Beat the heat with iced drinks

After the coldest spring for more than 50 years, most cyclists will be looking forward to some warm weather this summer. However, warm-weather riding can bring its own set of problems.

It’s not just the risk of dehydration from sweating, which can severely hamper your cycling performance – staying cool is important too because even a small rise in your body’s core temperature can adversely impact how long and how hard you can ride.

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The use of appropriate cycling garments and taking plenty of drinks can help of course, but once the mercury climbs, it’s hard to avoid at least some degree of heat build-up. That’s where ice slurry drinks come in since it takes large amounts of heat (absorbed from the body) to turn ice at 0°C to water at 0°C, more technically known as the ‘latent heat of fusion’.

A brand new Australian study indicates that cyclists could take advantage of this law of physics to improve performance.

The science
In the study, researchers investigated the effect of consuming ice slurry drinks during the cycling leg of a triathlon in hot conditions. Nine well-trained male triathletes performed two randomised trials of a simulated Olympic distance triathlon in temperatures of 32-34°C.

Exercise intensity during the swim (1,500m) and cycle (one hour) legs was standardised, but the 10km run leg that followed was a self-paced time trial during which the subjects ran the distance as fast as they could.

During the cycle leg of each trial, the subjects drank either 10g per kilo of bodyweight of ice slurry or the same amount of the same type of fluid at room temperature (32-34°C).

The researchers wanted to see whether ice slurry drinks were more effective than room temperature drinks at lowering the temperature in the stomachs of the subjects. They also looked at how the different drinks affected the subjects’ perceptions of heat stress and (importantly) what effect the drinks had on subsequent performance.

In a nutshell
The results were pretty convincing. When the triathletes drank the ice slurry, their subsequent performance in the run leg was significantly faster – an average time of 43.4 minutes when ice slurry was consumed versus 44.6 minutes when room temperature drinks were taken.

This effect was very noticeable during the last 0.5km of the run when the subjects’ oxygen consumption levels (and therefore power outputs) were nearly 10 per cent higher when ice slurry was consumed. Also, drinking the ice slurry resulted in lower levels of perceived thermal stress by the subjects.

So what?
The researchers concluded that the consumption of ice slurry resulted in a less steep rise in stomach (and therefore core) temperatures, which had reduced the perceived heat stress and allowed the triathletes to work harder during the running leg.

Although this was a triathlon-based study and runners are more prone to overheating than cyclists, there’s no reason to believe that this hot- weather strategy wouldn’t be of benefit in cycling-only events too. In cooler conditions, a nice cool drink without ice is likely to suffice just as well!
J Sports Sci. 2013 Mar 18. [Epub ahead of print]

This article was first published in the May 16 issue of Cycling Weekly. Read Cycling Weekly magazine on the day of release where ever you are in the world International digital edition, UK digital edition. And if you like us, rate us!