A Combination Of High Sodium And Potassium Leads To Better Rehydration During A 4-h Period

Since dehydration is very common during training and competition in the heat, rehydration is an essential part of recovery after training and competition. PURPOSE: The study aimed to observe the effectiveness of rehydration with different commercially available drinks and plain water. METHODS: On four separate occasions, ten young, healthy adults (2 females; age: 23 ± 2 y, weight: 73.3 ± 11.7 kg, height: 1.75 ± 0.08 m) completed a two-hour exercise-induced dehydration protocol in the heat (29.9 ± 1.5 °C), followed by a four-hour rehydration period. Trials were identical, with the only difference being the drink ingested for rehydration. The four drinks were: a) high sodium (HNa; Na: 457 mg/L), low potassium (K: 135 mg/L) with 6% carbohydrates (CHO); b) high K (HK; K: 1493 mg/L), low Na (85 mg/L) with 6% CHO, c) high Na, high K (HNaHK; Na: 480 mg/L, K: 1120 mg/L) with 4.4% CHO, and d) Water (W), that served as a control. Dehydration was induced by exercise at 70% of the estimated max heart rate and consisted of intermittent cycling and walking exercise for two hours or until reached -2% of body weight dehydration. The fluids equal to 150% of body weight loss were administered in four equal doses every 15 min during the first hour of the four-hour rehydration. RESULTS: Exercise-induced dehydration (~2% body weight) did not differ between the trials (P > 0.05). Rehydration with the HNaHK drink led to greater net fluid balance at the 4th hour of rehydration (-0.4 ± 0.2 kg; P < 0.05), compared to HNa: -0.7 ± 0.2 kg, HK: -1.0 ± 0.5 kg, and W: -0.9 ± 0.4 kg. Cumulative urinary output during the four hours of rehydration for the HNaHK trial was lower (1260 ± 190 mL) than the W: 1591 ± 517 mL (P < 0.05), and HK: 1827 ± 493 mL (P < 0.05), but not HNa: 1501 ± 219 mL (P = 0.07). At the end of the rehydration period, plasma osmolality remained higher during the HNaHK trial (289 ± 4 mmol/kg, P < 0.05) compared to HNa: 285 ± 4, HK: 283 ± 4, and W: 283 ± 4 mmol/kg. At the same time point, free water clearance was the lowest for the HNaHK: -2.9 ± 0.8 mL/min (P < 0.05) compared to the others (HNa: 1.2 ± 1.4, HK: 2.0 ± 1.3, W: 3.0 ± 3.0 mL/min). CONCLUSION: The data indicated that rehydration after exercise-induced dehydration with a drink containing high sodium and potassium was better when compared to a high sodium drink, high potassium drink, and plain water. Grant Funding Info: Funding provided by USDA Supported by: USDA