I can probably only speak for me but I heard similar things from other people. I have a certain point after I didn't do anything for a few days when my body or brain tells me to move. I want to go outside or do some kettlebell workout. I can tell most people have this feeling. I've read a book where exactly was described how the body is made for moving and even every cell is made for moving. You are just not used to it but your body is made for it. Pain will get better and most therapists will tell you that moving will help to get rid of pain or even lower it. I'm not a therapist but I'm an ambition ed fitness trainer who learned much more as he should be when he went to exam. I would like to work in this area but you don't earn much unfortunately. On the other side there is my wife who became a geriatric nurse and she will tell you the same especially when it is about age. 
Sorry for holding a dialog but this is a topic which is always important for me. 
!BBH !ALIVE