And experts have some theories as to why.
By Melinda Wenner Moyer
When Natalie Hollabaugh tested positive for Covid-19 in March 2020, her recovery felt extremely slow. Eighteen months later, she was still suffering from a litany of symptoms, including fatigue, shortness of breath, headaches and joint pain. She saw a cardiologist and a pulmonologist, who both ruled out other health problems, she said. And they advised her to start exercising, suggesting that some of her symptoms may have been a result of being out of shape. So Ms. Hollabaugh dutifully began using an exercise bike, speed walking on a treadmill and walking her dogs several miles a day.
But instead of helping, her new exercise regimen only exacerbated her symptoms. “I had never felt worse,” said Ms. Hollabaugh, 31, a lawyer who lives in Portland, Ore. She found she had to start taking daily naps, that her heart rate would skyrocket even when she was at rest and that she was so tired she couldn’t concentrate.
As one of the many Americans suffering from long Covid, a condition characterized by new or lingering symptoms that can be felt for months after a coronavirus infection, Ms. Hollabaugh is not alone in experiencing setbacks with exercise. Natalie Lambert, a biostatistician and health data scientist at the Indiana University School of Medicine, has collected self-reported data from more than a million long Covid patients through a collaboration with Survivor Corps, a Facebook support group for Covid survivors. Patients frequently report that their doctors have advised them to exercise, she said — but many say that when they do, they feel worse afterward.
“The research that I’ve done has shown that inability to exercise is one of the most common long-term symptoms,” Dr. Lambert said. Some people are simply too tired to exercise, she said, while others experience debilitating symptom relapses like increases in fatigue, brain fog or muscle pain. This worsening of symptoms after engaging in even just a little bit of physical activity — what is sometimes called “post-exertional malaise” — seems to be common among long Covid patients. When researchers performed an online survey of 3,762 people with long Covid, as part of a study published in August, they found that 89 percent reported post-exertional malaise.
These exercise-induced problems are not, however, merely the byproduct of becoming out of shape. The effects “are very, very different from normal and simple detraining,” said Dr. David Systrom, a pulmonary and critical care physician at Brigham and Women’s Hospital in Boston. They also don’t seem to be the result of lung or heart injury.
In one small study published in January, for example, Dr. Systrom and his colleagues compared 10 long Covid patients who had trouble exercising with 10 people who had never tested positive for Covid-19, but who had unexplained shortness of breath after exercise. The researchers found that nobody in the study had abnormal chest CT scans, anemia or problems with lung or heart function, suggesting that organ injury wasn’t to blame for their symptoms. Yet when the long Covid patients exercised on a stationary bicycle, Dr. Systrom found that some veins and arteries were not working properly, preventing oxygen from being delivered efficiently to their muscles.
Nobody knows why these blood vessel problems occur, Dr. Systrom said, but another one of his recent studies suggested that long Covid patients experience damage to a certain kind of nerve fiber involved in how organs and blood vessel function.
Other research on exercise intolerance implicates problems with how the heart rate responds to exercise. In one study published in November, researchers from Indiana studied 29 women who had tested positive for Covid-19 about three months earlier. When these women underwent a six-minute-long walking test, their heart rates didn’t accelerate as much — or recover as quickly — as the heart rates of 16 similar women who had not been infected with Covid-19.
“Clearly, there’s something going on that’s interfering with that normal response,” said Stephen J. Carter, an author of the study and an exercise physiologist at the Indiana University Bloomington School of Public Health.
Dr. Lambert pointed out that some patients with long Covid are also diagnosed with postural orthostatic tachycardia syndrome (or POTS), a disorder that affects blood flow. In people who have POTS, “the nervous system can’t regulate the things that it’s supposed to automatically control, like heart rate, blood pressure, sweating and body temperature,” she said. Yet “those are all things that when you’re exercising need to be regulated properly.”
Some doctors also point to parallels between patients with long Covid and those with chronic fatigue syndrome, who have severe fatigue, memory and cognitive problems, and often muscle or joint pain. For decades, physicians advised chronic fatigue patients that exercise would improve their symptoms, but for many patients, exercise actually made their symptoms worse and now is no longer recommended.
In 2021, Dr. Systrom and his team studied 160 chronic fatigue patients, and found that when they exercised, they experienced many of the same blood vessel problems observed in long Covid patients, while control subjects did not. “We’re essentially finding the exact same thing” when it comes to potential mechanisms, he said.
This all leads to one question: Should Covid patients who are having trouble with exercise continue to ramp up their physical activity? Nobody knows — and opinions differ. “There are both patients and doctors who are vehemently against any exercise” because of these issues, Dr. Systrom said. But he also said that exercise can be possible, and even beneficial, after long Covid patients receive proper treatment. “If you can get the patient in a better place with medications, then you can embark on a graded exercise program without precipitating crashes,” he said.
Dr. Lambert agreed. “You can’t just jump into exercise, or you’re going to be set back,” she said, but you should “slowly try to reincorporate it if you are feeling better.” She added that long Covid can manifest in different ways, so doctors and patients may need to tailor their recommendations to patients’ needs.
“That’s really the story of Covid — that for every patient, long Covid is different,” she said. “There’s probably never going to be a one-size-fits-all recommendation for exercise.”