I've been told that muscle tone starts to reduce after three days of not using them. I have seen this in action whenever I am away from the loom for more than a week.
It has been about 10 days since I've done any 'serious' weaving and I felt it when I got back to the loom today.
As I am only home for about two weeks before I leave again, I will no sooner get back to 'normal', then leave, this time for three weeks. While I will be taking a workshop during my trip, it won't be my usual sort of weaving. Then, once I'm home it will be all steam ahead in terms of show season. I hope I can fit at least a few days in, here and there, just to keep my hand in, as it were.
Because if you don't use it, you do, indeed, lose it.