Researchers have found the biological causes of the fatigue felt by patients with long Covid, in particular mitochondrial dysfunction.
- Participants with long Covid have more white fibers in their muscles, which contain fewer mitochondria, organelles that participate in cell energy production.
- The mitochondria of people with long Covid did not function as well as those of healthy participants.
- The researchers also found that patients with long Covid had more tissue damage and signs of the body attempting to repair itself after the cycling session.
In France, around 2 million people continued to suffer from symptoms of Covid-19 several months after being infected with the virus at the end of 2022, according to Public health France. This is what we call long Covid, defined by theWorld Health Organization (WHO)like the “prolonged symptoms seen in some people after contracting Covid-19”.
Mitochondrial dysfunction explains fatigue
The reasons why some patients develop long Covid remain unclear. But a new study, published in the journal Nature Communications, allows us to better understand this phenomenon. Scientists have found biological causes of the fatigue felt by patients with long Covid.
Fatigue in patients with long Covid is generally intense after physical, cognitive or emotional effort. This is why the researchers wanted to put the participants in a tiring situation. To do this, they asked 25 people with long Covid and 21 people without this condition to cycle for 15 minutes.
To better assess the impact of this effort, they analyzed participants’ blood samples and muscle tissue one week before the cycling session and one day after.
First result: participants with long Covid had a greater proportion of white fibers in their muscles compared to healthy participants. These fibers have fewer mitochondria, organelles that participate in cell energy production.
Second observation: these mitochondria – already fewer in number in people with long Covid – did not function as well as those of healthy participants. According to the authors, this mitochondrial dysfunction can explain the participants’ lower resistance to exercise.
“We saw many abnormalities in patients’ muscle tissues, explains Rob Wüst, one of the authors of the study, in a communicated. At the cellular level, we have seen that muscle mitochondria, the cell’s energy sources, function less well and produce less energy.”
Physical exercise worsens symptoms in cases of long Covid
Scientists also observed that exercise was not beneficial in patients with long Covid. Indeed, after the cycling session, they had more tissue damage and signs of attempted body repair.
“This may explain, for example, the muscle pain these patients experience after exerciseexplains Rob Wüst, at Guardian. This damages your muscles, worsening your metabolism, which may explain why you experience muscle soreness and fatigue for up to weeks after exercising.“
