Canadians are used to exercising in extreme weather conditions from -30 to +30C. Right now, we’re at the hot weather extreme. It likely comes as no surprise that hot weather compromises exercise. To help cool the body, blood must go to the skin. However, there is a dual requirement as blood flow to muscle is also necessary for the working muscle during exercise. The brain will downregulate muscle recruitment when exercising in hot conditions so that athletes self-select a lower intensity. 

To help counteract this, many high level athletes incorporate techniques, such as wearing a cooling vest, to cool their body before exercise. If you watched the 2004 Olympics women’s marathon, you likely saw Deena Kastor doing this. Starting exercise with a lower core temperature allows athletes to better tolerate heat. However, the average runner is not likely going to have a cooling vest, but there is a simple and cheap alternative- what you drink before exercise.

Consuming an ice slushy prior to the start of exercise has been shown to improve performance by reducing core body temperature just like a cooling vest would. This can be achieved with consuming a relatively small volume (500-600 ml) of an ice slushy. Interestingly, providing cool fluids during exercise rather than before exercise doesn’t show the same performance impact. It’s specifically pre-exercise that is importance so that you’re starting off with a lower body temperature. However, this performance may also be caused by a brain cooling mechanism, such that receptors in the brain are being activated so that you’re able to raise your body temperature to a higher level.

Consuming an ice slushy prior to exercise in hot environments not only improves performance but has few side effects beyond a brain freeze. Got an upcoming exercise bout planned for a hot day? Crush up a couple cups of ice to make your own ice slushy to cool yourself down before you head out the door! 

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Categories: Megan Kuikman

Megan Kuikman

Hello! I’m Megan Kuikman. I’m a Registered Dietitian with specialized training in sports nutrition. My goal is to help athletes and active individuals achieve a healthy attitude towards health, training, and food. I empower athletes to fuel properly for training in order to restore their health and enhance performance. You can get in touch with me at:


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