Post-Covid fatigue not just caused by inactivity, study finds

Patients with post-Covid syndrome suffer muscle damage that cannot be fully be explained by inactivity, research led by scientists at Amsterdam’s Vrije Universiteit (VU) has found.

The team compared the blood and muscle tissue of patients with long Covid and chronic fatigue (ME) with a group of healthy people who spent 60 days in bed as part of a study simulating the effects of space travel.

The post-Covid and ME patients had suffered from energy dips that caused them to avoid exercising or spend long periods in bed, which has a degrading impact on the skeletal muscles.

But the researchers, led by Rob Wüst, a movement scientist at the VU, found differences in the colour of the muscle fibres between the two groups, indicating that the post-Covid patients had a much lower oxygen capacity.

“As skeletal muscle characteristics differ between patients and healthy individuals after bed rest, physical inactivity cannot solely explain the lower exercise capacity and skeletal muscle adaptations in long Covid and ME/CFS patients,” they wrote in a paper published in Nature Communications.

The healthy individuals from the space programme still had bright red fibres, which are still oxygen-rich, while the patients had white fibres, which become exhausted much faster.

Rapid tiredness

The researchers said the difference could explain why post-Covid and ME sufferers become tired so quickly even after modest levels of exercise or exertion. “The redder the fibres, the more stamina a person has,” Wüst explained.

Lung specialist Merel Hellemons, of the Erasmus MC teaching hospital in Rotterdam, told the Volkskrant that the findings were a crucial development in understanding how to treat patients with conditions such as post-Covid syndrome.

“Many patients hear that they need to move more or that being less active is bad for them,” she said.

Wüst said patients should still be encouraged to be more mobile to avoid damage to their muscles, skeletons and cardiovascular system caused by inactivity. “The question is: what is possible? We need more tailored solutions,” he said.