Parkour consists of leaping, jumping, climbing, vaulting, and basically maneuvering over obstacles in an environment. Many tracuers (practitioners of parkour) tend to focus more on the obstacle, which is fun, but causes you to forget about another thing. Space. The philosophy behind parkour is to get to one point from another as quick as possible. If you are faced with an environment of open space, you must be a master of that too. You must be capable of running in vast open fields in all terrain. The space around an obstacle is just as important as the obstacle itself. To be able to move quickly in open space should be a priority to many tracuers.
To be able to run vast distances consistently is a priority in parkour. In many examples of parkour you will see people leap over gaps, and climb buildings. But what is most important is becoming aware of the space between, around, inside, and outside of these obstacles. Spatial awareness is the key to getting in touch with your environment. In order to run, leap, jump, vault or climb over things efficiently, you must be able to run, leap, and jump efficiently without an obstacle, before you actually attempt to do so over, around, under, or through an obstacle. When you attain efficiency in an environment without obstacles, becoming proficient in an obstacle-based environment will be much easier.
Running has many benefits that compliment parkour. It improves your cardiovascular system, coordination, endurance, it reduces the risk of bone and muscle loss. Runners are typically happier, less stressed out, and more confident. So start with jogging, on different terrain, sand, cement, dirt. Just as a good warm up, it reduces the chance of injury and stretches your muscles. I have yet to start myself.