Guidelines for Glycerol Use in Hyperhydration and Rehydration Associated with Exercise
- 1 February 2010
- journal article
- review article
- Published by Springer Science and Business Media LLC in Sports Medicine
- Vol. 40 (2), 113-129
- https://doi.org/10.2165/11530760-000000000-00000
Abstract
Dehydration in athletes alters cardiovascular and thermoregulatory function and may inhibit endurance exercise capacity if fluid loss exceeds 2% of bodyweight (BW). If this level of dehydration cannot be prevented when starting from a state of euhydration, then athletes may create a state of hyperhydration by consuming extra fluid prior to exercise. From this hyperhydrated situation, individuals have a greater capacity to tolerate fluid loss before becoming dehydrated. Furthermore, excess pre-exercise fluid intake enhances thermoregulatory ability, as well as increasing plasma volume to maintain cardiac output. However, hyperhydrating before exercise is difficult, because a large fluid intake is typically accompanied by diuresis. Glycerol-containing beverages create an osmotic gradient in the circulation favouring fluid retention, thereby facilitating hyperhydration and protecting against dehydration. Many studies have shown that increases in body water by 1 L or more are achievable through glycerol hyperhydration. This article analyses the evidence for glycerol use in facilitating hyperhydration and rehydration, and provides guidelines for athletes wishing to use this compound. An analysis of the studies in this area indicates that endurance athletes intending to hyperhydrate with glycerol should ingest glycerol 1.2 g/kg BW in 26 mL/kg BW of fluid over a period of 60 minutes, 30 minutes prior to exercise. The effects of glycerol on total body water when used during rehydration are less well defined, due to the limited studies conducted. However, ingesting glycerol 0.125 g/kg BW in a volume equal to 5 mL/kg BW during exercise will delay dehydration, while adding glycerol 1.0 g/kg BW to each 1.5 L of fluid consumed following exercise will accelerate the restoration of plasma volume. Side effects from glycerol ingestion are rare, but include nausea, gastrointestinal discomfort and light-headedness. In summary, glycerol ingestion before, during or following exercise is likely to improve the hydration state of the endurance athlete.Keywords
This publication has 84 references indexed in Scilit:
- Drinking guidelines for exercise: What evidence is there that athletes should drink “as much as tolerable”, “to replace the weight lost during exercise” or “ad libitum”?Journal of Sports Sciences, 2007
- Exploring the Potential Ergogenic Effects of Glycerol HyperhydrationSports Medicine, 2007
- Heat Illness in AthletesSports Medicine, 2004
- Fluid and electrolyte needs for preparation and recovery from training and competitionJournal of Sports Sciences, 2004
- Fluid and fuel intake during exerciseJournal of Sports Sciences, 2004
- Pre-exercise carbohydrate and fat ingestion: effects on metabolism and performanceJournal of Sports Sciences, 2004
- GlycerolSports Medicine, 1998
- Assessing the quality of reports of randomized clinical trials: Is blinding necessary?Controlled Clinical Trials, 1996
- Sustained hyperhydration with glycerol ingestionLife Sciences, 1995
- Effect of primary hypohydration on physical work capacityInternational Journal of Biometeorology, 1988