Outdoor Activity: Benefits and Risks to Recreational Runners during the COVID-19 Pandemic

Running has become one of the most popular recreational sports worldwide. It is an easily accessible form of exercise as there are minimal equipment and sport structure requirements. Aerodynamic simulation experiments showed a risk of droplet exposure between runners when two people run in a straight line at a close distance (slipstream). Thus, running activities require a safe physical distance of 10 meters to avoid droplet exposure, which can be a source of transmission of COVID-19 infection. However, running outdoors during the COVID-19 pandemic is still often done in pairs and even in groups without wearing a mask. Open window theory stated that changes in the immune system occur immediately after strenuous physical activity. Many immune system components showed adverse changes after prolonged strenuous activity lasting more than 90 minutes. These changes occurred in several parts of the body, such as the skin, upper respiratory tract, lungs, blood, and muscles. Most of these changes reflected physiological stress and immunosuppression. It is thought that an "open window" of the compromised immune system occurs in the 3-72-hour period after vigorous physical exercise, where viruses and bacteria can gain a foothold, increasing the risk of infection, particularly in the upper respiratory tract. Outdoor physical activity positively affects psychological, physiological, biochemical health parameters, and social relationships. However, this activity requires clear rules so that the obtained benefits can be more significant while simultaneously minimizing the risk of transmission of COVID-19 infection.