Medical experts are working hard to figure out what causes long COVID, a condition in which symptoms last for months after a COVID-19 infection, on top of dealing with new symptoms.
Brain fog, fatigue, and headaches have all been mentioned as long COVID symptoms.
Reduced exercise capacity has now been revealed as another long-lasting consequence of SARS-CoV-2, months after infection.
Researchers from UC San Francisco and Zuckerberg San Francisco General Hospital found 38 prior studies that tracked the exercise performances of more than 2,000 participants who had previously had COVID-19, including those with likely long COVID, in their study published in JAMA Network today.
The researchers focused their study on nine trials, comparing the exercise capacities of 464 persons with symptoms suggestive of long COVID versus those of 359 participants who had recovered from the virus.
The participants’ average ages in these nine trials ranged from 39 to 56, and their average BMIs varied from 26 (overweight) to 30 (obese).
The results show that the long COVID population in this subgroup may have lower oxygen extraction in the muscles, abnormal breathing patterns, and a reduced capacity to increase heart rate during exercise to meet cardiac output.
The researchers also found indications of deconditioning, which they said happens to some level after the majority of physical disorders that cause immobility. It’s significant to note that not all of the results were consistent with deconditioning.
At least three months after SARS-CoV-2 infection, participants underwent cardiopulmonary exercise testing (CPET), in which oxygen and carbon dioxide levels, along with other indicators of heart and lung function, were assessed while they used a treadmill or stationary cycle.
Long COVID patients may find doubles tennis and lap swimming very strenuous
When comparing how well people could exercise, researchers found that the peak rate of oxygen in the long COVID group was 4.9 ml/kg/min lower than in the recovered group.
First author Matthew S. Durstenfeld, MD, MAS, of the UCSF Department of Medicine and the Division of Cardiology at Zuckerberg San Francisco General Hospital, says that this difference is equal to 1.4 metabolic equivalent of tasks (METs), a measure of how much energy is used during physical activities.
He added that the loss in oxygen peak rate would be equivalent to a woman’s exercise capacity of 9.5 METs at age 40 decreasing to 8.1 METs at age 50.
Durstenfeld said that another way to look at it is that someone who plays doubles tennis might need to switch to golf with a cart or stretching exercises, while someone who swims laps might find that low-impact aerobics is a better fit.
“But it’s important to note that this is an average,” he said. “Some individuals experience a profound decrease in energy capacity and many others experience no decrease.”
In their review of the studies, the researchers noted that while there was “a low confidence in the magnitude of effect,” there was “modest but consistent” evidence that exercise ability is decreased in persons with long COVID.
They said this was because of a lack of consistency in study definitions of long COVID and CPET modalities, as well as oversampling of hospitalized participants and those with acute symptoms referred to long COVID clinics and for CPETs.
Pre-infection CPETs were not conducted in any of the investigations.
“Further research should include long-term observational assessments to understand the trajectory of exercise capacity,” added senior author Priscilla Y. Hsue.
“Trials of potential therapies are urgently needed, including studies of rehabilitation to address deconditioning, as well as further investigation into dysfunctional breathing, damage to the nerves that control automatic body functions and the inability to increase the heart rate adequately during exercise.”
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