CDC studies on superspreading events at fitness facilities

Study 1: COVID-19 Outbreak Among Attendees of an Exercise Facility — Chicago, Illinois, August–September 2020 – CDC Morbidity and Mortality Weekly Report

Study 2: Community Transmission of SARS-CoV-2 at Three Fitness Facilities — Hawaii, June–July 2020 – CDC Morbidity and Mortality Weekly Report

Commentaries: Going maskless is a key factor in Covid-19 outbreaks at gyms, studies say – CNN AND A Chicago gym saw dozens of COVID-19 cases after infected people attended HIIT classes without masks – Insider