Overview: Researchers have identified levels of exercise that exponentially increase the release of aerosol particles and explain why exercise intensity may be associated with transmission of infection.
sauce: TUM
Prior to the study, it was known that the respiratory volume of untrained people increased from about 5-15 liters / minute at rest to over 100 liters / minute during exercise. Highly trained athletes actually reach levels of 200 l / min.
It was also known that many people were infected with the SARS-CoV-2 virus while exercising indoors.
However, how exercise intensity is related to the concentration of aerosol particles in exhaled breath and the actual amount of aerosol that an individual exhales per minute, and therefore the potential to spread infections such as SARS-CoV-2. It was unclear how it was associated with the risk.
However, this information is urgently used to design mitigations for school gymnasiums and other indoor sports facilities, fitness studios, or discos, for example, to avoid shutdown in the event of a serious wave of infection. Is required.
The new methodology provides individually measurable aerosol values
A team led by Henning Wackerhage, professor of kinetic biology at Technische Universität München (TUM), and Christian J. Kähler, director of the Institute of Fluid Mechanics and Aerodynamics at Technische Universität München, is new to study these questions. Survey method.
Their experimental equipment first filtered and removed aerosols that were already present in the surrounding air. In subsequent ergometer stress tests, subjects inhaled purified air through a special mask covering their mouth and nose.
Exercise intensity gradually increased from rest to the point of physical fatigue. The mask was connected to a bidirectional valve that allowed only exhaled breath to escape. The amount of aerosol particles released per minute was then measured and directly linked to the current performance of healthy subjects aged 18-40 years.
Moderate aerosol release during moderate exertion
Therefore, researchers were able to investigate for the first time how many aerosol particles an individual exhales per minute at different levels of exercise intensity.
Results: Aerosol release during exercise initially increased moderately, with an average workload of approximately 2 watts per kilogram of body weight. However, beyond that point, it rose exponentially.
This means that a person weighing 75 kilograms will reach that threshold with an ergometer reading of about 150 watts. This corresponds to the modest effort of a casual athlete and probably comparable to the modest jogging exercise intensity.
Aerosol emissions from well-trained athletes were significantly higher than those of untrained subjects with maximum effort due to their much higher minute ventilation. Researchers did not find a significant difference in particle emission by gender.
Protective measures are important for high-intensity training
Aerosol experiments provide only indirect knowledge of the amount of virus in the exhaled breath, but this study manages indoor activity when the wave of infection and low-immune populations can overwhelm the medical system. It suggests a useful starting point for doing so.
“Based on our results, we distinguish between moderate endurance training with a maximum intensity of 2 watts per kilogram of body weight and high intensity to maximum intensity training. Aerosol with a high intensity workload that exceeds the initial benchmark. Special protective measures are needed if the risk of infection with serious consequences is high due to the rapid increase in release, “says research leader Professor Wacker Hage.
“Ideally, that kind of training would be moved outdoors. If that isn’t possible, participants should also do a test to make sure no infected person is in the room. You need to maintain a proper distance and run a highly efficient ventilation system.
“In addition, training at lower intensity and shorter sessions reduces the risk of infection. It may be possible for young, fit athletes to wear masks during training.”
For low workloads such as easy to moderate intense endurance training, Professor Wackerhage requires less protection and can control the risk of infection by distance and ventilation system.
The research team is currently conducting experiments to compare aerosol emissions during intensity and endurance training and correlate them with subject age and physical characteristics.
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author: Henrikebauden
sauce: TUM
contact: Henrikebauden – TUM
image: The image is in the public domain
Independent research: Open access.
“The emission of aerosol particles increases exponentially above moderate exercise intensity, resulting in excessive emission during maximum exercise,” Henning Wackerhageetal. PNAS
Overview
Emissions of aerosol particles increase exponentially above moderate exercise intensity, resulting in excessive emission during maximal exercise.
Severe Acute Respiratory Syndrome Many airborne pathogens, such as coronavirus 2 (SARS-CoV-2), are transmitted indoors via aerosol particles.
During exercise, lung ventilation can increase more than 10-fold, so exercisers exhale more aerosol-containing air. However, it is currently unknown how exercise affects the concentration of aerosol particles in exhaled air and the overall release of aerosol particles.
As a result, we have developed a method for measuring the concentration of aerosol particles in the exhaled breath, lung ventilation, and the release of aerosol particles during a step-by-step exercise test up to rest and fatigue. Using this method, eight women and eight men were tested in a descriptive study.
It was found that the concentration of aerosol particles in exhaled breath increased significantly from 56 ± 53 particles / liter at rest to the maximum intensity of 633 ± 422 particles / liter. Aerosol particle emissions per subject increased 132-fold from 580 ± 489 particles / min at rest to over 76,200 ± 48,000 particles / min at maximum exercise.
Although there was no gender difference in aerosol particle release, endurance training subjects released significantly more aerosol particles during maximal exercise than untrained subjects. Overall, the emission of aerosol particles increased moderately up to about 2 W / kg exercise intensity and then exponentially.
Taken together, these data partially account for super-spreader events, especially during high-intensity group exercise indoors, requiring strong infection control measures, especially during exercise at intensities above ~ 2 W / kg. It may suggest that it is.
It is necessary to investigate the influential factors such as the airway during exercise and the hydration status of the whole body regarding the formation of aerosol particles.
