Kerri,
According to what I've read, the cramping is due to the affected muscle having been worn down and now is being overworked. My husband is having terrible cramps in his arms today, as he has been trying (bless his heart) to build a fence. His strength is less than mine and he is infuriated he cannot drive a nail! He just does not have the muscle available to do the work.
I suppose the muscle fibers that are left are being tested beyond their limit. I haven't read a definitive, scientific explanation though. Perhaps someone else knows more.
