COVID-19 has led many people to rediscover the joys of walking, jogging and bicycling as so many Americans are encouraged to limit travel and to socially isolate. The pandemic has even caused a surge in bike sales across the United States, according to Reuters.
Exercise is good for the body; it’s a way to stay healthy and also a way to relieve stress during these tense times. And one recent study even suggests exercise might help prevent people from contracting COVID-19. There is just one thing wrong with this equation – the math around social distancing and outdoor exercise.
To limit the spread of COVID-19, it has been recommended that people stay 6 feet apart, a distance universally seen as safe enough to prevent virus aerosols, or droplets, from spreading from one person to another. But “that only applies when people are standing still,” said AccuWeather Founder and CEO Dr. Joel N. Myers.
What is a safe distance to maintain when people are walking, running or biking outside?
If a person is riding a bike at 15 miles per hour, that’s equivalent to moving 22 feet per second. If someone is walking at a brisk 4-mph pace, that’s equal to going 6 feet per second.
“As the droplets come out of a person’s mouth that are in the air, if you’re moving quickly toward where those droplets are, you need to create a much greater distance,” said Myers. “And if you’re both moving in the same direction at those speeds, you probably should be at least 20 or 25 feet apart. And if you’re biking, you probably need to be more like 30 to 40 feet apart.”
Wind and air currents also have to be factored into creating a safe distance between people in motion. Larger aerosols fall to the ground faster than smaller droplets, which stay in the air longer.
“Small droplets, because of turbulence – up and down air currents – may stay in the air for several minutes before gravity finally pulls them down,” Myers said.
A new study found that runners and walkers may create a wake of air behind them that could carry the droplets for 15 feet or more, according to the New York Times. The results of the study’s tests indicated that the largest exposure for a runner trailing another runner exists when the trailing person is in line behind the leading person, essentially running in the leader’s slipstream.
The “exposure increases as the distance between the leading and trailing person decreases,” the study found.
The study recommends that to avoid substantial droplet exposure, runners should either avoid another runner’s slipstream or keep a larger social distance, where the distance increases with the walking or running speed.
“The 6-foot guidelines really only apply to stationary people and don’t take into account if two people are moving in the same direction because the person behind is moving quickly into the trail of breath from the person in front,” Myers said. “Six feet is not the magical answer in all situations.”