Outdoor sport in times of COVID-19 - safe or not

If you want to walk, cycle, jog outside, you must take into consideration that there is different safe distance you have to keep

Photo: KU Leuven (Belgium); TU Eindhoven A clear example of the cloud of droplets left behind by a person, who is running, walking or cycling.

Because of the urgency of the situation and the world‐wide COVID-19 crisis, we exceptionally have turned things upside down, even though in a lot of countries walking, biking, cycling and jogging are still welcome activities. However, it is important to note that you need to avoid each other's slipstream when doing these activities. 

Still, what is a safe distance when running, biking and walking during COVID-19 times? It is further than the typical 1–2 meter as prescribed in different countries!The finding is part of a study, conducted by by the KU Leuven (Belgium) and TU Eindhoven (Netherlands).

Yes, the typical social distancing rule which many countries apply between 1–2 meters seems effective when you are standing still inside or even outside with low wind. But when you go for a walk, run or bike ride things are quite different. When someone during a run breathes, sneezes or coughs, those particles stay behind in the air so the person running behind you in the so-called slip-stream goes through this cloud of droplets.

The researchers came to this conclusion by simulating the occurrence of saliva particles of persons during movement (walking and running) and this from different positions (next to each other, diagonally behind each other and directly behind each other). Normally this type of modelling is used to improve the performance level of athletes as staying in each other air-stream is very effective. But when looking at COVID-19 the recommendation is to stay out of the slipstream according to the research.

As you can see in the number of animations and visuals, the cloud of droplets left behind by a person is clearly visible. “People who sneeze or cough spread droplets with a bigger force, but also people who just breathe will leave particles behind”, as the authors of the study show. The red dots on the image represent the biggest particles. These create the highest chance of contamination but also fall down faster.

“But when running through that cloud they still can land on your clothing” according to Professor Bert Blocken from 

Interestingly, out of the simulations, it appears that social distancing plays less of a role for 2 people in a low wind environment when running/walking next to each other. The droplets land behind the duo. When you are positioned diagonally behind each other the risk is also smaller to catch the droplets of the lead runner. The risk of contamination is the biggest when people are just behind each other, in each other’s slipstream.

On the basis of these results the scientist advises that for walking the distance of people moving in the same direction in 1 line should be at least 4–5 meter, for running and slow biking it should be 10 meters and for hard biking at least 20 meters. Also, when passing someone it is advised to already be in different lane at a considerable distance e.g. 20 meters for biking. 

More on this subject: Coronavirus

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