Goforth, H. W., & Koreerat, N. (2009). Hyperhydration in resting trained males: Effects of solutions with differing concentrations of sodium. ACSM 56th Annual Meeting, Seattle, Washington, Presentation Number 2103.

This study compared the retention of three hyperosmotic saline solutions and ability to increase total body water of resting athletes. Aerobically trained males (N = 9) were randomly assigned to group A, B, or C. Treatment order was; A-B-C; B-C-A, or C-A-B respectively. Trials were three hours conducted more than three days apart. Ss followed behavioral/dietary guidelines 72 hours before testing. Urine density verified euhydration status. The base solution for treatments made from a 50% diluted sports drink, contained; 100 mg Na, 90 mg K, and 7 g CHO. NaCl was added to make three saline solutions: S 30-30 mmol/L (0.91 g NaCl; the full strength sports drink): S 60-60 mmol/L (1.8 g NaCl), and S 90-90 mmol/L (3.6 g NaCl). Treatment volume (1.4 ± 0.14 L) was 3% of a S's estimated total body water. Urine output, urine density, plasma osmolality, hematocrit, and hemoglobin were measured hourly. Ss remained seated except to empty bladders.

Urine density decreased over time but did not differ between treatments. Hematocrit and hemoglobin values did not change significantly, indicating a constant red cell volume. Drinking 1.4 L of a 30 mmol/L Na solution (equal to a sports drink with the most Na) produced a net loss of body water. Drinking 1.4 L of the 60 and 90 mmol/L solutions allowed Ss to retain 25% and 35% of body water, and may be ergogenic for some athletes.

Implication. Sports drinks supplemented with extra salt cause a greater retention of body water than standard drinks. Extra salt in drinks in conditions conducive to dehydration would seem to be of value.

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