The persistent fatigue that people with long-COVID experience is linked to the mitochondria in muscle cells producing reduced energy, according to a new study.
The findings by Dutch researchers from Amsterdam UMC and Vrije Universiteit Amsterdam (VU) show there are changes in the muscles of long-COVID patients – and it could pave the way for treatments, they say.
Professor Michèle van Vugt, professor of internal medicine at Amsterdam UMC, and his team assessed 25 long-COVID patients and 21 healthy control participants, who were asked to cycle for 15 minutes.
This cycling test caused a long-term worsening of post-exertional malaise (PEM) among the long-COVID cohort, they write in the latest edition of Nature Communications. The team looked at the blood and muscle tissue one week before the cycling test and one day after the test.
Rob Wüst, assistant professor at Department of Human Movement Sciences at the VU University, said: “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.
“So, the cause of the fatigue is really biological. The brain needs energy to think. Muscles need energy to move. This discovery means we can now start to research an appropriate treatment for those with long-COVID.”
The team dismissed theories that coronavirus particles remain in the body of people who have had COVID-19.
“We don’t see any indications of this in the muscles at the moment,” said Prof Van Vugt, adding they saw the heart and lungs functioned well in the patients, which means the long-lasting effect on patient’s fitness is not caused by abnormalities in the heart or lungs.
The researchers also concluded that exercising is not always beneficial for people with long-COVID.
Brent Appelman, researcher at Amsterdam UMC, advised that patients do not exceed their physical limits.
“Think of light exertion that does not lead to worsening of the complaints,” he said. “Walking is good, or riding an electric bike, to maintain some physical condition. Keep in mind that every patient has a different limit.”
Appelman B, Charlton BT, Goulding RP et al. Tiredness experienced by Long-COVID patients has a physical cause. Nature Communications 4 January 2024; doi: 10.1038/s41467-023-44432-3
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