Keeping cool in the heat July 21 2015, 0 Comments

One of the reasons that we are a successful species when it comes to running is our ability to sweat.

When it evaporates, water takes energy from nearby heat sources to increase the energy of its molecules enough to launch them into the air. The energy used to change the state of the water from liquid to vapour is called the latent heat of vaporisation. When the latent heat is taken from our bodies, it has a cooling effect. In contrast to animals such as dogs who cannot sweat, and have to cool themselves by panting, this means that our whole body surface can be used to cool us, which is why we are so good at running long distances. Dry atmospheric heat is better for us than humid heat, - you are more sweaty in humid heat because the sweat stays on your skin and does not evaporate as easily, so the cooling effect is reduced. Wiping sweat off can be counterproductive, as it can no longer evaporate and cool.

So what does that mean for running in the heat? Essentially, you should aim to expose as much skin as possible to allow evaporation (don't forget to use suncream...), and/or use clothing which wicks the sweat away from your body to the outer surface of the cloth so that evaporation can still take place.

The second part of this story is equally important - because you are losing so much liquid from your skin, you need to drink frequently to restore it. You also lose minerals (notice how your sweat tastes salty), and you will need to replace these. Omission of either of these can result in heat exhaustion; lack of water causes excessive thirst, weakness and headaches; lack of minerals causes nausea, vomiting, muscle cramps and dizziness. So keep drinking, and in hot weather consider upping the amount of salt that you put on your food, or address both with balanced salt drinks.