Stress makes you tired. It's very common for people under any kind of stress to feel exhausted. I don't think nerves get 'tired' - muscles do, but it is common for twitching in any person (or other mammals as I see it in pets also) to increase when tired (bfs or not). Another aspect is lack of circulation from being sedentary - this keeps the body from eliminating wastes, etc. Exercise seems to cure me of this to some degree when its due to non-physical work load although it is sometimes hard to pull yourself together to exercise when you are exhausted from a long day at work or not sleeping enough. Even a little stretching seems to help. If it's from physical work I'd stick with stretching myself. It's not a theory, it's just my little personal experience. I wish everyone would stop using that word incorrectly - a theory has proven research behind it that has been tested over time. Hypothesis is a better word - an explanation of observed phenomenon.