Effect of preexercise electrolyte ingestion on fluid balance in men and women.

Purpose: This article aimed to study the effect of preexercise ingestion of an electrolyte-containing beverage and meal on fluid balance during exercise in men and women. Methods: Twenty healthy, college-aged people (10 males, 10 females; mean +/- SD = 51.2 +/- 9.8 mL[middle dot]kg-1[middle dot]min-1) exercised at 58 +/- 4% V[spacing dot above]O2peak for 90 min, 45 min after ingesting 355 mL of chicken noodle soup (SOUP; 167 mmol[middle dot]L-1 Na+), carbohydrate-electrolyte beverage (CE; 16 mmol[middle dot]L-1 Na+), or water (WATER). After 90 min of exercise, participants completed a physical performance task (PPT) consisting of the calculated work that would be completed in 30 min at 60% V[spacing dot above]O2peak (n = 19). Water was allowed ad libitum throughout all trials. -Results: Fluid balance was improved in SOUP compared with WATER (-251 +/- 418 vs -657 +/- 593 g, respectively; P = 0.002) because of greater water intake and retention throughout the trial. Water intake was also greater in CE compared with WATER mostly because of an increase during the PPT. Plasma osmolality increased after ingestion of SOUP and remained elevated throughout exercise compared with both CE and WATER. Men and women had similar fluid balance results, with women having lower relative water intake and evaporative water losses compared with men. Physical performance was similar in all trials. Conclusions: SOUP ingested before exercise improves fluid balance because of increased ad libitum water intake and reduced proportional urinary water loss. The increase in water intake and, subsequently, the improved fluid balance may be because of a greater plasma osmolality before and throughout exercise.