Decrease Risk of COVID-19 Transmission by Avoiding Slipstreams While Walking, Biking, and Running


With gyms closed and walking outside amongst the only activities still allowed during our Shelter-in-Place order, it seems as though more South Florida residents are heading outside to get in their daily walks and workouts. Getting outside in the beautiful weather can undoubtedly be beneficial to our mental and physical health, but a recent white paper released by researchers at KU Leuven and Eindhoven University of Technology encourages us to be cautious with our social distancing by avoiding other people’s slipstreams while walking, running, and cycling.

Please note that this research has come under scrutiny from the scientific community because it has not yet been peer-reviewed, was not conducted by virologists, and does not consider viral load. 

The Belgian and Dutch researchers found that while staying 6 feet apart is “very effective for people who stand still indoors or outdoors in calm weather,” when you are walking, running, or cycling outdoors, you risk entering into a cloud of microdroplets from another person’s slipstream, which is what researcher Bert Blocken, professor of civil engineering at Eindhoven University of Technology and KU Leuven, defines as “the zone that arises right behind a person when they are walking or cycling, and which pulls the air a bit along with this moving person." 

The research was conducted by simulating the release of saliva particles from people walking and running in different configurations e.g. two people side by side, diagonally behind and right behind each other. 

The researchers found that:

  • The risk of contamination is greatest when people walk or run closely behind each other and therefore in each other's slipstream.
  • Social distancing plays less of a role for two people who walk or run side by side in calm weather. The drops then end up behind the duo. 
  • Those who move in a staggered arrangement are also less likely to catch saliva droplets from the predecessor, at least when there is no substantial cross‐wind. 

Their findings have been visualized in this simulation video tweeted by Professor Blocken. Based on the results of this simulation, the researchers offer the following advice:

  • Keep a distance of at least ~13ft 1.5 inches to ~16 feet, 5 inches (4 to 5 meters) while walking behind someone in their slipstream.
  • Keep a distance of at least ~32 feet, 10 inches (10 meters) while running or cycling behind someone in their slipstream.
  • Keep a distance of at least ~65 feet, 7.5 inches (20 meters) when cycling fast behind someone in their slipstream.
  • If you want to overtake someone while cycling, start staggering from a long distance of ~65 feet, 7.5 inches (20 meters).

Along with the criticism, many people have used this white paper to question the safety of running, walking and biking outside altogether. An April 8 tweet by researcher @bertblocken attests that: “Cycling & running are not big risks for #COVID19 spread. But moving closely in slipstream is. This holds everywhere, also when walking in supermarkets, shops, etc. No need at all to ban running or cycling. #COVID #coronavirus.”

As of now, nothing has changed in the national recommendations for social distancing, even while heading outside to stay active. This research might make you consider being extra conscientious of your social distancing, by avoiding other people’s slipstreams, while getting in your outdoor workout. 

Read the full white paper here.

Jacqui Somen is a health & wellness writer, NASM certified personal trainer, and certified pre and postnatal fitness specialist. Follow her at @vivamafit.

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