Hey Gomicho,

Something you may wish to explore is a mitochondrial disorder of some kind. The Chronic Fatigue Syndrome blog/website Health Rising is an excellent resource with respect to this.

Something else you may consider is Mestinon a drug for Myasthenia Gravis. Using it off label may be appropriate for you, certainly worth exploring.

mestinon for pn?

A Mestinon Miracle: Vagus Nerve Stimulating Drug Helps Long Time ME/CFS Patient Exercise - Health Rising

Do you have any weakness in your legs at all or is it purely your arms? And is it only some muscles? And do they ache, hurt, get tired simultaneously?

Best wishes,

Atty