Should You Exercise Outside During the COVID-19 Epidemic?

As of April 5, 42 US states and the District of Columbia had issued stay-at-home orders, affecting about 90 percent of the population, some 300 million people, in an effort to contain the continuing epidemic of COVID-19, a respiratory illness caused by the SARS-CoV-2 virus.

The long-distance hiking community has seen major trail advocacy organizations, including the Appalachian Trail Conservancy, Pacific Crest Trail Association, Continental Divide Trail Coalition, and others, strongly advising would-be hikers to stay away and urging those on trail to get off as soon as practicable.

Meanwhile, in a recent reversal, the Centers for Disease Control and Prevention is now advising Americans to wear cloth face coverings in public settings where other social distancing measures are difficult to maintain (e.g., grocery stores and pharmacies), especially in areas of significant community-based transmission.

So, thru-hiking is out. But is it OK to go outside to run, ride a bike, or hike? Recent headlines have generated confusion as to what is currently allowed or recommended. Here is a look at the latest research and expert advice to clear up some of the confusion.

Transmission

According to the CDC, SARS-CoV-2 is highly contagious and spreads by two primary means of transmission: person-to-person and from contaminated surfaces, also known as fomite transmission.

Person-to-Person

This typically occurs when coming in close contact with an infected person. Droplets can be dispersed when a person sneezes, coughs, or even talks, and land in the nose or mouth of a non-infected person. One study found that infected people may be able to transmit the disease for several days prior to showing any symptoms and more than 23 percent of infections may be occurring that way.

Recent studies have heightened concerns about the transmissibility of the virus, including:

• A paper published March 26 in the Journal of the American Medical Association found that “turbulent emissions”—a cough, sneeze, or forceful exhalation—can create “a cloud that can span approximately 23 to 27 feet —well beyond the six feet recommended for social distancing.
• And on March 17, the New England Journal of Medicine published a report on research that found SARS-CoV-2 can remain “viable in aerosols” for up to three hours in experimental conditions.

Headlines about those and other findings have led many people to conclude that nowhere is safe, including the outdoors. But a closer read, and the advice of countless experts, suggest that is not the case.

Regarding the sometimes-arcane debate about the meaning of “airborne” transmission: Technically, the virus that causes COVID-19 is not “airborne,” but it still can be transmitted through the air via respiratory droplets. The difference has to do with the size of the droplets. Generally, droplets of less than 5 micrometers are deemed “airborne” because they are light enough that gravity doesn’t swiftly pull them earthward. SARS-CoV-2 is carried in droplets larger than that, which cannot stay suspended for long.

The findings about persistence in the air and distance of travel by the virus were both based on experimental conditions. The aerosol viability study, for example, used a nebulizer, a device to turn liquid into aerosols, and a “Goldberg drum … an aluminum drum (70 L) with a series of internal baffles.” That’s the size of a pretty roomy backpack.

But experts stress that being outside is worlds apart from such experimental conditions. Natural ventilation, particularly if someone is moving, disperses droplets rapidly. A lower “viral load”—the density of viral particles—reduces the chance of infection. The public-health rule of thumb for “significant exposure” is 15 minutes of face-to-face interaction or two hours in the same room with a person.

Asked if it’s possible to catch COVID-19 from a passing jogger (and vice versa), Dr. Charles Gilks, an international public health specialist at the University of Queensland in Australia, said, “I can’t say there are no risks, but I think they’re very, very, very small.”

“If you’re going out and you’re hiking or biking or running and you’re not within, say, six feet or 10 feet of another person, I would consider that a healthy, safe practice,” epidemiologist Albert Ko of Yale University told National Public Radio.

Bottom line: When it comes to COVID-19, hiking, walking, running, and biking outside poses little or no risk, provided you aren’t exercising in large groups and are keeping your distance when passing people.

Contaminated Surfaces

Researchers have found that SARS-CoV-2 can persist on surfaces for varying lengths of time in laboratory conditions:

• Up to 72 hours on plastic and stainless steel.
• Up to 4 hours on copper.
• Up to 8 hours on cardboard.

Sunlight does not kill the coronavirus, but things like ventilation and precipitation in an outdoor environment tend to disperse viral particles and make them less likely to persist. According to the CDC, “Generally, coronaviruses survive for shorter periods at higher temperatures and higher humidity than in cooler or dryer environments” but there is not “direct data for a temperature-based cutoff for inactivation at this point.”

