• Research published in JAMA Network Open found that during moderate exercise, participants with symptoms consistent with long COVID experienced reduced exercise capacity, including muscles fatiguing faster and irregular breathing.

• Experts suggest not pushing through it, but rather making a slow return to exercise.

Although it will likely take years or even decades to understand all the nuances with lingering effects of COVID-19, the condition known as “long COVID” has already been linked to persistent fatigue, headache and brain fog. Now, a research review highlights another downside: difficulty getting back to exercise.

Published in JAMA Network Open, the analysis pooled data from nine studies that focused on COVID and its effects on exercise performance.

The meta-analysis included both men and women, and participants ranged in age from 39 to 56. It also included those both hospitalised for COVID and those not. The results from those who’d recovered from the virus without lingering effects was compared to a similar-sized group who had symptoms consistent with long COVID.

They found that during moderate exercise, the group with lingering long COVID symptoms had reduced oxygen extraction in the muscles—which means they fatigued during exercise more quickly—as well as irregular breathing patterns that made exercise more challenging.

Although deconditioning was considered a potential factor, these exercise tests were conducted three to six months after COVID hospitalisation, according to first author Dr Matt Durstenfeld,, cardiologist and clinical researcher. That means with consistent exercise, deconditioning from being in the hospital would be a more minor factor compared to the effects of inactivity in the weeks after recovery. Durstenfeld said even if the participants had been sedentary in general it wouldn’t explain everything they found—as in, someone can be sedentary for months and they should still have better exercise capacity than the study participants were showing.

Also, there were a number of other patterns that negatively affected exercise performance that aren’t related to deconditioning, he told Runner’s World. Most notably, the alterations in muscle oxygen extraction and dysfunctional breathing were likely less about sedentary time during COVID and more about changes in the autonomic system — as if the “fight or flight” response had somehow reset poorly as a result of the virus.

“Since most of the studies included only a single exercise test for each participant, it’s unknown whether this effect is permanent,” said Durstenfeld. “For example, one study that repeated the tests found no improvement, and another found a small improvement, but still a significantly lower exercise capacity compared to controls without COVID.”

He added that one of the studies included individuals who had these fitness limitations more than a year after a COVID hospitalisation, which implies that effects like these can still be sabotaging exercise capacity long after recovery from COVID itself.

The mechanism for why this might happen wasn’t clear, and Durstenfeld said researchers were surprised to find lung and heart limitations to exercise were not common, even though the results might imply that’s the case. Longer-term trials with more participants are needed to determine the root causes for why this might be happening, along with the development of rehabilitation therapies that might be helpful, he added.

The impulse to simply push harder isn’t helpful, he added, since the body is set up to fatigue more quickly. That means, for now, the advice is to take it slow and increase very gradually over a long duration to try and build more exercise capacity.

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