This may be a stupid question, but while reading researchers explain how inactivity leads to a vicious cycle of fatigue and pain/symptoms, I haven't actually seen them cite published evidence that this is true - is there any? I've seen lots of assertions but no concrete evidence. There's some evidence that it plays a role in chronic pain but I've seen nothing that could explain chronic pain completely (or even substantially). If there is any evidence, could someone point me to it. Thanks. ps not a sarcastic question, I am genuinely interested but puzzled by how hard it is to find any such evidence.