Beverage Composition Influences Ad Libitum Consumption, Hydration Status And Affect During Exercise In The Heat

Abstract

Maintaining a sufficient level of hydration can have a substantial effect on performance outcomes, especially in endurance exercise. How an exerciser feels (pleasure vs. displeasure) could in theory, depend on their ability to maintain fluid balance, ultimately affecting their performance. PURPOSE: To determine the effect of ad libitum consumption of either a carbohydrate-electrolyte beverage (CES), water (WAT), or a electrolyte-free, non-caloric, flavor-matched placebo drink (PLA) on hydration status and affective responses. METHODS: Seventeen trained men (mean±SD; 25.4±4.0 y, VO2peak = 53.3±6.8mL kg-1 min-1) completed three intervention trials in a randomized, double-blind, counter-balanced, cross-over design. Trials involved two hours of steady state (SS) cycle ergometry at 68.4±9.3% VO2peak in the heat (WBGT=24.4±1.7°C) with ad libitum WAT, PLA, or CES. Indices of affective responses and fluid balance were recorded prior to and every 30 min during SS cycling exercise. RESULTS: Physiologically, plasma glucose was significantly greater with CES than WAT and PLA for all time points during SS (p<0.05). A significant difference was found in plasma sodium levels at 120 min (p<0.05). Plasma osmolality was significantly greater with CES compared to WAT at 90 min (p<0.05), and significantly greater than WAT and PLA at 120 min (p<0.05). Greater fluid intake was observed at all time points with CES compared to water (p<0.05). CES elicited significantly greater mean affective response than PLA and WAT only at 120 min (p<0.05). CONCLUSION: Greater affect during CES appears to be supported by a greater fluid intake and plasma osmolality, possibly due to the higher plasma glucose and sodium levels compared to other treatments. Thus, the improved fluid balance in the CES condition may have contributed to the improved feelings of affect (more pleasure) at the end of 2 hrs of SS cycling exercise, which was independent of flavor due to the flavor-matched PLA. Collectively, affective responses appear sensitive to changes in indices of hydration status during prolonged endurance exercise in hot environmental conditions. As such, affect may reflect a signal to induce drinking behaviors that maintain fluid balance and protect bodily homeostasis. Funded by The Coca-Cola Company NCT01893853