Photo by John Taggart for The New York Times. This is a great article about wearing a mask while working out. https://www.google.com/amp/s/www.nytimes.com/2020/06/17/well/move/exercising-while-wearing-a-mask.amp.html

Update: The World Health Organization released guidance on June 16, 2020, that people shouldn't wear face masks while exercising because it could reduce the ability to breathe comfortably, noting that the most important factor in preventing disease spread is distancing yourself from others. Still, it's everyone's own choice to decide if they want to wear a mask while exercising per https://www.google.com/amp/s/www.cnet.com/google-amp/news/how-to-exercise-with-a-face-mask/

How to adapt your workout while wearing a mask by Colleen Reynolds at osfhealthcare.org. begin at a lower level than what you’re used to and then increase exertion. As you continue, always keep an eye on your heart rate.
Individuals with pre-existing respiratory or cardiovascular conditions should make sure to monitor their heart rate while exercising with a mask.