We’ve been conditioned to think of Covid-19 as a respiratory disease—but it’s not just about the lungs. Evidence is emerging that the coronavirus can cause heart damage in people who’ve had mild symptoms or none at all, especially if those people exercise while they’re infected. If you've just had Covid—even if you didn't have symptoms—you need to be aware of myocarditis. That’s cardiologist-speak for what happens when the muscular walls of the heart become inflamed, weakening the organ and making it more difficult for it to pump blood. It’s not a newly discovered condition, and it turns up pretty rarely, but when it does, it’s most often triggered by an infection. Strenuous activity while the heart is weakened can cause swelling in the legs, dizziness, shortness of breath, and—in serious cases—irregular heartbeat, cardiac arrest, and sudden death.