Transmission of respiratory diseases in high-metabolic environments: A case study of gym

Outbreaks of respiratory infectious diseases have often been reported in fitness centers, likely attributed to high population density, extensive shared surfaces, and elevated metabolic equivalent (MET) levels. This study analyzed the behaviors of 30 gym attendees to establish a connection between exercise intensity and virus exposure. Close interactions among participants were tracked using self-developed wearable devices that utilized computer vision technologies, while surface-contact behaviors were recorded using video cameras. A multi-route transmission model for respiratory infectious diseases was subsequently created, integrating the observed behaviors. The Omicron variant of COVID-19 served as a case study to evaluate infection risk via various transmission routes and to assess the efficacy of interventions. The METs during physical activity were about 3.5 times higher than those recorded at rest. The average interpersonal distance during close interactions in the gym was measured at 0.82 m, with 36.7 % of interactions occurring face-to-face. On average, the participants made contact with surfaces 770.3 times per hour, with 517.5 of these contacts involving public surfaces. The hourly infection rate was calculated at 18.5 %, with long-range airborne transmission and close contact accounting for 70.1 % and 28.5 % of the cases, respectively. To mitigate transmission risk, several intervention scenarios were modeled. These included (1) 100 % mask-wearing with N95 masks and occupancy reduced to 62 % (25 $m^2$/person); (2) 100 % mask-wearing with surgical masks and occupancy reduced to 26 % (59.6 $m^2$/person); (3) no mask-wearing, with occupancy reduced to 18 % (86.1 $m^2$/person). All scenarios fulfilled the criteria for achieving an $R_t$ below 1, indicating that under these conditions, gyms could be reopened safely.