When it's so hot that endurance athletes lose more than 3-4 percent of their bodyweight in liquid, their performance declines. What can help is hyperhydration: raising the level of hydration in advance. Nutritionists at the University of Glasgow studied the effect of hyperhydration using a ****tail of creatine and glycerol.
Hyperhydration is a little more complex than just making sure you drink lots of water. That doesn’t work: the extra liquid leaves the body at high speed via the urine.
What does work is drinking water to which a substance is added that helps the body to retain the extra liquid for longer. A tried and tested strategy is to add creatine and glucose. [Int J Sport Nutr Exerc Metab. 2004 Aug; 14(4): 443-60.] If you consume 10 g creatine twice a dag for a week, the amount of water in your body increases by 400-800 g. It works best if you consume the creatine together with carbohydrates; this way your body absorbs one and a half times as much creatine.
Another strategy is to drink water containing glycerol. [Int J Sport Nutr Exerc Metab. 2002 Mar; 12(1): 105-19.] Four hours before you start training you consume 1-1.5 g glycerol per kg bodyweight mixed in 1.5 – 2 litres of water. This also results in an increase of 400-800 g liquid reserves.
In 2007 sports scientists discovered that you can combine the two strategies. [Int J Sport Nutr Exerc Metab. 2007 Feb; 17(1): 70-91.] This is also the approach that the researchers in Glasgow adopted. They gave 15 male long-distance runners 10 g creatine and 1 g glycerol per kg bodyweight together with 75 g of a glucose polymer, twice a day for a week.
This led to a weight increase [BM] of 0.85 kg in the athletes. Most of this weight increase consisted of water [TBW].
After a week, the test subjects were first made to cycle for half an hour at 10 degrees Celsius at 60 percent of their VO2max. Afterwards they had to cycle for another half hour at the same intensity, but the temperature was 35 degrees Celsius. The humidity of the air was kept at a constant 70 percent.
During the session at 10 degrees the hyperhydration [white circles] had no effect. During the session at 35 degrees the hyperhydration resulted in a lower heart rate [HR], a lower body temperature [Tcore], and less fatigue [RPE]. The researchers detected no effect on maximal oxygen uptake or nutrient burning. This may be because the intensity and length of exertion were on the modest side.
Although you might think from the results that hyperhydration can help endurance athletes to perform better at summer temperatures, the researchers do not draw this conclusion. Some studies show that there is a positive correlation between the amount of moisture that endurance athletes lose during races and their performance. One theory is that the weight loss makes movement less of an effort and therefore boosts performance. [J Sports Sci. 2004 Jan; 22(1): 39-55.] If this theory holds water, what use is hyperhydration to endurance athletes? None.
The researchers argue that follow-up studies are needed.
J Int Soc Sports Nutr. 2011 Dec 16;8(1):24.