Britannica: Muscle Disease Pathology

This is one of the best overviews of pathologies of muscle disease, disorders, and weakness. Written by Walter G. Bradley, Richard Humphrey, Tudor Edwards, and Ronald A. Henson. It's well written so that most who are not medical professionals can follow. I hope you read it! The section over muscle nerves and neurons explains a lot about how weakness is not simply a result of overexertion. I really wish all of this was taught to musicians as a part of their education. Not only is it important, but I find it rather fascinating in general.

https://www.britannica.com/science/muscle-disease?fbclid=IwAR0lkrLChFbcz-p7SUp9abuV6DqTwge62PNu6A3gKnWuj9H3Bj65wPgHrgc