WHO has updated its guidance on the use of masks ( https://www.who.int/es/emergencies/diseases/novel-coronavirus-2019/advice-for-public/when-and-how-to-use-masks ) and among the tips for use during physical activity advises that masks should not be worn during intense exercise, as they restrict the flow of breath and could be dangerous for athletes.
For this reason, it advises that interpersonal safety measures be respected, as well as ensuring proper ventilation of the space where exercise is being performed.
On the other hand, the WHO places special emphasis on keeping areas of common use and intensive contact clean and sterilized, the latter being especially indicated for gyms and closed sports facilities.