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THURSDAY, Jan. 4, 2023 (HeathDay News) -- Muscle cells' "power stations" function less effectively in people with long COVID, potentially explaining the persistent fatigue that's a hallmark of the condition.
That's the finding of a Dutch study published Jan. 4 in the journal Nature Communications.
"We're seeing clear changes in the muscles in these patients," said study lead author Michèle van Vugt, a professor of internal medicine at Amsterdam University Medical Center (UMC).
According to background information from the researchers, about one in every eight COVID patients will go on to experience long COVID. Symptoms can last for months and include fatigue, problems with memory and thinking, and other issues.
In the study, van Vugt's group examined the muscle cells of 25 long COVID patients and 21 healthy people.
They had all of the participants engage in a 15-minute bout of cycling. In folks with long COVID, this burst of exercise led to a transient worsening of their symptoms.
The researchers examined participants' blood and muscle tissue at two time points: One week before the cycling test and one day afterwards.
"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 study co-author Rob Wüst, an assistant professor of human movement sciences at Vrije University, in Amsterdam.
"So, the cause of the fatigue is really biological," Wüst said in a UMC news release. "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."
Could coronavirus lingering in muscle tissue be causing all this?
"We don't see any indications of this in the muscles at the moment," Van Vugt noted.
The team also saw no decline in heart or lung function, suggesting the issue with fatigue is not originating in those organs.
Could exercise help patients fight long COVID fatigue?
"In concrete terms, we advise these patients to guard their physical limits and not to exceed them," said Brent Appelman, a researcher at Amsterdam UMC. "Think of light exertion that does not lead to worsening of the complaints. Walking is good, or riding an electric bike, to maintain some physical condition. Keep in mind that every patient has a different limit."
Van Vugt agreed.
"Because symptoms can worsen after physical exertion, some classic forms of rehabilitation and physiotherapy are counterproductive for the recovery of these patients," she said.
Find out more about long COVID at Yale Medicine.
SOURCE: Amsterdam University Medical Center, news release, Jan. 4, 202