We see ice slushies used mainly in high-heat events such as the Tokyo Olympic Games or the Tour de France. It is used for pre-cooling before a race, during cycling, and after competing to reduce core temperature. First, let’s see what happens in your body when you ingest an ice slushie.
Why are ice slushies much more effective than cold water?
When you drink something cold, your body uses some of its heat energy to warm it up, which slows the overheating process during exercise. The thing about slushies is that the energy required to turn ice into a fluid is 80 times as high as the energy required to heat up cold water. This is why slushies can cool cyclists much faster and much more than regular cool drinks. The only problem is that this activates thermoreceptors in the abdomen, which leads to a reduction in sweating. Sweating is the most effective method of cooling so losing it is not a good trade-off. Let’s see what experiments have shown so far.
Using slushies before a ride
One way to solve the problem with reduced sweating is to consume the ice slush before the ride where there is no sweating anyway. Studies show this can reduce body temperature by approximately 0.5°C. Reducing body temperature makes cyclists able to ride for longer before reaching a core temperature, at which exhaustion occurs. This approach also has its risk. Consuming too much slush before a ride can cause digestive issues and if the core temperature falls too much, performance is negatively impacted too.
Using slushies during a ride
When it comes to slushie use during exercise, studies show that it doesn’t bring much of a benefit if the surrounding temperature is mild, around 25°C. However, when the conditions are hot (>32°C) and humid, which a lot of cycling races are, it’s a different story. Controlled experiments under these conditions have shown a reduction in core temperature and even improved performance. This is likely because, at very high temperatures and humidity, sweating becomes less effective at cooling, which reduces the downside of using ice slush.
How should you use ice slushies?
Unfortunately, cycling is not the best sport for ice slush use. Cyclists cut through the air at high speed, which helps sweat evaporate and improve its cooling efficiency. When sweating efficiency is high, slushies offer almost no benefit. Ice slushies would only be beneficial on the bike in extremely hot and humid environments for athletes with a very high sweat rate. Their main use case scenario in cycling is for pre-cooling before a race. If you are able to get your hands on a blender or a slushie machine before the start line or a hard ride on a hot day, go for it! Otherwise, sweating is your best way to cool down.