Strenuous exercise causes over 100 times more aerosols to be exhaled out compared to those who are resting with higher risk of spread of infections, suggests a study published in the Proceedings of the National Academy of Sciences.1

Researchers from Germany measured pulmonary ventilation, concentration of aerosols in exhaled air and aerosol particle emission at rest and during exercise on a stationary bike in a clean room. Sixteen participants were selected for the study. None of them had Covid-19. Filtered clean air was breathed in through a silicone face mask. Only the exhaled air entered the outflow through a two-way valve connected to the face mask.

The concentration of aerosol particles in exhaled air rose from 56  particles per liter at rest to 633 particles per liter at maximal intensity of exercise. The emission of aerosol particles also increased from 580 particles per minute at rest to 76,200 particles per minute “super emission” at maximal intensity of exercise. People who engaged in endurance activities exhaled out aerosols in a significantly more proportion.

This study has quantified the aerosol particles at rest and also during maximal intensity exercise. Gyms and fitness centers, where high-intensity group exercises are a regular feature, therefore can be potential superspreaders. Hence, robust measures to prevent infection are a must to prevent spread of respiratory viral infections. Besides complying with covid-appropriate behavior, improving ventilation, air filtration in gyms and indoor spaces where group exercises are held, are key to reducing the spread of aerosols. The authors also recommend “15-min airing breaks in between classes, pre-exercise infection testing of participants, safety shields in between exercisers, mobile air filters, and the wearing of masks even during exercise”.

Reference

1. Mutsch B, et al. Aerosol particle emission increases exponentially above moderate exercise intensity resulting in superemission during maximal exercise. Proc Natl Acad Sci U S A. 2022 May 31;119(22):e2202521119. doi: 10.1073/pnas.2202521119.