen between 1X and 3X (P = 0.03) and 2X and 3X (P = 0.006). No significant difference in TUE was detected between any of the other protocols (P = 0.16 – 1.00). CONCLUSION: The data suggest that hyperhydration is better achieved when water and sodium are consumed in three equal doses over 90 min when compared to consuming an equal amount of a sodium and water dose in a single bolus or in two equal doses over a 60 min period. Consuming water in four or seven equal doses over 90 min did not result in better fluid retention than consuming an equal amount of water in a single bolus or in two equal doses over a 60 min period.
Greene, Shelby L.; Roslanova, Elizaveta; and Morris, David
"Effects of Dose Timing on Fluid Excretion During Sodium-Aided Hyperhydration Protocols,"
International Journal of Exercise Science: Conference Proceedings: Vol. 2
, Article 63.
Available at: http://digitalcommons.wku.edu/ijesab/vol2/iss9/63