Long Covid is already known to take a toll on health and employment. Now research suggests it can also erase the benefits of years of aerobic exercise.
The research, published on the open-sourced JAMA Network, put together the findings of 38 previous studies tracking the exercise of more than 2,000 participants. It found that those with long Covid face “exertional intolerance” and find it more of a struggle to work out than those who had Covid but recovered.
Becoming out of condition was a common factor that contributed to reduced exercise capacity, but it was not the only one.
Dysfunctional breathing, chronotropic incompetence (inability to increase the heart rate), endothelial dysfunction — which tends to affect more women than men and causes chronic chest pain — and muscular or mitochondrial pathology were also factors that led to exertional intolerance, the study found.
First author Matthew Durstenfeld said exercise intolerance had not been considered a symptom of long Covid because researchers thought it was due to patients becoming out of condition, and that they would regain stamina after recovering from Covid.
The tests were performed at least three months after a Covid-19 infection and involved cardiopulmonary exercise testing (CPET), the principle standard for measuring exercise capacity and diagnosing exercise limitations. Participants also exercised on a stationary bike or treadmill.
More than three months after initial infection, the average participant's peak oxygen consumption (VO2 max) decreased by 4.9 millimetres per kilogram per minute. A person's Vo2 max indicates how much oxygen a their body can use during exercise.
That number is equal to 1.4 metabolic equivalent of tasks (METs), a measure of how energy is consumed during exercise.
“This decline in oxygen peak rate would roughly translate to a 40-year-old woman with an expected exercise capacity of 9.5 METs, dropping to 8.1 METs, the approximate expected exercise capacity for a 50-year-old woman,” Mr Durstenfeld said.
But it is important to note that this is an average, he added.
“Some individuals experience a profound decrease in energy capacity and many others experience no decrease.”
While researchers found “modest but consistent” evidence indicating people with long Covid have a reduced exercise capacity, they acknowledged a “low confidence in the magnitude of the effect”.
Noting the small study sizes, oversampling of patients in hospital and other factors, the authors argued that long-term observational studies should be conducted to understand “the trajectory of exercise capacity”.
Nearly one in five US adults who have had Covid-19 still have long Covid, a survey conducted by the Centres for Disease Control and Prevention showed.
