No you’re not. I’m 52 and can still just about move 🤣 - takes a little more time to build up from a break compared to when younger. Regular walking is great for this and over a decent distance. Then build up the pace and turn it into a power walk/jog. Swimming also great in between to promote/keep the flexibility and take the pressure off the joints. (Recovery). Injury often a result of overdoing it/technique.