Researchers find fatigue felt by long-term COVID patients has a physical cause

Researchers from UMC Amsterdam and Vrije Universiteit Amsterdam (VU) have discovered that persistent fatigue in long COVID patients has a biological cause, namely the mitochondria of muscle cells which produce less energy than in healthy patients. The results of the study were published in Natural communications.

“We see obvious changes in the muscles of these patients,” explains Michèle van Vugt, professor of internal medicine at UMC Amsterdam.

A total of 25 long-COVID patients and 21 healthy control participants participated in the study. They were asked to cycle for 15 minutes. This cycling test caused long-term worsening of symptoms in people with long COVID, called post-exertional malaise (PEM). Extreme fatigue occurs after physical, cognitive or emotional effort beyond an unknown individual threshold. The researchers examined blood and muscle tissue one week before the cycling test and one day after the test.

“We found various abnormalities in the muscle tissue of patients. At the cellular level, we found that the muscle’s mitochondria, also called the cell’s energy factories, function less well and produce less energy,” explains Rob . Wüst, assistant professor at the Department of Human Movement Sciences at VU University.

“So the cause of fatigue is actually biological. The brain needs energy to think. Muscles need energy to move. This discovery means we can now start looking for a suitable treatment for people with fatigue. “a long COVID,” adds van Vugt.

One of the theories about long COVID is that coronavirus particles may remain in the bodies of people who have had the coronavirus. “We currently don’t see any signs of this in the muscles,” says Van Vugt. The researchers also found that the patients’ hearts and lungs worked well. This means that the long-term effect on the patient’s physical condition is not due to cardiac or pulmonary abnormalities.

Exercising within your own limits

Exercising is not always good for patients with long COVID. “Concretely, we advise these patients to keep their physical limits and not exceed them. Consider light efforts that do not lead to worsening of symptoms. Walking is good, or riding an electric bike, to maintain a certain physical condition. Keep in mind that each patient has a different limit,” explains Brent Appelman, researcher at UMC Amsterdam.

“As symptoms can worsen after physical exertion, some conventional forms of rehabilitation and physiotherapy are counterproductive to the recovery of these patients,” adds van Vugt.

Long symptoms of COVID

Although the majority of people infected with the SARS-CoV-2 virus recover within a few weeks, a subgroup, estimated at around one in eight people, will experience long COVID. Symptoms in patients with long COVID, post-acute aftereffects, or COVID or post-COVID syndrome (PCS) include severe cognitive problems (brain fog), fatigue, exercise intolerance, autonomic dysregulation , postural orthostatic tachycardia syndrome (POTS), orthostatic intolerance, and worsening of symptoms after PEM.

Provided by the University of Amsterdam Medical Center