A cold drink to exercise in the heat?

Could consuming cold drinks or ice slush during workouts in the heat help you to perform better? Scientists have been wondering this for many years.

Theoretically it makes sense: as your brain’s main objective is to keep you safe, it will force you to slow down or even stop if it presumes that your core temperature could increase to dangerous levels before the end of the workout. Anything that helps you to keep your core temperature down is thus beneficial, and as cold drinks could act as a heat sink they could be helpful indeed. Scientific studies however, have been inconclusive.

© Dnally | Dreamstime Stock Photos
© Dnally | Dreamstime Stock Photos

Florence Riera and her colleagues have just published the latest study about this problem in PlosOne. They compared the effects of a cold (3 C), ice slush (-1 C) or neutral drink (23 C) with or without menthol flavouring on the performances of 12 trained male cyclists in hot and humid conditions.

The cyclists were randomly assigned a beverage and performed a 20 km time trial in the lab, which means that each of them did the test 6 times (once with each beverage). The performance was better using ice slush whatever the aroma, and better with menthol whatever the temperature. Ice slush or cold water with menthol flavouring was therefore the best.

The researchers concluded that a cold or ice slush drink interferes with the rise in core temperature, allowing you to exercise harder without – or with a smaller- increase in core temperature. 

Menthol usually provokes a sensation of freshness, it is a bit stimulating and it improves the airflow (that is why you use menthol lozenges when you have a cold), but exactly how it works is unknown.

Drinking ice slush is probably possible when you are cycling on a turbo trainer or in the gym, but what can you do if you are a road cyclist? You could try to cool down your core in advance, and researchers have shown that ice vests or cool water baths are helpful indeed.

Pre-cooling techniques are usually unavailable for recreational athletes, but cold drinks can easily be obtained before the start of any event. Christopher Byrne and his colleagues therefore wanted to find out if you could pre-cool yourself with cold drinks.

Seven male cyclists ingested 900 ml cold (2 C) or neutral (37 C) water over 35 minutes before cycling as many kilometres as possible for 30 minutes in a lab. When the athletes drank cold water they cycled 2.8% further and their core temperature (as estimated by rectal temperature measurements) was lower at the end of the test. They felt really cold before starting off though, and one of them was even shivering. Most of them needed to urinate before the exercise. Probably not a very pleasant experience….

© Denise Scott Jackson | Dreamstime Stock Photos
© Denise Scott Jackson | Dreamstime Stock Photos

I wonder if this kind of pre-cooling is possible for runners, as such a large amount of fluid is likely to create gastro-intestinal discomfort? I guess that the only thing runners can do is to get acclimatised and to accept that we will be slower…Or do you have a better idea?

References

C Byrne, C Owen, A Cosnefroy et al. Self-paced exercise performance in the heat after pre-exercise cold-fluid ingestion. J Athl Train. 2011; 46(6): 592-599.

 F Riera, TT Trong, S Sinnapath et al. Physical and perceptual cooling with beverages to increase cycle performance in a tropical climate. PLoSONE 9(8): e103718. doi:10.1371/journal.pone. 0103718. (Accessed 09/08/2014).

R Tucker. The anticipatory regulation of performance: the physiological basis for pacing strategies and the development of a perception-based model for exercise performance. Br J Sports Med 2009; 43: 392-400.

 Disclaimer: this article is for general information only, and does not replace medical advice. It cannot be used to diagnose or guide treatment. If you have any concerns or questions, you should talk to a qualified health provider.

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