Postexercise rehydration in man: The effects of osmolality and carbohydrate content of ingested drinks

• Published in: Nutrition (Burbank, Los Angeles County, Calif.) Vol. 25; no. 9; pp. 905 - 913
• Main Authors: Evans, Gethin H., Shirreffs, Susan M., Maughan, Ronald J.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.09.2009; [New York]: Elsevier Science Inc; Elsevier; Elsevier Limited
• Subjects: Adult; Beverages; Bicycling; Bicycling - physiology; Biological and medical sciences; blood; Blood Volume; Blood Volume - drug effects; carbohydrate content; Dehydration; dehydration (animal physiology); Dehydration - physiopathology; Dehydration - therapy; Dietary Carbohydrates; Dietary Carbohydrates - pharmacology; Dietary Carbohydrates - therapeutic use; Drinking; drug effects; exercise; Exercise - physiology; Feeding. Feeding behavior; Fluid balance; Fluid retention; fluid therapy; Fluid Therapy - methods; Fluids; Fundamental and applied biological sciences. Psychology; Gastroenterology and Hepatology; Glucose; Glucose - pharmacology; Glucose - therapeutic use; Humans; liquids; Male; men; methods; osmolality; Osmolar Concentration; pharmacology; physiology; physiopathology; Plasma; Sodium; Sodium - pharmacology; Sodium - therapeutic use; Solution osmolality; Studies; therapeutic use; therapy; Urine; Urine production; Variance analysis; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Fluid balance; Fluid retention; Solution osmolality; Urine production; Dehydration; Human; Urine; Hydroelectrolytic balance disorder; Retention; Vertebrata; Mammalia; Rehydration; Carbohydrate; Balance
• ISSN: 0899-9007; 1873-1244; 1873-1244
• DOI: 10.1016/j.nut.2008.12.014

This study investigated the effect of the osmolality and carbohydrate content of drinks on their rehydration effectiveness after exercise-induced dehydration. Six healthy male volunteers were dehydrated by 1.9 ± 0.1% of body mass by intermittent cycle ergometer exercise in the heat before ingesting one of three solutions with different carbohydrate contents and osmolalities over a period of 1 h. Thirty minutes after the cessation of exercise, subjects drank a volume that amounted to 150% (130–150, median [range]) of their body mass loss. Drinks contained 25 mmol/L Na + and 0%, 2%, or 10% glucose with osmolalities of (mean ± SD) 79 ± 4, 193 ± 5, and 667 ± 12 mosm/kg, respectively. Blood and urine samples were collected before exercise, after exercise, and 0, 1, 2, 3, 4, and 6 h after the end of the rehydration period. Significantly more of the ingested fluid was retained in the 10% trial (46 ± 9%) than in the 0% trial (27 ± 13%), with 40 ± 14% retained in the 2% trial. Subjects remained euhydrated for 1 h longer in the 10% glucose trial than in the 2% glucose trial. In the 2% glucose trial, plasma volume was elevated immediately after and 1 h after rehydration. This study suggests that, following the rehydration protocol used, hypertonic glucose-sodium drinks may be more effective at restoring and maintaining hydration status after sweat loss than more dilute solutions when the sodium concentration is comparable.