Characterization of Aerosol Generation During Various Intensities of Exercise

Abstract

Background Characterization of aerosol generation during exercise can inform the development of safety recommendations in the face of COVID-19. Research Question Does exercise at various intensities produce aerosols in significant quantities? Study Design and Methods In this experimental study, subjects were eight healthy volunteers (six men, two women) who were 20 to 63 years old. The 20-minute test protocol of 5 minutes rest, four 3-minute stages of exercise at 25%, 50%, 75%, and 100% of age-predicted heart rate reserve, and 3 minutes active recovery was performed in a clean, controlled environment. Aerosols were measured by four particle counters that were place to surround the subject. Results Age averaged 41 ± 14 years. Peak heart rate was 173 ± 17 beat/min (97% predicted); peak maximal oxygen uptake was 33.9 ± 7.5 mL/kg/min; and peak respiratory exchange ratio was 1.22 ± 0.10. Maximal ventilation averaged 120 ± 23 L/min, while cumulative ventilation reached 990 ± 192 L. Concentrations increased exponentially from start to 20 minutes (geometric mean ± geometric SD particles/liter): Fluke >0.3 μm = 66 ± 1.8 → 1605 ± 3.8; 0.3-1.0 μm = 35 ± 2.2 → 1095 ± 4.6; Fluke 1.0-5.0 μm = 21 ± 2.0 → 358 ± 2.3; P-Trak anterior = 637 ± 2.3 → 5148 ± 3.0; P-Trak side = 708 ± 2.7 → 6844 ± 2.7; P-Track back = 519 ± 3.1 → 5853 ± 2.8. All increases were significant at a probability value of <.05. Exercise at or above 50% of predicted heart rate reserve showed statistically significant increases in aerosol concentration. Interpretation Our data suggest exercise testing is an aerosol-generating procedure and, by extension, other activities that involve exercise intensities at or above 50% of predicted heart rate reserve. Results can guide recommendations for safety of exercise testing and other indoor exercise activities.

Aerosol particle emission increases exponentially above moderate exercise intensity resulting in superemission during maximal exercise

“…To be able to do this, we needed to developed an experimental set up that detects the concentration of particles in a partial flow of exhaled air without correction ( 24 – 26 ) that reduces the errors that can be caused by uncontrolled inflow of particle-free air ( 13 , 14 , 27 , 28 ). By measuring aerosol particle concentration and ventilation in one individual, we were able to calculate aerosol particle emission that is a more direct measure of the risk of pathogen transmission by aerosol particles by one individual than the aerosol particle concentration in exhaled air or in room air ( 16 – 19 , 25 ).…”

“…These individuals have been termed “superemitters” ( 13 ). The number of aerosol particles emitted by a person per unit of time varies and increases when that person talks, coughs, sings ( 14 , 15 ), or is physically active ( 16 – 20 ). It has also been shown that the number of emitted aerosol particles is influenced by the airway hydration status ( 20 , 21 ).…”

“…Current research on airborne pathogen transmission is limited by the fact that most studies only report the concentration of aerosol particles in expired air ( 13 , 14 , 18 , 20 , 24 – 26 ) or in a room ( 16 – 19 , 23 ) but not the emission of aerosol particles by one individual. Since the latter is required for assessing the risk of infection, we developed a method to measure both the concentration and emission of aerosol particles from rest up to maximal exercise.…”

Monitoring SARS-CoV-2 in air and on surfaces and estimating infection risk in buildings and buses on a university campus

“…Aerosol concentrations generated from wind instruments, such as trumpet, oboe, or bass trombones tends to be higher than those generated by normal speaking [ 11 ]. In a gym, the sustained heavy breathing during intensive aerobic exercise generates proportionately (to heart rate) higher concentrations of aerosols [ 12 ], and mask fit is often intentionally compromised when people have trouble breathing to allow for more air exchange, which can further diminish the effectiveness of face masks in obstructing respiratory jets [ 13 ]. Use of shared exercise equipment and public drinking fountains may also spread the virus through surface touch points, given high virus stability on non-porous surface [ 7 ].…”

New Insights into the Prevention of Hospital-Acquired Pneumonia/Ventilator-Associated Pneumonia Caused by Viruses

“…58 Talking, shouting, exercise, labored breathing, singing, and coughing all increase aerosol production. [59][60][61] The estimated filtration efficiency of most surgical masks ranges from 40 to 60%. 57,62 In practice, this means that surgical masks decrease the risk of transmission between healthcare workers and patients but do not eliminate it.…”