Fascinating stuff, thanks for the link. As for keeping active, I think my main danger has been that I keep trying to be too active rather than under active. I've not been very good at pacing myself and have a tendency to do too much too soon. And also a tendency to keep on going and pushing through pain.

It's highly possible that my 'outer' muscles are overcompensating. Certainly when I do high load stuff such as the walking down hill I can feel my superficial muscles tightening up esp a band of muscle running down my mid and lower spine and in my bum and thigh.