Intense exercise might pose risks for long COVID patients, study finds

Exercise may harm those with long COVID, as intense activity can lead to severe tissue damage, a new study found.

People with long COVID often feel extra tired and in pain after mental or physical activities; this is known as post-exertional malaise, and a new study published in Nature Communications found that long COVID patients react very negatively to physical activity.

Dutch scientists conducted a study involving 25 long COVID patients and 21 healthy individuals, taking muscle biopsies before and after exercise.

The results revealed widespread problems in the tissue of long COVID patients, such as compromised mitochondria — which generate power at the cellular level — and insufficient energy. Additionally, tissue samples from long COVID patients showed severe muscle damage, a disrupted immune response, and an accumulation of microclots.

"Patients with long COVID displayed a markedly lower exercise capacity, which related to skeletal muscle metabolic alterations and a shift towards more fast-fatigable fibers," the researchers noted in the study. "The development of post-exertional malaise could in turn, however, lead to a further reduction in exercise capacity in patients, as the acute reduction in mitochondrial SDH activity, occurrence of tissue necrosis, and possibly intramuscular accumulation of amyloid-containing deposits could worsen skeletal muscle metabolism and force production over time, causing a vicious downward circle."

Looking closely at muscle tissue, scientists found that long COVID patients had smaller muscle fibers and a lot more cell death compared to healthy people. This means they end up with much more muscle damage in a shorter period of time.

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