The other day I hurt my back. I wasn’t moving furniture or playing football. I was picking up a towel that had fallen on the floor. It was only a momentary twinge of pain, but I knew that in a few hours those muscles would start to tighten and I’d be paying for the mundane thing I had just done. My body used to take so much abuse with only minor complaints. Age has a way of settling up old debts. And while I can complain to Dr. Kelly about the stiffness or soreness, Raylan, our 9 year old lab cannot. He plods along whether we notice him moving slower or not.    What is it about getting older that makes us all just a bit more… fragile?  You’ve likely heard the common refrain, age isn’t a disease, but many of us have also internalized the idea of dying from old age if not from “natural causes,” whatever that means. So which is it? Is it a disease process or not? And if not, why does it bring so much disease in its wake? When we look at our dog or cat with the graying muzzle who suddenly has so many issues where for so long there were none, we can’t help but ask, what changed? The nuts and bolts of this answer are stunningly complicated and even now our collective understanding of all of the mechanisms involved are limited.