Researchers at Amsterdam UMC and Vrije Universiteit Amsterdam (VU) have discovered that the persistent fatigue experienced by patients with post-COVID has a physical cause. “We’re seeing changes in the muscles of these patients.” The study’s results were published today in *Nature Communications*.
Twenty-five patients with post-COVID and 21 healthy control participants took part in the study. All participants were required to perform a 15-minute cycling test. In people with post-COVID, this cycling test causes a prolonged worsening of symptoms, known as post-exertional malaise (PEM). PEM is characterized by extreme fatigue following physical, cognitive, or emotional exertion. The level of exertion at which PEM occurs is unknown and varies from person to person.
Less Energy
The researchers examined blood and muscle tissue one week before the cycling test and one day after the test. VU movement scientist Rob Wüst: “We observed various abnormalities in the patients’ muscle tissue. At the cellular level, we observed that the muscle’s mitochondria—also known as the cell’s powerhouses—were functioning less effectively and producing less energy.” Van Vugt adds: “The cause of the fatigue is therefore truly biological. Muscles need energy to move. Thanks to this discovery, we can now investigate what constitutes an effective treatment for people with post-COVID.”
One of the theories about post-COVID is that coronavirus particles remain in the bodies of people who have had the coronavirus. “We currently see no evidence of this in the muscles,” says Van Vugt. The researchers also observed that the patients’ hearts and lungs were functioning properly. The significantly reduced physical fitness is therefore not due to abnormalities in the heart or lungs.
Counterproductive
Exercise isn’t always good for patients with post-COVID. Brent Appelman, a physician-researcher specializing in infectious diseases at Amsterdam UMC: “Specifically, we advise these patients to be mindful of their physical limits and not to exceed them. Think of light exercise that does not lead to a worsening of symptoms. Walking is good, or riding an electric bike, to maintain physical fitness to some extent. Keep in mind that every patient has different limits.” Van Vugt warns: “Because symptoms can worsen after physical exertion, some traditional forms of rehabilitation and physical therapy can actually be counterproductive to these patients’ recovery.”
Post-COVID symptoms
Although the majority of people infected with the SARS-CoV-2 virus recover within a few weeks, a small group develops post-COVID. In addition to post-exertional malaise (PEM), symptoms in patients with post-COVID include severe cognitive problems (brain fog), fatigue, and exercise intolerance.