Strenua's World

Investigating the training, treatments, diets and science behind a healthy active life

Chill as you rehydrate to improve endurance

Posted on June 02nd, 2009 in Drink, Exercise, Science, Training

water-bottle With summer arriving and temperatures rising, it’s even more important than ever that you take out your drinks bottles when you are training or competing.

We all are aware that dehydration through sweating can compromise athletic performance. Evaporating sweat from the skin surface is the body’s way of regulating our core body temperature, essential whilst exercising in this summer heat. Unfortunately if our sweat loss exceeds fluid intake we can become dehydrated, this is increased if you are involved in intense exercise, in a hot, humid environment. Dehydration of just 1-2% of body weight begins to compromise physiological function and negatively influence performance. However you should drink according to individual needs and not on published recommendations as hyperhydration can be as dangerous as dehydration. I shall write more about how to determine your own personal fluid intake in a later article.

You probably have your own personal favourite drink when training or competing, whether it’s a manufactured sports drink, your home made recipe, or just plain water. But have you considered the effect the temperature of the drink may have on your performance?

In the journal Medicine & Science in Sports & Exercise,researchers from Loughborough University investigated the effect of drink temperature on cycling capacity in the heat. The two groups of males cycled to exhaustion in hot (35^oC) and humid (60%) environments. The subjects drank three 300-mL volumes of either a cold (4^oC) or a warm (37^oC) drink during 30 mins of seated rest before exercise and 100 mL of the same drink every 10 mins during exercise.

They found that compared to the warm drink, drinking cold drink resulted in:

Longer exercise time – (64mins with cold 52 mins with warm).
Lower mean skin temperature after 20 mins during exercise.
Lower heart rate before exercise and for the first 35 min of exercise.
Reduced sweat rate (1.22 L/hr for the cold and 1.40 L/ hr with the warm drink).
Lower perceived exertion during exercise.
There was no effect of drink temperature on mean skin temperature at rest.
Overall improved endurance capacity of around 23%.

Author of the paper, Dr Jason Lee, concluded that compared with a drink at 37^oC, the ingestion of a cold drink before and during exercise in the heat reduces physiological strain during exercise due to reduced heat accumulation.

Obviously keeping your drink at 4^oC isn’t practical if you have to carry it as you run or cycle, but how about keeping your drink in the fridge before you start exercising. During exercise you can make sure it’s kept in the shade or a bucket of iced water, if you are playing sport in a fixed location. I also like to put my drink in the freezer before I go out. Not enough for the drink to freeze solid but enough to allow a few ice crystals to form to keep it chilled for longer. If I can make my endurance capacity increase by 23% just through the temperature of my drink, I think this is one suggestion I’m going to try to incorporate in my running this summer.

Do you have any suggestions how to keep you drink colder, for longer whilst exercising during the summer? If so let us know.