You are probably not as outnumbered in age as you might think... PK is accessible to anyone! We had a guy in his mid 50's training with us on a regular basis! Like everyone else, you've got to start small and progress wisely. Progression is the key to everything we do!
First, get used to moving again. Learn to explore your environment with new eyes, the way a child moves around a jungle gym. Don't worry about technique's or "moves" just yet. Seek out obstacles and interact with them. Figure out how to overcome them using your bodies natural abilities(Running, Jumping, Climbing, Quadrupedal Movement). Adapt yourself to the obstacle and make yourself stronger in the process. Remember, your movements should be building up your body and not wearing it down.
The next step is learning proper bio mechanics. How do we jump? How do we land safely? What kinds of injuries are common in Parkour and how can we prevent them? Read everything you can get your hands on and don't be afraid to ask questions. Online and Local communities are invaluable for this. Get in touch with more experienced practitioners.
Finally, practice makes perfect. As your skill increases, the risks you take should decrease. We want to perfect our movement in order to eliminate risk. The real skill is in the precision of the movement, not the size of the obstacle.
