In rare cases, the virus can directly infect and inflame your ticker. That’s the “myocarditis” you probably heard folks talk about at the beginning of the pandemic. (But this is super rare, especially in athletes; even in the earlier days of the pandemic, researchers estimated the rate of COVID-related myocarditis to be around 1%, according to a 2022 review and meta-analysis.)
But even if we’re not talking actual damage, the infection can still affect your heart.
“The other concern is there can sometimes be just some irritability of the heart after COVID,” Dr. Erlandson says. “[You] may be more likely to have irregular heart rate or more likely to have a rapid heart rate response with exercise when you’re still kind of sick or not feeling well.” And that can play a role in your performance by increasing fatigue and decreasing endurance—and having everything just flat-out feel harder.
We still don’t know how bad the combo of exertion and acute COVID might be for your cardiovascular system, says Dr. Erlandson. Like we said, there’s just not a lot of data to draw from. However, “we are concerned about potential damage to the heart or putting someone at risk of going into a dangerous heart rhythm or causing more pain and causing symptoms to last longer,” she says.
3. You might stress your system at the very time it needs rest.
Both COVID and exercise—especially the intense kind—separately can increase inflammation. This double whammy could, in theory, make recovery from the virus more difficult, Hector Bonilla, MD, a clinical associate professor of medicine-infectious disease at Stanford University and co-director of Stanford’s Post-Acute COVID-19 Syndrome Clinic, tells SELF.
There’s not enough scientific evidence to say for sure whether exercising intensely with COVID can make you feel worse, slow your recovery, or increase your risk of long COVID, which is defined by symptoms that persist for at least three months. But one 2023 review in Frontiers in Physiology does suggest that even mild to moderate exercise during the acute stages of COVID could “aggravate the inflammatory response and further worsen the COVID-19 symptoms.” And based on Dr. Bonilla’s experience treating patients, his advice is “don’t add additional stress to your body.”
While generally healthy people have a lower risk of long COVID, Dr. Bonilla says it’s plausible stressing your system with hard exercise, like a marathon, ultramarathon, or century bike ride, could contribute to long COVID. He has seen some athletes get COVID, recover, and then develop long COVID symptoms a few weeks later when they start working out again.
With all the unknowns still out there with COVID, it’s safer to pull back when you’re sick.
There’s just not a lot of solid research out there showing that exercising with COVID is safe—let alone pushing at your max, 100%, win-me-a-medal-please effort.
“I think anytime we’re sick, we have to just give pause,” Dr. Abeles says. This holds even more true if you have a fever. That should be considered a flat-out dealbreaker, she says.