Hydration, Ad Libitum Consumption, and Performance are Similar Between a Milk Permeate Solution, a Traditional Sports Drink, and Water Following Overnight Fluid Restriction in Recreationally Active Adults
Authors: Berry Craig W. , Wolf S. T. , Kenney W. L. 
Published: May 2022

Body water volume is tightly regulated such that the daily variation in total body water content is less than 1%. Imbalances in fluid volume can occur when fluid is not freely available, and can lead to decrements in physical performance when water losses exceed 2% body mass. Thus, it is essential to assess strategies that promote fluid replacement and retention during and following exercise. Beverages containing milk permeate have been suggested to be an efficacious alternative to traditional sports drinks for restoring hydration and maintaining performance. However, no prior studies have examined how consumption of such a beverage following overnight fluid restriction affects exercise performance in recreationally active individuals, or how ad libitum (AD) consumption following exercise affects indices of hydration, compared to other beverages.PURPOSEWe aimed to (1) determine how overnight fluid restriction and next‐day prescribed rehydration with either water (WAT), GatoradeÔ (GAT), or a milk permeate solution – GoodSportÒ (GS) – affects cycling time trial (TT) performance, and (2) compare the impact of ad libitum consumption of these three beverages on restoration of fluid balance and biomarkers of hydration status post‐TT.HYPOTHESESWe hypothesized that (1) time‐trial performance would be similarly improved following consumption of GAT and GS compared to WAT, and 2) ad libitum fluid consumption post‐time‐trial would be greater for GAT and GS compared to WAT.METHODSFour (3M/1F) recreationally active (>150min/wk) young adults (25±1yr) completed 3 experimental visits consisting of a 15‐hr overnight fluid restriction prior to arrival at the laboratory for exercise trials. Subjects cycled at a moderate intensity (50% VO2max, 60 RPM) for one hour in a warm environment (30°C, 20% relative humidity) while consuming 2 mL/kg of randomly assigned fluid every 10 minutes, followed by a 5‐km TT. Following the TT, subjects cycled for one hour at 25% VO2max and were instructed to drink the randomly assigned fluid ad libitum.RESULTSTT performance, measured as both time and watts per kilogram (W/kg), was not different among trials (WAT: 562±36 sec, 2.2±0.4 W/kg; GAT: 570±58 sec, 2.3 ± 0.5 W/kg; GS 575±29 sec, 2.1 ± 0.6 W/kg; all p>0.21). AD consumption was not different among trials (WAT: 1148±638 mL; GAT: 1200±355 mL; GS: 1271±486 mL). There were no differences in percent change in plasma volume (%ΔPV) at any time point among beverage conditions (all p>0.28).CONCLUSIONTT performance, measured as both time and W/kg, was not improved following prescribed consumption of a milk permeate solution (GS) or a traditional sports drink (GAT) compared to WAT. AD fluid consumption was not different among beverage conditions during the one‐hour recovery cycling period after the TT. Changes in plasma volume, an important indicator of hydration, was not different among drink conditions at any time‐point, indicating subjects were similarly hydrated among beverage conditions.