Long COVID Effects on Muscles and Post Exertional Fatigue

Medical News: Introduction to long COVID and muscle health
Since the COVID-19 pandemic began, scientists have observed that some patients continue to experience symptoms long after recovering from the initial infection. This condition, often called long COVID, affects roughly 10% of people infected with SARS-CoV-2, the virus that causes COVID-19. Symptoms can include fatigue, brain fog, muscle pain, and a unique condition known as post-exertional malaise (PEM). This Medical News report focuses on new research that examines the impact of long COVID on skeletal muscles and explains why people with long COVID often struggle with exercise and physical activities.

Long COVID Effects on Muscles and Post Exertional Fatigue
Schematic illustration of the five predominant mechanisms underlying long COVID skeletal muscle symptoms: local hypoxia, deconditioning, electrophysiological alterations, autoimmunity, and central fatigue. (A) Local hypoxia may be due to amyloid-containing clots (top panel), endothelial dysfunction (middle panel), or capillary thickening increasing oxygen diffusion distances (bottom panel). (B) Deconditioning results in muscle fiber atrophy, a loss of mitochondria, and capillary rarefaction, reducing aerobic capacity. (C) Electrophysiology may be altered by changes in ion distributions or effects on specific ion channels. (D) Generation of autoantibodies may target tissue receptors, including skeletal muscle. (E) Central fatigue may be caused by abnormal neurological processes, irregular responses to exercise, and feelings of myalgia and pain.

The study was conducted by a team of researchers from Vrije Universiteit Amsterdam, Amsterdam Movement Sciences Research Institute, Amsterdam UMC, and the Amsterdam Institute for Infection and Immunity in the Netherlands.
 
What is post-exertional malaise?
PEM refers to a worsening of symptoms after even minor physical or mental activities. People with PEM often feel drained for days or even weeks after exerting themselves. This condition is not exclusive to long COVID; it is also common in a condition called myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), which has similar symptoms. However, scientists are still trying to understand the exact cause of PEM and why it happens after physical activity.
 
The study sheds light on how skeletal muscle abnormalities could play a major role in the fatigue and PEM seen in long COVID.
 
Muscle changes in long COVID patients
One of the key findings of the study is that people with long COVID experience significant changes in their skeletal muscles, which are the muscles that help us move and maintain posture. These changes include:
 
-Mitochondrial dysfunction
Mitochondria are tiny structures within muscle cells that produce energy. In long COVID patients, the study found that mitochondrial function is impaired. This means their muscles struggle to produce enough energy, leading to faster fatigue and reduced exercise capacity. The researchers noted that some patients also showed changes in the size and structure of mitochondria, which might explain why their muscles are less efficient.
 
-Shift to glycolytic muscle fibers
Muscle fibers can be divided into two types: oxidative fibers (which use oxygen for energy and resist fatigue) and glycolytic fibers (which produce quick bursts of energy but tire easily). The study revealed that long COVID patients have a higher proportion of glycolytic muscle fibers, similar to what is seen in people with other chronic diseases. This shift may be contributing to the rapid fatigue experienced by long COVID patients.
 
-Endothelial abnormalities
The study also highlighted changes in the small blood vessels (capillaries) that supply oxygen and nutrients to the muscles. In some patients, the capillary-to-muscle fiber ratio was reduced, or the capillary walls became thicker. These changes can limit blood flow and oxygen delivery to muscles, leading to a condition known as local tissue hypoxia or oxygen deprivation.
 
Post-exertional malaise and muscle damage
One of the most striking findings of the study is how skeletal muscle health deteriorates after a period of physical exertion, particularly in those with PEM. Researchers conducted a two-day exercise test and analyzed muscle biopsies taken before and after exercise. The results showed a significant decline in mitochondrial activity and markers of muscle metabolism just one day after PEM-inducing exercise.
 
Interestingly, the muscle biopsies also revealed signs of inflammation and immune cell infiltration, suggesting that exercise triggers an immune response in the muscles of long COVID patients. This could explain why physical exertion worsens symptoms in these individuals.
 
Why are these findings important?
These findings provide a clearer picture of how long COVID affects skeletal muscles and helps explain why so many people with the condition struggle with exercise. Unlike healthy individuals, who benefit from regular physical activity, patients with long COVID often experience worsening symptoms after even mild exercise.
 
Potential causes of muscle dysfunction in long COVID
Researchers have proposed several possible explanations for these muscle abnormalities:
 
-Deconditioning: Some scientists believe that physical inactivity caused by prolonged illness leads to muscle weakness. However, the study found that muscle changes in long COVID are different from those seen in people who are simply inactive.
 
-Local hypoxia: Endothelial dysfunction and capillary blockages may cause reduced oxygen delivery to muscles, resulting in fatigue.
 
-Autoimmunity: There is growing evidence that long COVID may involve an autoimmune response, where the body’s immune system attacks its own tissues.
Electrophysiological changes: Abnormal sodium and calcium levels in muscle cells could impair mitochondrial function and cause early fatigue.
 
-Central fatigue: Neurological changes, such as brain inflammation and nerve damage, might contribute to the overall feeling of exhaustion and PEM.
 
Treatments and ongoing research
At present, there are no approved treatments specifically for long COVID. However, clinical trials are underway to explore potential therapies, including:
 
-Immunoadsorption therapy, which removes harmful antibodies from the blood.
 
-Dietary supplements, such as vitamin K2 and N-acetylcysteine, which may support mitochondrial health.
 
 -Anti-inflammatory and antiviral drugs, which aim to reduce inflammation and viral persistence
 
The researchers emphasize the need for more studies to understand how skeletal muscle abnormalities develop in long COVID and how they contribute to PEM. They also highlight the importance of finding new biomarkers and diagnostic tools to identify PEM and track disease progression.
 
Conclusions
This study highlights the significant impact of long COVID on skeletal muscle health, including mitochondrial dysfunction, endothelial changes, and a shift to glycolytic muscle fibers. These findings help explain why long COVID patients experience fatigue, muscle pain, and post-exertional malaise, even after mild physical activities. Unlike physical deconditioning caused by inactivity, the muscle changes seen in long COVID are unique and point to underlying mechanisms involving oxygen delivery, immune responses, and metabolic disruptions.
 
The researchers stress that more studies are needed to explore the link between endothelial dysfunction, mitochondrial changes, and PEM in long COVID. They also call for the development of new therapies that target these underlying issues, offering hope to millions of people affected by this condition worldwide.
 
The study findings were published in the peer reviewed journal: Trends in Endocrinology & Metabolism.
https://www.sciencedirect.com/science/article/pii/S1043276024002984
 
For the latest Long COVID news, keep on logging to Thailand Medical News.
 
Read Also:
https://www.thailandmedical.news/news/research-from-taiwan-shows-that-a-lychee-based-phytochemical-could-help-with-age-related-muscle-loss
 
https://www.thailandmedical.news/news/mechanisms-of-muscle-pain-in-long-covid
 
https://www.thailandmedical.news/news/covid-19-causes-muscle-atrophy