Rehydration and recovery after exercise

Recent data. - Restoration of water and electrolyte balance is an essential part of the recovery process after exercise that results in sweat loss. Ingestion of plain water results in a fall in plasma sodium concentration and osmolality, reducing the drive to drink and stimulating urine output. Addition of sodium and potassium to rehydration fluids will decrease urine output in the hours after rehydration. Because of urine losses, subjects are in net negative fluid balance throughout the recovery period, unless the volume ingested exceeds the loss. Urine output is inversely proportional to the sodium concentration of the ingested fluid. Ingestion of large volumes of fluid is not effective in maintaining positive fluid balance without electrolyte replacement. Ingestion of solid food together with plain water is effective in maintaining fluid balance if the electrolyte content is adequate. Addition of alcohol to ingested fluids has little effect in concentrations of 1 % or 2%, but there is a tendency for a diuretic effect that becomes significant at an alcohol concentration of about 4%. Ad libitum intake is strongly influenced by palatability. Conclusion. - Rehydration will only be achieved if a volume of fluid in excess of the sweat loss is ingested together with sufficient electrolytes. (C) 2004 Elsevier SAS. All rights reserved.