Muscle fatigue and pain are key symptoms of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Although the pathophysiology is not yet fully understood, there is ample evidence for hypoperfusion which may result in electrolyte imbalance and sodium overload in muscles.
After 5 years experimenting drugs, I had the evidences that peripheral hypoperfusion drives pain and weakness, both in muscles and in the low back.
My blood pressure is naturally low, and each time I happened to take a drug lowering blood pressure, hypotension increased pain (and muscle weakness) in my legs and low back.
It happened both with Beta Blockers and with AT1R blockers.
Women are more prone to low blood pressure and this is the reason why they experience more these symptoms.
Women also suffer more from iron deficiency and this is a common cause for low dopamine in the brain and central hyperalgia and exercice intolerance.
Any disease that lower blood volume will induce some degree of hypoperfusion in muscles and some part of the brain and produce the kind of symptoms we observe in Fibro and ME/CFS.
The question would be: are the GPCR autoantibodies observed in ME/CFS a body reaction to fight the peripheral hypoperfusion or are they causative?