The effect of sodium and carbohydrate in a rehydration beverage when consumed as a meal on subsequent exercise performance

Abstract

The purpose of this investigation was to assess whether a food (chicken noodle soup) consumed during the initial stages of recovery from exercise in the heat improves subsequent temperature regulation and exercise performance by improving fluid retention and restoring plasma volume close to euhydrated levels. Ten subjects were studied during 2 h of rehydration after a 2.7% body mass loss. In a randomized crossover design, subjects rehydrated with chicken noodle soup (Soup: 161.0 mmol/l Na, 5.3 mmol/l K) or sugar-free Kool Aid® (14.4 mmol/l Na, 1.6 mmol/l K). Subjects ingested 175 ml at the start of rehydration and 20 min later; H2O was given every 20 min thereafter for a total volume equal to body mass loss during dehydration. At the end of the rehydration period, plasma volume and fluid balance were similar between treatments, although urine volume was greater in the Placebo trial (P = 0.06). Plasma osmolality (P < 0.02) and plasma sodium (P < 0.02) were significantly higher during rehydration in the Soup trial. After rehydration, subjects performed 30 min of steady state exercise (SSE) at 70% VO2peak followed by a time trial (TT) (30 min @ 70% VO2peak) with no further fluid intake. Neither beverage conferred cardiovascular or temperature regulation benefits during SSE. There was a trend for improved performance (P = 0.127) with soup ingestion (Soup 30.6 ± 0.9 min; Placebo 32.2 ± 1.5 min). Future research is needed to determine whether ad libitum rehydration during the rehydration period, SSE, and TT provides benefits in temperature regulation and exercise performance.