Glycerol Guide

Submitted by Guest
Wednesday, August 19, 2009

Glycerol loading is currently a hot topic among sports scientists with an interest in endurance events. But what is it? Read on and all will be explained…

When exercising, your body sweats to keep your core temperature within a controlled range. If you sweat more, you’ll stay cooler – but if you sweat too much, you’ll dehydrate, which is both dangerous and detrimental to your athletic performance.
 
So far, so obvious. But what if you could increase your body’s ability to store water before a race, and as a result provide you with greater reserves with which to sweat, before you started to dehydrate? That's what glycerol loading is all about.
 

The syrup

Glycerol, also known as glycerin, is a rapidly absorbed, natural, well-tolerated liquid with a syrupy consistency. It’s highly hydroscopic; that is, it drags extra water into all the body’s cells. Its primary use is in medicine, food and cosmetics. Outside these areas, military research found a specific glycerol and water- loading regime (GWL) caused a two-hour ‘load-up’ and a two-hour period of reduced urine output while at rest. This GWL added around 750ml of water to body water stores, reducing body temperature and raising sweat rate during exercise in hot conditions.
 
The British Olympic Committee published a secret paper on GWL just prior to the Barcelona Olympics saying it “keeps the outer surface of the body cooler, maintains cardiac output and delays the onset of fatigue”. Better still, recent research on triathletes competing an OD race showed that GWL helped athletes complete the race 10mins faster than those on a sports drink load-up.
 

How to beat the heat

The mechanism is simple: drink an exactly-mixed glycerol and water solution around 150mins prior to a hot race. Get it right and you’ll enjoy better tolerance to exercise in the heat while others wilt. Ideal distance for optimum effect remains unclear but is likely to be OD upwards.
Negative effects are uncommon but some people report bloating, so try it out before an important race. But don’t just drink a random amount: it needs to be exact (see table, below).
 
The critical level where fluid loss affects performance again is not clear-cut. Some have suggested 2% loss equals 10% performance loss; other data suggests up to 3 or even 5% fluid loss can be tolerated. Evidence suggests, though, that endurance performance is improved around 1-4% when using GWL, compared to just drinking lots of water pre-event. Not bad for just a few pence per load-up. So if you’ve scheduled some warm-weather training and/or racing this season, GWL could be your secret weapon.
 

 

How to take glycerol

Step one

Calculate water and glycerol needs based on your bodyweight (bw). Each drinking period shown below requires 5ml/kg/bw* of water. For example, a 70kg person needs 350ml each time (5 x 70). The glycerol (1ml/kg/bw) is only used in the first drink, though. So the 70kg person would use 70ml glycerol. All subsequent drinks are water-only beverages.

Step two

Mix the glycerol (1ml/kg/bw) with the first dose of water (5ml/kg/bw) to make a 20% concentration of glycerol that begins the glycerol load-up. This must be consumed 150mins before exercise. Once this glycerol drink has been consumed, the remaining four amounts of water must be drunk. Glycerol requires 25 times its weight in water or severe dehydration can result.

Step three

Drink remaining water-only solutions as per the table below. If you wish to drink further water/sports drinks between the last required drinking time (T-60, 1hr before the race) and race start time, that is okay.

 

NOTE Diabetics, pregnant women or those with high blood pressure or kidney disorders should seek medical advice before considering glycerol hyperhydration.