I say it’s age, but it’s a mixture of age and the back problems I’ve had since my youth. My flexibility has been questionable for many years. One off move and a disk herniates. In some ways it was worse when I was younger and more flexible because I’d do or try to do things that my back couldn’t tolerate. At least now, with less flexibility and more wisdom, I don’t even try what used to put me in the emergency room or leave me bedridden for several days!