Comparison of Sports Drink Versus Oral Rehydration Solution During Exercise in the Heat

Michael W. Schleh, Charles L. Dumke

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

Introduction: This study compared 2 commercially available beverages, an oral rehydration solution (ORS; 60.9 mM Na+; 3.4% carbohydrate) and a sports drink (SDS; 18.4 mM Na+; 5.9% carbohydrate), on hydration and metabolism during submaximal exercise in the heat. Methods: Ten male subjects completed two 90-min exercise trials (39ºC, 30%) of walking at 50% VO2max followed by a 30-min rest period in the heat while wearing wildland firefighter personal protective clothing. After 45 min of exercise, fluid delivery by either ORS or SDS replaced 150% of sweat loss. Subjects continued the exercise for 45 additional minutes followed by a 30-min rest period. Blood samples were collected pre-exercise (0 min), post-exercise (90 min), and post-trial (120 min) to measure plasma volume (%) and blood glucose (mg·dL-1). Expired gases were collected twice for 3 min for substrate oxidation. Results: The sweat rate and percent dehydration did not differ between the groups (P=0.86 and P=0.79, respectively). Changes in plasma volume did not differ (P=0.55). Hemoglobin levels significantly increased in both groups post-trial (P=0.009). Blood glucose was significantly greater post-trial in SDS versus ORS (116±19 vs 103±13 mg·dL-1, respectively; P=0.01). Fat oxidation was lower post-exercise in SDS vs ORS (0.38±0.1 vs 0.47±0.2 g·min-1, respectively; P=0.049). Conclusions: These data indicate no difference in fluid retention between ORS or SDS when supplemented during exercise in the heat. This implies that fluid volume, and not drink contents, may be more important when ingested during exercise in a hot environment.

Original languageEnglish
Pages (from-to)185-193
Number of pages9
JournalWilderness and Environmental Medicine
Volume29
Issue number2
DOIs
StatePublished - Jun 2018

Funding

Acknowledgments: The authors thank the subjects for their time and energy in their volunteer effort. This study would not have been possible without Kansas Suenram, Keagan Shillington, Micah Drew, Brittany Hanser, Julia Guilliams, Thane Thompson, Lindsey Eagleman, and Manuel Dote Montero as research assistants in data collection. This study was supported by the US Forest Service (14-CR-11138200-009).

FundersFunder number
U.S. Forest Service-Retired14-CR-11138200-009

    Keywords

    • fluid retention
    • heat stress
    • hydration
    • rehydration
    • wildland firefighter

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