When you meet people who ride bicycles and run on the road, you may be vigilant, and even maintain a social distance of more than 1.5 meters.
Because a new study says that the cough or breath droplets of cyclists and runners can be spread farther.
Recently, a research team from Belgium and the Netherlands released an unpeer-reviewed research report saying that cyclists and runners should be extra careful when passing others, and warn them that droplets spread through the respiratory tract may reach 1.5 Meters away.
Generally speaking, unpublished research reports will not attract widespread attention.
But a researcher in this report, a professor of civil engineering from the Eindhoven University of Technology in the Netherlands, and also a professor at the University of Leuven, Belgium, accepted media interviews and published the results of the research report via Twitter.
In a special period of time, he published the research results publicly. Blocken expressed that he hopes to directly lead the discussion of the peers and share the results, because it may immediately play a role.
After dissemination through the Internet and the media, this research report, which has not been peer-reviewed and accepted by scientific journals, has caused some controversy because the research has caused panic. In some areas, government departments have banned bicycling and running.
What conclusion did this study draw?
So, what did the study say? According to the preprint paper published by the research team, Bate Blocken is the first author. Previously he published research on the diffusion of pollutants in urban environments and the thermodynamic flow around wind turbines.
In this research on the new coronavirus pneumonia, Blocken and his team entered the wind tunnel at Eindhoven University to measure the air flow around running and cyclists at three speeds: normal walking speed, fast running and Moderate bicycle speed. Although the research team did not calculate what would happen in crosswind, headwind, or tailwind throughout the test, it considered the effects of droplet evaporation.
They then combined the data with existing research on how respiratory droplets spread during exercise. It should be noted that the study did not attempt to estimate the risk of exposure to infection during exercise, but only described the flow of droplet particles in the air.
Above a distance of 4.5 meters, when running at a speed of 4 meters per second, the air velocity profile in the vertical center plane.
After calculations, the research team concluded that cyclists and runners must be more than 1.5 meters away from other people to prevent others from inhaling droplets or falling on them.
The team also calculated the safe distance for each sport: when riding at a speed of 18 miles per hour (1 mile is approximately equal to 1.6 kilometers), you need to maintain a distance of 65 feet (equivalent to 19.8 meters) and a speed of 6 minutes per mile 44 When running at a rhythm of seconds, you need to maintain a safe distance of 33 feet (equivalent to 10 meters), and when you walk at normal speed, you need to maintain 16 feet (equivalent to 4.9 meters).
Blocken said that beyond these safe distances, the droplets have already reached the ground and will not fall on the faces of passers-by.
As for side-by-side cycling or jogging, Blocken said that unless it is exactly the direction of the cough of the virus carrier, otherwise the problem is not great.
Illustration of droplet spread in three running modes
The wind tunnel test concluded that the potentially hazardous area fell in a narrow slipstream behind runners and cyclists, rather than forming a large V-shaped cone.
Blocken said that in theory, this means that runners or cyclists can avoid slipstream infections by staggering the virus.
Where do disputes come from?
Interestingly, the root of the controversy about this research is not whether the team has done scientific experiments to prove where the droplets will fall, but that the research has caused people to wonder how much droplets can be contagious.
When the virus carrier coughs or sneezes, the virus will fall on the surface of the object with droplets, and when the next person touches, the new coronavirus will spread from person to person.
Research data indicates that the survival time of the virus in vitro depends on the nature of the surface of the object.
But how much virus density is needed to infect the next person has always been the question scientists really want to answer. For example, a crowded indoor space will have more viral load than an open outdoor space.
At the same time, contact time is also important. The risk of saying hello to neighbors on the sidewalk may be less than the risk of drinking coffee with several friends in an outdoor cafe.
The possibility of the virus spreading in the air is also controversial among researchers around the world. Some people think that if the virus spreads in the larger droplets of coughing, sneezing or exhalation, it will quickly fall to the ground.
Others believe that if the virus spreads through a finer "aerosol", it can stay in the air for a longer period of time, thereby bringing a higher risk of infection. Others believe that in any case, there is no clear distinction between these two categories.
As for whether to run outdoors during the outbreak? Many experts say that exercise is still one of the means to improve immunity, but try to avoid crowded spaces as much as possible, or choose online exercise.
On Twitter, some marathon runners saw Blocken's research and agreed to maintain a longer social distance between their companions or riders.
The marathon runner said: "You can say that I will go running with one or two partners I know very well and claim that they are not sick. I believe this is possible, but it is not foolproof."
Faced with uncontrolled disputes, Blocken said in an interview with the media: "Our purpose is to expect more people to realize that they should keep a safe distance. I am not saying that everyone should not go out for running and cycling, instead I give The message is encouragement, that is to keep a distance of more than 1.5 meters for running or cycling. "
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