Crowded exercise spots could feed virus as slipstreams, and people without masks, increase risk

Joggers and cyclists have come out in swarms to make use of public places like the Sea Point Promenade in Cape Town, Delta Park in Johannesburg and the Durban beachfront.

With exercise limited to a three-hour gap from 6am to 9am, crowding in such exercise hot spots has ensued.

But it has been posed that the conventional 1.5m-2m physical distancing gap between people is possibly not enough when walking, jogging or riding - thanks to the slipstream of the person in front.

In other words, standing still and apart at that distance is very different from trailing someone who is moving rapidly and pushing the air they’re exhaling backwards.

Bert Blocken from the Eindhoven University of Technology said in an admittedly not-peer-reviewed paper that “research has shown that the spread of this type of viruses can occur effectively by means of saliva, often in the form of micro-droplets”.

That is why, he posed, “countries worldwide have declared – sometimes by law – a ‘social distance’ of about 1.5m to be kept between individuals”.

The idea is that the droplets will fall and evaporate before they can travel 1.5m.

But, says Blocken: “This social distance has been defined for persons who are standing still. It does not take into account the potential aerodynamic effects introduced by personal movement, such as walking fast, running and cycling.”

Using simulations of airflow around someone exercising at a fast pace, Blocken and the team concluded that people running, cycling or fast-walking behind each other is even more dangerous than doing so side by side as they’re “positioned in the slipstream”.

The paper has not yet been reviewed, and the study was criticised by Vice, which said that the “specifics” and “limitations” of the research were not yet clear, and that though it may prove to be “accurate and useful we have no way of knowing that at the moment”.

The publication also raised questions about whether Blocken should have spoken to the media before the study was published in an official journal.

But Blocken defended the study by saying: “Covid-19 will not wait months or until our paper is published” and emphasised that he was in no way discouraging exercise.

“I have never and nowhere discouraged people from walking, running, or cycling.”

In other words, the public should take heed now instead of waiting until the study is published.

Another exercise tension has been the wearing of masks.

Cape Town resident Allan Rhodes was one of many who took to social media to complain on his neighbourhood Facebook group that joggers were not doing their bit.

“Unbelievable levels of selfishness, idiocracy, on display ... You are not wearing a mask to protect you, you are wearing a mask to protect others. You could be an asymptomatic carrier spreading your aerosols and droplets freely in the streets for an elderly person to breathe in. I am so furious! Do better!”

The Centers for Disease Control and Prevention in the US says it is imperative to wear a mask when out in public, and this includes exercise.

“A cloth face covering should be worn whenever people are in a community setting, especially in situations where you may be near people,” according to the organisation. “Cloth face coverings are especially important to wear in public in areas of widespread Covid-19 illness.”

This is “not a substitute for social distancing” and both should be practised, as should handwashing. 

According to the World Health Organisation, if you go to a public space to walk, run or cycle, it is important, in addition to physical distancing and masks, to “wash your hands with water and soap, before you leave, when you get to where you’re going, and as soon as you get home”.

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