Bottom line: Although not considered a significant risk, contaminated surfaces are theoretically a concern while recreating outside, such as when opening a gate. Hikers, runners, and bikers should bring hand sanitizer and something to cover their fingers and hands (tissue, plastic bag) when touching surfaces.

To Mask or Not

If you do go outside to hike, bike, or run, should you wear a mask?

Recommendations released April 6 by the Pennsylvania Recreation and Park Society and Get Outdoors PA advise people to “Be considerate. Wear a mask to protect others, as recommended by state and federal authorities.”

However, given ventilation, reduced viral load, and other factors, most experts say there is little likelihood of contracting or transmitting COVID-19 while recreating and wearing a mask isn’t likely to make much difference.

More effective masks, such as surgical masks or N95 respirator masks, properly fitted, would be virtually impossible to wear if you are breathing hard. Cloth masks made from a bandanna or other material and painter’s masks are, at best, a poor or partial barrier to viral droplets, experts say.

Because you are likely to pass people quickly on the trail or bike path, experts say you are unlikely to inhale enough virus to make you sick. So, rather than wear a mask, the smartest thing you can do is keep a safe distance from other people on the trail.

Wearing a barrier that is wet or damp—hard to avoid when breathing hard—is specifically not recommended.

“Once a mask gets wet, maybe from our exhalation, it really begins to decrement in effectiveness in filtering any sort of respiratory particulate matter. So that’s one thing, it would need to be changed,” says Gregory Poland, infectious diseases and vaccine specialist at the Mayo Clinic.

Poland also notes that “you do yourself no favor if you wear a mask and then touch the mask, either to adjust it or take it off in the wrong way.”

Bottom line: Given the markedly reduced viral load in the air outdoors, if you keep clear of people you meet, there is little utility in wearing a mask. However, as a courtesy to others who may have concerns, you can bring a mask and don it when approaching or passing other users.

Getting Out Is Good

It’s worth noting that to date, every US jurisdiction that has issued a stay-at-home order has included an exemption for outdoor exercise and the CDC has made “exercise regularly” part of its recommendations for coping with the stress of the COVID-19 outbreak.

Also, studies show that regular moderate-to-vigorous exercise enhances the immune system, reduces inflammation, and improves overall metabolic health.

“Exercise-induced immune changes reduce risk for common chronic diseases,” according to a 2019 study in the Journal of Sport and Health Science.

On the flip side, people who don’t exercise are much more likely to have co-morbidities that increase their risk of severe illness or death should they contract COVID-19.

With the possibility that shelter-in-place orders will remain in place for weeks or months in some places, getting outside to exercise is actually a pretty good idea.

“If people are practicing sound respiratory hygiene, sound hand hygiene, they’re distancing themselves physically from others outside, and you’re exercising and walking in the park—I think that’s actually a good public health practice,” epidemiologist Ko told NPR.

Be Mindful of Community Resources

Some local and state governments have closed parks and trails stems out of concern — backed up by pre-closing experience — that a sudden wealth of free time will cause more people to decide to hike, bike or go to the beach than usual, making it harder for them to maintain social distancing practices.

If you do go out, don’t let down your guard.

“That’s what we should be striving for, keeping big distances,” Matt Ferrari, Ph.D., associate professor of biology in the Eberly College of Science, and a researcher with the Center for Infectious Disease Dynamics at Penn State, told Runner’s world.

In addition, you don’t want to get into a situation where you need to be rescued, whether for a broken leg, hypothermia (as one PCT hiker was, recently) or COVID-19. When a person is lost, injured or missing in any wilderness setting and a call comes in to 911, a volunteer search-and-rescue group is most likely to respond, says Henrik B. Pedersen, a volunteer with the Santa Fe (New Mexico) Search & Rescue Group.

“These volunteers are aware of the added danger given the COVID-19 pandemic, but have limited protective equipment, and there is no way to rescue an injured person while maintaining social distancing,” he says. If you do go outside, Pedersen says, “be extra cautious and pre-think all outdoor activities relative to dangers and potential injuries so (that) volunteers do not have to expose themselves to this virus.”

Featured image courtesy Ian Roderer, via Maggie Slepian