Covid-19: new study explains why gyms (and not only) can be transmission hubs

The numbers are impressive, but experts stress that this finding applies to several other locations.

Scientists already knew that the airborne transmission of covid-19 through aerosols – small particles that spread in the air when we breathe – is considerably greater during the practice of physical exercise in closed spaces. However, a study published by a team of researchers from the University of Munich reveals that a person emits 132 times more aerosols per minute while exercising than during a moment of rest, something that experts believe can lead to the creation of poles of energy. disease transmission.

The numbers are impressive. When we are completely immobilized, resting, we expel an average of 580 particles per minute. However, during high-intensity physical exercise, taken to exhaustion, a person can expel up to 76,200 particles per minute.

“This data not only explains SARS-CoV-2 transmissions during group exercise indoors, but could also be used to design more targeted mitigation measures for indoor physical activities, such as physical education classes at school. , dance events during weddings or high-intensity gym classes such as spinning”, reads the study.

Henning Wackerhage, the study’s co-author and professor of exercise biology at the Technical University of Munich, was surprised by the result of the study, which brings new depth to scientific knowledge about the number of particles per liter of air, during high-intensity physical exercise.

“We knew that when we exercise, there is more air coming out of the human body. But we didn’t know, and I didn’t expect it, that when we exercise a lot, there are more particles per liter of air.”

To reach this conclusion, the scientists put several people exercising to exhaustion on stationary bikes with a silicone mask on their face, which was attached to a plastic container, which stores and measures the numbers of particles. This “closed loop” of air allowed the researchers to get a clearer picture of the number of particles expelled by each of these individuals, eliminating external sources of contamination.

However, the team of German researchers admits that the study has some limitations, starting with the number of people who participated in the sample: only 16 people were tested. In addition, none of them were positive for covid-19, but the scientists justify this absence with ethical concerns about the possible health risks of the participants.

The scientists also stress that, although the emission of aerosol particles is one of the main risks for the transmission of SARS-CoV-2, it is not the only risk, as the infection also depends on the concentration of the virus in the released particles.

The study also shows that concentrations of aerosol particles in expired air vary greatly from person to person. People with better physical preparation expel 85% more particles than other participants. The researchers justify with the greater need to supply oxygen to the muscles. According to the results of this study, the distribution of particles does not show a significant variation between men and women.

“It’s not just gyms.” Attention to ventilation

For specialists, it is not news that less ventilated spaces and with a greater concentration of people represent a greater risk of transmission of diseases such as covid-19. Places where there are many people singing or dancing are indicated by health authorities as potential transmission sites. In this sense, isolating gyms as the most favorable places for the spread of the virus is not fair, underlines Bernardo Gomes, a public health doctor.

“It’s not just the gyms, it’s the indoor physical spaces without ventilation. Ventilation is most important. Indoor air quality will have to be a priority for years to come. Places with less ventilation are the most conducive to the need to wear a mask”, stressed the Public Health doctor, who added that people can look for larger establishments, which allow better air circulation and more spacing between people.

In addition, gyms are not all the same and the use of a mask does not solve the problem when we practice some modalities in gyms. Therefore, the specialist advises you to take into account the hours of use and to pay attention to the ventilation of interior spaces where you exercise, particularly at times when the virus is known to be circulating with greater intensity.

It is recalled that the average number of infections increased again in Portugal. This Wednesday, the National Institute of Health Doutor Ricardo Jorge (INSA) revealed that the number of cases rose from 22,805 to 29,101 daily cases in Portugal and all regions have a coronavirus transmissibility index (Rt) above the threshold of 1. .

According to INSA’s weekly report on the evolution of the covid-19 pandemic in the country, the Rt at the national level dropped from 1.23 to 1.13, but all regions present the average of this indicator at five days above 1, the which “indicates an increasing trend” of infections.

The North has an Rt of 1.12, the Center with 1.06, Lisbon and Vale do Tejo with 1.20, the Alentejo with 1.09, the Algarve with 1.12, the Azores with 1.21 and the Madeira with 1.18, according to the report. The value of the Rt – which estimates the number of secondary cases of infection resulting from each person carrying the virus – has been greater than 1 since April 26.