• It is generally not advisable to run - without training - "in the wild", according to our partner The Conversation.

  • However, this can be done by learning to hydrate well and by getting your body used to the temperature (which can take up to 14 days!).

  • Analysis of this phenomenon was conducted by Hannah Moir, Senior Lecturer in Exercise and Health and Chris Howe, Researcher and Engineer (both at Kingston University - London).

Summer is a good time to exercise outdoors, to take advantage of milder - if not scorching, temperatures.

Beyond the pleasure of being outside in the sun to train, you must also be wary of the heat ... The Directorate General of Health has also set up a telephone information platform that allows you to obtain information. tips to protect yourself.

But what are the consequences of these high temperatures for runners?

Running enthusiasts can legitimately wonder if they are taking risks by putting on their trainers when it is over 30 ° C.

However, there is nothing exceptional about running in hot weather: in Kenya, Ethiopia and Japan, many professional runners train regularly when it is 25 ° C on average.

In fact, while running in very hot weather poses risks for some people - children, the elderly, and pregnant women - as long as you take certain precautions, it is okay to run when the weather is hot. temperatures are between 30 to 35 ° C.

Moreover, a number of races take place in extremely hot conditions (over 35 ° C).

This is the case of Badwater, the 217 km ultra-marathon that takes place in Death Valley, California, where temperatures can reach over 50 ° C in the shade.

There is also the Marathon des Sables, a five-day race in the Sahara Desert in Morocco, where temperatures also hover around 50 ° C.

This 240 km race is considered the most difficult race there is.

The Marathon des Sables © Cimbaly_MDS2019 / JOSUEFPHOTO

Our experience at Kingston University with people training in a heated room - for events such as the Marathon des Sables and Badwater - shows that with sufficient preparation, proper hydration and listening to your body, it is possible to run even if it is very hot.

But it should be kept in mind that these races require specific preparation, especially in terms of acclimatization to the heat, and it is strongly recommended not to attempt the adventure without extensive and specific training.

Prepare yourselves !

Running in 30 ° C is not without its risks, and can very easily cause dehydration and overheating of the body, leading to cramps, excessive sweating, headaches, nausea, fatigue and dizziness. The heat can also affect your athletic performance: it may prevent you from running at the same pace and covering the same distances as when the temperatures are lower. There are still other health risks, ranging from exhaustion to heat stroke.

But these symptoms can be avoided if you listen to your body and take precautions to avoid suffering from the heat: drink enough to stay hydrated, avoid running during the hottest hours of the day (between 11 a.m. and 3 p.m.), wear light and "breathable" clothes, slow down your pace, and finally take into account that your body has to get used to the temperature (which can take up to 14 days).

Running in 30 ° C is not without risks © Maarten Van den Heuvel / Unsplash

The body learns to adapt

Running in very hot weather causes normal body temperature to rise.

Indeed, the body functions best when its core temperature is maintained at 37 ° C;

perspiration helps maintain this temperature, letting the heat evaporate.

But it also causes a loss of water contained in the blood, which can lead to dehydration.

To help the body to sweat, the blood vessels dilate so that more blood circulates on the surface of the skin.

It is for this reason that we blush and our blood vessels are more visible when it is very hot.

The downside is that there is less blood available to supply the muscles during full effort, which puts a strain on the body - and especially the heart -.

The hotter it is, the more dependent we are on sweating to keep our bodies at a normal temperature.

When you exercise in hot weather, you can lose 1 to 4 liters of sweat.

Our file "RUNNING"

However, compared to many animals, humans are particularly good at regulating their body temperature, which allows them to run long distances in spite of the heat.

By regularly exposing itself to high temperatures, the body learns to endure the inconveniences associated with heat and these are reduced.

The body adapts by sweating more, by increasing blood volume, and by reducing the loss of electrolytes (important salts and minerals) via sweating.

Body temperature drops (at rest or during exercise), while the heart rate slows and the level of perceived exertion drops.

So, with the right preparation and a little common sense, you can run safely, even when the thermometer is going crazy!

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This review was written by Hannah Moir, Senior Lecturer in Exercise and Health and Chris Howe, Researcher and Engineer (both at Kingston University - London).


The original article was translated and published on The Conversation website.

Declaration of interests

The authors do not work, do not advise, do not own shares, do not receive funds from an organization that could benefit from this article, and have not declared any affiliation other than their research organization.

  • Global warming

  • Sport

  • Heat wave

  • Running

  • Video

  • The Conversation

  • Health