Former ME Research UK-funded researcher Prof. Dr Carmen Scheibenbogen and Prof. Dr Klaus Wirth summarised muscle research on individuals with ME/CFS, and those with long COVID with post-exertional malaise (PEM). The studies related to skeletal muscle (type of muscle that attaches to bone and helps with movement).
Main skeletal muscle findings –
Muscle fatigue, weakness and other clinical signs
- Individuals with ME/CFS, and those with long COVID, experience “Fatigue, early exhaustion, muscle weakness, muscle pain, fasciculations and cramps”.
- Hand grip strength is reduced and correlates with symptom severity and prognosis.
Exercise and energy problems during exercise
- Patients’ bodies switch to anaerobic metabolism (less efficient energy production) earlier.
- There is “Diminished oxygen uptake and extraction” (body has trouble absorbing oxygen and using it efficiently).
Muscle damage and mitochondrial issues
- Muscle biopsies show damage, inflammation, and signs of regeneration, after exercise.
- Mitochondria (energy-producing organelles found in cells) do not work properly, and there is potential damage.
- The shape and structure of mitochondria may be abnormal at times.
Sodium and calcium imbalance
- One study, which Prof. Dr Scheibenbogen and Prof. Dr Wirth were involved in, found elevated intracellular (inside cells) sodium in patients’ muscle cells with a negative correlation with hand grip strength.
- According to the review – “Rise in intracellular sodium is a precondition for damaging calcium overload”.
Conclusion
People with ME/CFS, and those with long COVID, experience muscle weakness, muscle fatigue, and exercise intolerance, amongst other symptoms. Studies suggest this is linked to problems such as mitochondria in muscle not working properly, muscle damage, and problems using oxygen for energy. Some patients also show inflammation and nerve issues in their muscles.
However, as with much research in an under-funded field such as ME/CFS, many studies were small, hence more research is needed. Future studies should include more patients, longer follow-ups, and attempt to replicate findings, in order to gain a better understanding of what is happening in the muscles of individuals with ME/CFS.
Read Cort Johnson’s exploration of muscle abnormalities identified in ME/CFS research
