Glycerol

Glycerol (also referred to as glycerine) is a three-carbon simple lipid that is metabolized like carbohydrate. The three-carbon structure of glycerol holds dietary fatty acids together to form triglycerides. Glycerol is a powerful humectant, with a potent capacity to attract a large volume of water. A number of endurance athletes use glycerol as a means of superhydration because of this capacity to hold water, as well as glycerol's ability to be easily and cleanly metabolized for energy. Adding a small amount of glycerol to water enables an athlete to store more water and, in doing so, may aid the athlete in endurance competitions that take place in extremely hot and humid environments.

Maximizing body water may induce a level of stiffness that some athletes find uncomfortable. Indeed, athletes who consume glycerol-laced fluids before an event often complain that they feel, at least initially, stiff and sluggish. But many of these same athletes claim that the benefits of having extra water at the end of a race far outweigh the feeling of sluggishness at the beginning of the race. While other athletes are dehydrated and overheating, these athletes say they feel more fresh when it counts the most.

A word of caution: Although many endurance athletes use glycerated water to enhance their hydration state, this product has never been adequately tested for safety. Because glycerol is a normal component of the diet and is easily metabolized, it is unlikely that small amounts of glycerol, by itself, would cause any difficulty. With higher doses, headaches and blurred vision may occur.Furthermore, it is unclear how much additional stress is placed on the cardiovascular system when additional water is stored in the system.

The IOC bans diuretics because of the detrimental effects of dehydration and because diuretics have been used to lower the concentration of biological markers of steroids and other banned substances in the urine. Glycerol was once classified as a diuretic, but in 1997 the U.S. Olympic Committee (USOC) removed the ban on glycerol because it was widely understood that diuresis is not likely at glycerol doses of between 1.0 and 1.5 grams per kilogram.

There is no widespread consensus on how to best consume glycerated water. The protocol established for a 155-pound (70 kilogram) athlete ingesting approximately 2 liters of fluid 2.5 hours before activity is as follows;

• Drink 5 milliliters per kilogram of a 20 percent glycerol solution.
• Thirty minutes later: Drink 5 milliliters per kilogram of water.
• Fifteen minutes later: Drink 5 milliliters per kilogram of water.
• Fifteen minutes later: Drink 1 milliliter per kilogram of a 20 percent glycerol solution and 5 milliliters per kilogram of water.
• Thirty minutes later: Drink 5 milliliters per kilogram of water.
• Begin exercise 1 hour later.

For events lasting more than 2 hours, consuming 400 to 800 milliliters per hour of a 5 percent glycerol solution before and during the event may also be beneficial, although there is more compelling evidence that consumption of a 6 to 8 percent carbohydrate solution during competition is ergogenic.