Saturday, May 31, 2014

Hot Drink Cools You Faster Than A Cold Drink?

Picture by Hogansville Coffee Co from Flickr
Really? Sure or not? That was my exact first reaction when I was saw this article. On second thought, I definitely do recall seeing all the ah peks (or elderly men for my overseas readers) sipping a hot coffee/ tea while sitting beneath a ceiling fan in our neighbourhood coffee shops in the sweltering heat.

Many past studies point to the very obvious fact that cold drinks lower your core temperature more than hot drinks. It now appears these previous studies used a flawed method to measure core temperature.

Under certain circumstances, a hot drink really does cools you more than a cold drink. Please read on to find out how this can help you exercise or race better in hot conditions.

The researchers in the study had their subjects perform a series of moderate effort cycling in their lab while drinking water at 1.5, 10, 37 or 50 degree celsius.

Unlike other studies using just a rectal thermometer to measure core temperature, the researchers used eight different thermometers on various body parts plus a rectal thermometer and another inserted through the nose down to the oesophagus to get a much more accurate reading.

Rectal thermometer??!! I don't know about you, I definitely will not volunteer for this study if I have to stick a thermometer inside my butt.

A rectal thermometer alone may register a lower temperature if you drink a large glass of ice water since the rectal thermometer measures the cold drink in your stomach (even though the rest of your body may not have cooled).

Sweating is the most effective tool your body has to get rid of excess heat. The study found that drinking hot water triggered a sweat response that more than compensated for the heat of the drink.

Cold drinks on the other hand produced the opposite response, a reduction in sweat cancelling the cooling power of the cold drink.

Does this mean you should drink a hot drink on a hot day to cool off? Well, the only caveat is your sweat must fully evaporate in order to produced the desired cooling effect. If you are exercising hard, or in a super humid environment (like in Singapore where it's often in excess of 90% humidity), you may sweat more than the sweat can evaporate. No point sweating more then. If your extra sweat just drips onto the floor then you're better off drinking a cold drink.

How does this information help you perform better in your race here in Singapore? The authors suggests ingesting a slushie before your exercise or race as this definitely produces a measurable drop in your core temperature as heat from your body is drawn to transform a solid (the ice in your slushie) to a liquid (water).

Picture of slushie by wwerewolf from Flickr

Bain AR, Lesperance NC and Jay O. (2012). Body Heat Storage During Physical Activity Is Lower With Hot Fluid Ingestion Under Conditions That Permit Full Evaporation. Acta physiologica. DOI: 10.1111/j.1748-1716.2012.02452.x

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