That’s a good question.
There are a lot of reports that covid-19 also affects the heart. But it’s not totally clear, if the virus (sars-cov-2) directly infects the heart. Or if the exaggerated inflammatory response causes the myocardial injury. The receptor, how sars-cov-2 enters the cells of the lungs (ACE2), is also highly expressed in the heart. So a direct infection could be possible.
Asymptomatic means that there are no symptoms. If you have an asymptomatic course of the disease, you will not know that you have it (only if you get tested). Hard training, through a viral infection, puts you at greater risk for developing myocarditis. But even myocarditis is often asymptomatic. So it’s possible that you have covid-19 and myocarditis and you never know it, or have any symptoms. (too complicated?;-))
What could/should be the conclusion!?
Play it save with training if you are at risk and not sure if you could be infected.
Also be aware of the untypical symptoms of covid-19 – gastrointestinal (diarrhea, stomach pain…), loss of smell/taste, conjunctivitis…
If you get the disease, be very careful with training and do not start too early.
But if you are healthy, don’t worry too much and stay active!