Huffing and puffing by the numbers: Why gyms are so infectious

Gyms were thought to be dangerous because of viral particles being left on equipment. Not the main problem.

Gyms were thought to be dangerous because of viral particles being left on equipment. Not the main problem. Photo: Getty

In the confusion of the pandemic’s first year – as people wondered where was safe and where was not – gyms were quickly identified as the ideal super-spreader venue.

Even when gym owners were scrupulous about following public health advice on how to keep their patrons safe, people still got infected.

In October last year, a Sydney gym that had reportedly been praised and thanked by the NSW Health Department for taking “extra precautionary measures” against the coronavirus was caught out.

On one day, 15 confirmed cases linked to the gym were reported to the department.

Billy Kokkinis, executive director of City Gym, was in “complete shock”.

He told the Daily Telegraph: “You can’t tell me one day that we’re the cleanest gym and then the next day tell me we’re a hotspot.”

No doubt, machines were being diligently wiped down and sprayed with disinfectant, social distancing was observed, masks worn in fitness classes and windows kept open.

No escaping a shower of viral germs

The extent to which some of these precautions were useful in a gym setting have come into doubt.

It was assumed that the biggest problem was poor ventilation and high respiration rates. In other words, lots of viral germs and no where else to go but on the guy in the neighbouring treadmill or cycle.

The question was: How many aerosol viral particles are being huffed and puffed into the air during a workout?

Not an easy question to reliably answer.

But according to a study published this week, German fluid dynamics researchers have apparently solved the mystery.

How did they do it?

Eight men and eight women, aged 18 to 40, each took their turn on a stationary bicycle inside an airtight tent.

The participants wore silicone masks that caught their exhalations and sent them through tubes to a machine where every particle was counted.

At first, the cyclists sat on the bike, where they produced about 500 aerosol particles per minute.

They then began cycling, and the mist thickened as they picked up the pace. They ended up going flat out until they were spent.

During that time, the amount of particles breathed out increased by  132-fold, producing more than, on average, 76,000 particles per minute, on average, at the peak of exertion.

The researchers were expecting an increase in expelled particles, but  were “surprised” by the extent of what, in infected people, would be a viral germ shower.

With a room full of spin cyclists or treadmill sprinters, is there a potential bath of infection to be reckoned with?

The solution: More open windows, fans, air filters, stricter social distancing and mask-wearing.

And hoping for the best.

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