Researchers Link Fatigue from Long-COVID to Changes in Muscles

2 min read

Jan. 10, 2024 -- People with long-COVID suffer from persistent fatigue that new research from Amsterdam attributes to changes in the muscles.

Scientists from Amsterdam UMC and Vrije Universiteit Amsterdam (VU) say the fatigue is caused by mitochondria in muscle cells that produce less energy than in healthy people, according to a press release on EurekAlert.

The results of the study were published in Nature Communications.

Michèle van Vugt, professor of internal medicine at Amsterdam UMC, said, “We’re seeing clear changes in the muscles in these patients.”

The study involved 25 people with long-COVID and 21 healthy people. They were asked to cycle for 15 minutes, which caused worse symptoms in those with long-COVID, or post-exertional malaise (PEM).

National Public Radio reports that while most people are sore after exercise, PEM is different. "It's not just soreness," study co-author Braeden Charlton told NPR. "For a lot of people, it's completely debilitating for days to weeks."

Scientists examined blood and muscle tissue a week before the cycling and a day after it.

"We saw various abnormalities in the muscle tissue of the patients. At the cellular level, we saw that the mitochondria of the muscle, also known as the energy factories of the cell, function less well and that they produce less energy," said Rob Wüst, assistant professor in human movement sciences at the VU. "So, the cause of the fatigue is really biological … This discovery means we can now start to research an appropriate treatment for those with long-COVID.”

Researchers said their findings contradict a theory about long-COVID – that coronavirus particles stay in the body. They also said that heart and lungs functioned well, which means that long-term effects on fitness are not caused by problems with the heart and lungs.