I turned 40 last November and have no issues. But one thing I do believe that has contributed to that is that I cycle my workouts. I have posted a more detailed explaination a couple of times before, but the gist of it is that train heavy Jan - March very similar to the program that Phil Hernon taught and sold, then I add more volume and slightly up the reps from April to the end of October. November and December, I don't train. I mean, I remain active - doing a lot of walking and riding my bike extensively along the beach since the weather is nice. And some flexibility work and soft tissue work from the ART that rents out of my wife's office, but no direct weight training.
One of gifts we received from friends at our wedding last month was a gift book of 20 sixty minute passes to this StretchZone business. Where they do assisted stretching and such. I've never been but looking forward to it.
I'll try to find a prior post.